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Do we need Dietary supplements..? You decideinformation on supplements and nutrients
ZINC MANGANESE COPPER SELENIUM VITAMIN C VITAMIN E BETA-CAROTENE LUTEIN LYCOPENE VITAMIN B2 coenzyme q10 cysteine bilberry turmeric ginkgo biloba CANCER DIABETES VITAMIN C and DIABETES ATHEROSCLEROSIS
What does it do? Zinc is a component of more than 300 enzymes needed to repair wounds, maintain fertility in adults and growth in children, synthesize protein, help cells reproduce, preserve vision, boost immunity, and protect against free radicals, among other functions. In double-blind trials, zinc lozenges have reduced the duration of colds in adults, but have been ineffective in children. The ability of zinc to shorten colds may be due to a direct, localized anti-viral action in the throat. For the alleviation of cold symptoms, lozenges providing 13–25 mg of zinc, in the form of zinc gluconate, zinc gluconate-glycine, or zinc acetate, are used, typically every two hours while awake, but only for several days. The best effect is obtained when lozenges are used at the first sign of a cold. Lozenges containing zinc gluconate, zinc gluconate-glycine, or zinc acetate have been effective, whereas most other forms of zinc and lozenges flavored with citric acid, tartaric acid, sorbitol, or mannitol, have been ineffective. Trials using forms other than zinc gluconate, zinc gluconate-glycine, or zinc acetate have failed, as have trials that use insufficient amounts of zinc. Therefore, until more is known, people should only use zinc gluconate, zinc gluconate-glycine, or zinc acetate. Zinc reduces the body’s ability to utilize the essential mineral copper. (For healthy people, this interference is circumvented by supplementing with copper, along with zinc.) The ability to interfere with copper makes zinc an important therapeutic tool for people with Wilson’s disease—a genetic condition that causes copper overload. Zinc supplementation in children in developing countries is associated with improvements in stunted growth, increased weight gain in underweight children, and substantial reductions in the rates of diarrhea and pneumonia, the two leading causes of death in these settings. Whether such supplementation would help people in better nourished populations remains unclear.
A small, preliminary trial has found zinc sulfate to be effective for contact dermatitis (a skin rash caused by contact with an allergen or irritant).
Participants with active skin rashes took approximately 23 mg of zinc (in the form of zinc sulfate) three times daily, for one month. 73% of those taking the zinc sulfate had complete resolution of their skin rashes, while the remaining participants had a 50–75% improvement. Further trials are needed to confirm these preliminary findings, however. Where is it found? Good sources of zinc include oysters, meat, eggs, seafood, black-eyed peas, tofu, and wheat germ. Who is likely to be deficient? Zinc deficiencies are quite common in people living in poor countries. Phytate, a substance found in unleavened bread (pita, matzos, and some crackers) significantly reduces absorption of zinc, increasing the chance of zinc deficiency. However, phytate-induced deficiency of zinc appears to be a significant problem only for people already consuming marginally low amounts of zinc.
Even in developed countries, low-income pregnant women and pregnant teenagers are at risk for marginal zinc deficiencies. Supplementing with 25–30 mg per day improves pregnancy outcome in these groups. People with liver cirrhosis appear to be commonly deficient in zinc. This deficiency may be due to cirrhosis-related zinc malabsorption. People with Down’s syndrome are also commonly deficient in zinc. Giving zinc supplements to children with Down’s syndrome has been reported to improve impaired immunity and thyroid function, though optimal intake of zinc for people with Down’s syndrome remains unclear.
Children with alopecia areata (patchy areas of hair loss) have been reported to be deficient in zinc. The average diet frequently provides less than the Recommended Dietary Allowance for zinc, particularly in vegetarians. To what extent (if any) these small deficits in zinc intake create clinical problems remains unclear. Nonetheless, a low-potency supplement (15 mg per day) can fill in dietary gaps. Zinc deficiencies are more common in alcoholics and people with sickle cell anemia, malabsorption problems, and chronic kidney disease. How much is usually taken? Moderate intake of zinc, approximately 15 mg daily, is adequate to prevent deficiencies. Higher levels (up to 50 mg taken three times per day)are reserved for people with certain health conditions, under the supervision of a doctor.
For the alleviation of cold symptoms, lozenges providing 13–25 mg of zinc in the form zinc gluconate, zinc gluconate-glycine, or zinc acetate are generally used frequently but only for several days. Are there any side effects or interactions? Zinc intake in excess of 300 mg per day has been reported to impair immune function. Some people report that zinc lozenges lead to stomach ache, nausea, mouth irritation, and a bad taste. One source reports that gastrointestinal upset, metallic taste in the mouth, blood in the urine and lethargy can occur from chronic oral zinc supplementation over 150 mg per day, but those claims are unsubstantiated. In topical form, zinc has no known side effects when used as recommended.
Preliminary research had suggested that people with Alzheimer’s disease should avoid zinc supplements. More recently, preliminary evidence in four patients actually showed improved mental function with zinc supplementation. In a convincing review of zinc/Alzheimer’s disease research, perhaps the most respected zinc researcher in the world concluded that zinc does not cause or exacerbate Alzheimer’s disease symptoms.
Zinc inhibits copper absorption. Copper deficiency can result in anemia, lower levels of HDL (“good”) cholesterol, or cardiac arrhythmias. Copper intake should be increased if zinc supplementation continues for more than a few days (except for peoplewith Wilson’s disease). Some sources recommend a 10:1 ratio of zinc to copper. Evidence suggests that no more that 2 mg of copper per day is needed to prevent zinc-induced copper deficiency. Many zinc supplements include copper in the formulation to prevent zinc-induced copper deficiency. Zinc-induced copper deficiency has been reported to cause reversible anemia and suppression of bone marrow. Marginal zinc deficiency may be a contributing factor in some cases of anemia. In a study of women with normocytic anemia (i.e., their red blood cells were of normal size) and low total iron-binding capacity (a blood test often used to assess the cause of anemia), combined iron and zinc supplementation significantly improved the anemia, whereas iron or zinc supplemented alone had only slight effects. Supplementation with zinc, or zinc and iron together, has been found to improve vitamin A status among children at high risk for deficiency of the three nutrients. Zinc competes for absorption with copper, iron, calcium and magnesium. A multimineral supplement will help prevent mineral imbalances that can result from taking high amounts of zinc for extended periods of time.
N-acetyl cysteine (NAC) may increase urinary excretion of zinc. Long-term users of NAC may consider adding supplements of zinc and copper.
Are there any drug interactions? Certain medications may interact with zinc. Refer to the drug interactions safety check for a list of those medications.
What does it do? Manganese is needed for healthy skin, bone, and cartilage formation, as well as glucose tolerance. It also helps activate superoxide dismutase (SOD)—an important antioxidant enzyme.
Where is it found? Nuts and seeds, wheat germ, wheat bran, leafy green vegetables, beet tops, tea, and pineapple are all good sources of manganese.
Who is likely to be deficient? Many people consume less than the 2–5 mg of manganese currently considered safe and adequate. Nonetheless, clear deficiencies are rare. People with osteoporosis sometimes have low blood levels of manganese, suggestive of deficiency. How much is usually taken? Whether most people would benefit from manganese supplementation remains unclear. While there is no recommended dietary allowance, the National Research Council’s “estimated safe and adequate daily dietary intake” is 2–5 mg.2 The Institute of Medicine recommends that intake of manganese from food, water and dietary supplements should not exceed the tolerable daily upper limit of 11 mg per day. In contrast, the 5–15 mg often found in high-potency multivitamin-mineral supplements is generally considered to be a reasonable level by many doctors, though many manufacturers are likely to reformulate their products to contain no more than 11 mg per daily amount.
Are there any side effects or interactions? Amounts found in supplements (5–20 mg) have not been linked with any toxicity. Excessive intake of manganese rarely lead to psychiatric symptoms. However, most reports of manganese toxicity in otherwise healthy people have been in those people who chronically inhaled manganese dust at their jobs e.g., miners or alloy plant workers. Other sources of manganese intoxication are now recognized, including total parenteral nutrition (TPN) in patients who are being fed intravenously and pesticides containing manganese in agricultural workers who have been exposed. Preliminary research suggests that people with cirrhosis7 or cholestasis (blocked bile flow from the gall bladder) may not be able to properly excrete manganese. Until more is known, these people should not supplement manganese. Manganese supplementation (3–5 mg per day) has caused severe hypoglycemia (low blood sugar) in a person with insulin-dependent diabetes. People with diabetes who want to take manganese should consult their doctor.
Several minerals, such as calcium and iron, and possibly zinc, reduce the absorption of manganese. Of these interactions, the link to iron may be the most important. In one study, women with high iron status had relatively poor absorption of manganese. In another report of manganese/iron interactions in women, increased intake of “non-heme iron”—the kind of iron found in most supplements—decreased manganese status.
These interactions suggest that taking multi-minerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated mineral supplements, particularly iron.
Are there any drug interactions? Certain medications may interact with manganese. Refer to the drug interactions safety check for a list of those medications.
What does it do? Where is it found? Copper has been used in connection with the following conditions Who is likely to be deficient? Many people consume slightly less than the “safe and adequate range” of copper, 1.5–3.0 mg per day. How much is usually taken? Cupric oxide (CuO) is a form of copper frequently used in vitamin-mineral supplements sold over-the-counter. However, animal studies have shown conclusively this form of copper is poorly absorbed from the gut; it should therefore not be used in supplements. Zinc interferes with copper absorption. People taking zinc supplements for more than a few weeks should also take copper (unless they have Wilson’s disease). Preliminary evidence shows that the levels of copper in the blood were higher among people who died from coronary heart disease than among those who did not. What does it do? In a double-blind trial, selenium supplementation of infertile men improved the motility of sperm cells and increased the chance of conception.
Who is likely to be deficient? Are there any side effects or interactions? Selenium is safe at the level people typically supplement (100–200 mcg); however, taking more than 900 mcg of selenium per day has been reported to cause adverse effects in some people. Are there any drug interactions? Certain medications may interact with selenium.
What does it do? Vitamin C may help protect the body against accumulation or retention of the toxic mineral, lead. Where is it found? Who is likely to be deficient? The studies that ascertained approximately 120–200 mg daily of vitamin C is correct for prevention purposes in healthy people have typically not investigated whether people suffering from various diseases can benefit from larger amounts. What does it do? Vitamin E is an antioxidant that protects cell membranes and other fat-soluble parts of the body, such as LDL cholesterol (the “bad” cholesterol), from damage. Only when LDL is damaged does cholesterol appear to lead to heart disease, and vitamin E is an important antioxidant protector of LDL. Several studies, including two double-blind trials, have reported that 400 to 800 IU of natural vitamin E per day reduces the risk of heart attacks. However, other recent double-blind trials have found either limited benefit, or no benefit at all from supplementation with synthetic vitamin E. One of the negative trials used 400 IU of natural vitamin E8 —a similar amount and form to previous successful trials. In attempting to make sense of these apparently inconsistent findings, the following is clear: less than 400 IU of synthetic vitamin E, even when taken for years, does not protect against heart disease. Whether 400 to 800 IU of natural vitamin E is, or is not, protective remains unclear. Vitamin E also plays some role in the body’s ability to process glucose. Some, but not all, trials suggest that vitamin E supplementation may eventually prove to be helpful in the prevention and treatment of diabetes. In the last ten years, the functions of vitamin E in the cell have been further clarified. In addition to its antioxidant functions, vitamin E is now known to act through other mechanisms, including direct effects on inflammation, blood cell regulation, connective tissue growth, and genetic control of cell division. Where is it found? Wheat germ oil, nuts and seeds, whole grains, egg yolks, and leafy green vegetables all contain vitamin E. Certain vegetable oils should contain significant amounts of vitamin E. However, many of the vegetable oils sold in supermarkets have had the vitamin E removed in processing. The high amounts found in supplements, often 100 to 800 IU per day, are not obtainable from eating food. Who is likely to be deficient? Severe vitamin E deficiencies are rare. People with a genetic defect in a vitamin E transfer protein called thrombotic thrombocytopenic purpura (TTP) have severe vitamin E deficiency, characterized by low blood and tissue levels of vitamin E and progressive nerve abnormalities. Low vitamin E status has been associated with an increased risk of rheumatoid arthritis and major depression. Women with preeclampsia have been found to have lower blood levels of vitamin E than women without the condition. Very old people with type 2 diabetes have shown a significant age-related decline in blood levels of vitamin E, irrespective of their dietary intake. Which form is best? The names of all types of vitamin E begin with either “d” or “dl,” which refer to differences in chemical structure. The “d” form is natural (also known as RRR-alpha tocopherol) and “dl” is synthetic (more correctly known as all-rac-alpha tocopherol). The natural form is more active and better absorbed. Little is known about how the “unnatural”“l” portion of the synthetic “dl” form affects the body, though no clear toxicity has been discovered. In theory, when a vitamin E supplement is labeled “400 IU” it should have the same level of activity regardless of its source. This is purportedly achieved by using more synthetic vitamin E to reach the same potency as a lesser amount of natural vitamin E. For example, 100 IU of vitamin E requires about 67 mg of the natural form but closer to 100 mg of the synthetic. However, a recent review of the scientific evidence suggests that natural vitamin E probably has greater activity in the body than indicated on the label. Natural vitamin E may be as much as twice as bioavailable as synthetic vitamin E, not 1.36 times as is generally accepted. Many doctors advise people to use only the natural, the “d” form, of vitamin E. After the “d” or “dl” designation, often the Greek letter “alpha” appears, which also describes the structure. Synthetic “dl” vitamin E is found only in the alpha form—as in “dl-alpha tocopherol.” Natural vitamin E may be found either as alpha—as in “d-alpha tocopherol”—or in combination with beta, gamma, and delta, labeled “mixed”—as in mixed natural tocopherols. Little is known about the importance of the beta and delta forms of vitamin E, but a debate has arisen concerning gamma tocopherol. In a test tube study, gamma tocopherol was found to be more effective than alpha tocopherol in protecting against certain specific types of oxidative damage. In addition, some researchers have hypothesized that alpha tocopherol might interfere with the activity of gamma tocopherol, although this idea remains unproven. Human trials with vitamin E have almost always been done with the alpha (not gamma) form. Historically the synthetic “dl” form was used in most trials, but some trials are now using the natural form. The issue of alpha vs. gamma form requires more research before it can be fully understood. Almost all vitamin E research shows that, when positive results are obtained, hundreds of units per day are required—an amount easily obtained with supplements but impossible with food. Therefore, switching to food sources, as suggested by some researchers, is impractical. On the other hand, the vitamin E occurring naturally in food contains gamma tocopherol and other tocopherols. Thus, it possibly may turn out to be more effective than the vitamin E taken in supplement form. Additional research is needed in this area. Vitamin E forms are listed as either plain “tocopherol” or tocopheryl followed by the name of what is attached to it, as in “tocopheryl acetate.” The two forms are not greatly different. However, plain tocopherol may be absorbed a little better, while tocopheryl attached forms have a slightly better shelf life. Both forms are active when taken by mouth. However, the skin utilizes the tocopheryl forms very slowly, so those planning to apply vitamin E to the skin should buy plain tocopherol. In health food stores, the most common forms of vitamin E are d-alpha tocopherol and d-alpha tocopheryl acetate or succinate. Both of these d (natural) alpha forms are frequently recommended by doctors. Although the succinate form is slightly weaker than the acetate form, more milligrams of the succinate form are added to supplements to compensate for this small difference in potency. Therefore, 400 IU of either form should have equivalent potency. How much is usually taken? The recommended dietary allowance for vitamin E is low, just 15 mg or approximately 22 International Units (IU) per day. The most commonly recommended amount of supplemental vitamin E for adults is 400 to 800 IU per day. However, some leading researchers suggest taking only 100 to 200 IU per day, since trials that have explored the long-term effects of different supplemental levels suggest no further benefit beyond that amount. In addition, research reporting positive effects with 400 to 800 IU per day has not investigated the effects of lower intakes. For tardive dyskinesia, the best results have been achieved from 1,600 IU per day, a large amount that should be supervised by a healthcare practitioner. Are there any side effects or interactions? Vitamin E toxicity is very rare and supplements are widely considered to be safe. The National Academy of Sciences has established the daily tolerable upper intake level for adults to be 1,000 mg of vitamin E, which is equivalent to 1,500 IU of natural vitamin E or 1,100 IU of synthetic vitamin E. In contrast to trials suggesting vitamin E improves glucose tolerance in people with diabetes, one trial reported that 600 IU per day of vitamin E led to impairment in glucose tolerance in obese people with diabetes. The reason for the discrepancy between reports is not known. Patients on kidney dialysis who are given injections of iron frequently experience “oxidative stress.” This is because iron is a pro-oxidant, meaning that it interacts with oxygen molecules in ways that may damage tissues. These adverse effects of iron therapy may be counteracted by supplementation with vitamin E. A diet high in unsaturated fat increases vitamin E requirements. Vitamin E and selenium work together to protect fat-soluble parts of the body. Are there any drug interactions? Certain medications may interact with vitamin E.
What does it do? Beta-carotene is a substance from plants that the body converts into vitamin A. It also acts as an antioxidant and an immune system booster. Other members of the antioxidant carotenoid family include cryptoxanthin, alpha-carotene, zeaxanthin, lutein, and lycopene. However, unlike beta-carotene, most of these nutrients are not converted to vitamin A in significant amounts. Where is it found? Dark green and orange-yellow vegetables are good sources of beta-carotene. It is also available in supplements. Who is likely to be deficient? People who limit their consumption of beta-carotene-containing vegetables could be at higher risk of developing a vitamin A deficiency. However, because beta-carotene is not an essential nutrient, true deficiencies do not occur. Nevertheless, very old persons with type 2 diabetes have shown a significant age-related decline in blood levels of carotenoids, irrespective of their dietary intake. Which form is best? Most beta-carotene in supplements is synthetic, consisting of only one molecule called all trans beta-carotene. Natural beta-carotene, found in food, is made of two molecules—all trans beta-carotene and 9-cis beta-carotene. Researchers originally saw no meaningful difference between natural and synthetic beta-carotene. This view was questioned when the link between beta-carotene-containing foods (all natural) and lung cancer prevention was not duplicated in studies using synthetic pills. In smokers, synthetic beta-carotene has apparently caused an increased risk of lung cancer and disease of the blood vessels in double-blind research. Animal research has begun to identify the ways in which synthetic beta-carotene might cause damage to lungs, particularly when animals are exposed to cigarette smoke. Much of natural beta-carotene is in the all trans molecule form—the same as synthetic beta-carotene. Moreover, much of the 9-cis molecule found only in natural beta-carotene is converted to the synthetic molecule before it reaches the bloodstream. Also, absorption of 9-cis beta-carotene appears to be poor, though some researchers question this finding. Despite the overlap between natural and synthetic forms, natural beta-carotene may possibly have activity that is distinct from the synthetic form. For example, studies in both animals and humans have shown that the natural form has antioxidant activity that the synthetic form lacks. Also, in one trial, pre-cancerous changes in people reverted to normal tissue with natural beta-carotene supplements, but not with synthetic supplements. Israeli researchers have investigated whether the special antioxidant effects of natural beta-carotene might help people suffering from asthma attacks triggered by exercise. People with asthma triggered by exercise were given 64 mg per day of natural beta-carotene for one week. In that report, 20 of 38 patients receiving natural beta-carotene were protected against exercise-induced asthma. However, because synthetic beta-carotene was not tested, the difference between the activity of the two supplements cannot be deduced from this report. Increasingly, doctors are recommending that people supplement only with natural beta-carotene. However, no studies have explored whether the adverse effect of synthetic beta-carotene in cigarette smokers would also occur with natural beta-carotene supplementation. Until more is known, smokers should avoid all beta-carotene supplements and others should avoid synthetic beta-carotene. In supplements, the natural form can be identified by the phrases “from D. salina,”“from an algal source,”“from a palm source,” or as “natural beta-carotene” on the label. The synthetic form is identified as “beta-carotene.” How much is usually taken? The most common beta-carotene supplement intake is probably 25,000 IU (15 mg) per day, though some people take as much as 100,000 IU (60 mg) per day. Whether the average person would benefit from supplementation with beta-carotene remains unclear. Are there any side effects or interactions? Beta-carotene supplementation, even in very large amounts, is not known to cause any serious side effects, however, excessive intake (more than 100,000 IU, or 60 mg per day) sometimes gives the skin a yellow-orange hue. People taking beta-carotene for long periods of time should also supplement with vitamin E, as beta-carotene may reduce vitamin E levels. Beta carotene supplementation may also decrease blood levels of lutein, another carotenoid. As noted above, synthetic beta-carotene has now been linked to increased risk of lung cancer in smokers. Pre-cancerous changes to lungs have appeared in animals given synthetic beta-carotene supplements, particularly those exposed to tobacco smoke. Though some research suggests that differences between synthetic and natural supplements may exist, conclusive proof of such a difference has not yet been shown. Preliminary studies in animals indicate that beta-carotene supplementation, when combined with heavy alcohol consumption, may enhance liver toxicity. Until more is known, alcoholics and persons who consume alcohol on a daily basis should avoid supplementing with beta-carotene. One study showed a slightly increased risk of vascular surgery among people with intermittent claudication who took beta-carotene supplements. Until more is known, persons wishing to use beta-carotene supplements should first consult with their doctor. Are there any drug interactions? Certain medications may interact with beta-carotene.
What does it do? Lutein is an antioxidant in the carotenoid family (a group of naturally occurring fat-soluble pigments found in plants). Lutein is the primary carotenoid present in the central area of the retina called the macula. Lutein may act as a filter to protect the macula from potentially damaging forms of light. Consequently, lutein appears to be associated with protection from age-related macular degeneration (the leading cause of blindness in older adults). Where is it found? Spinach, kale, collard greens, romaine lettuce, leeks, peas, and egg yolks are good sources of lutein. Who is likely to be deficient? While a deficiency has not been identified, people who eat more lutein-containing foods appear to be at lower risk of macular degeneration. One study found that adults with the highest dietary intake of lutein had a 57% decreased risk of macular degeneration compared with those people with the lowest intake, and of the carotenoids, lutein and zeaxanthin are most strongly associated with this protection. In a preliminary study, a similar link was suggested between low dietary lutein and increased risk of cataracts. How much is usually taken? People showing protection from macular degeneration have been reported to have eaten about 6 mg of lutein per day from food. Lutein, in supplemental form, should be taken with fat-containing food to improve absorption. Are there any side effects or interactions? No adverse effects from lutein have been reported. Lutein functions together with zeaxanthin, another antioxidant found in the same foods and supplements as lutein. At the time of writing, there were no well-known drug interactions with lutein.
What does it do? Lycopene, found primarily in tomatoes, is a member of the carotenoid family—which includes beta-carotene and similar compounds found naturally in food—and has potent antioxidant capabilities. A study conducted by Harvard researchers examined the relationship between carotenoids and the risk of prostate cancer. Of the carotenoids studied, only lycopene was clearly linked to protection. The men who had the greatest amounts of lycopene in their diet (6.5 mg per day or more) showed a 21% decreased risk of prostate cancer compared with those eating the least. This report suggests that lycopene may be an important tool in the prevention of prostate cancer. This study also reported that those who ate more than ten servings per week of tomato-based foods had a 35% decreased risk of prostate cancer compared with those eating less than 1.5 weekly servings. When the researchers looked at only advanced prostate cancer, the high lycopene eaters had an 86% decreased risk (although this did not reach statistical significance due to the small number of cases). Contrary to popular opinion, research suggests that there is no preferential concentration of lycopene in prostate tissue. Although prostate cancer patients have been reported to have low levels of lycopene in the blood, and lycopene appears to be a potent inhibitor of human cancer cells in test-tubes, evidence is conflicting concerning whether an increased intake of tomato products is protective against prostate cancer. Some studies, like the one discussed above, have reported that high consumption of tomatoes and tomato products reduces risk of prostate cancer. Other studies, however, are inconclusive, and some have found no protective association. There is some evidence that lycopene may be helpful in the treatment of prostate cancer. In a preliminary trial, 26 men with prostate cancer were randomly assigned to receive lycopene (15 mg twice a day) or no lycopene for three weeks before undergoing prostate surgery. Prostate tissue was then obtained during surgery and examined. Compared with the unsupplemented men, those receiving lycopene were found to have significantly less aggressive growth of cancer cells. In addition, a case report has been published of a 62-year-old man with advanced prostate cancer who experienced a regression of his tumor after starting 10 mg of lycopene per day and 300 mg of saw palmetto three times per day. As saw palmetto has not been previously associated with improvements in prostate cancer, the authors of the report attributed the response to the lycopene. Long-term controlled studies are needed to confirm these promising initial reports. There is no evidence that tomato intake has any effect on benign prostatic hyperplasia (BPH). Another study found that for the 25% of people with the greatest tomato intake, the risk for cancers of the gastrointestinal tract was 30–60% lower, compared with those who ate fewer tomatoes. These reduced risks were statistically significant. A study of women found that the 75% who ate the least amount of tomatoes had between 3.5 and 4.7 times the risk for cervical intraepithelial neoplasia—pre-cancerous changes of the cervix. Other researchers have also reported evidence suggesting that high dietary lycopene may be linked to protection from cervical dysplasia. While preliminary evidence also links dietary lycopene with protection from breast cancer, another study did not find this link. In a review of 72 studies, one researcher reported 57 associations between tomato intake or blood lycopene levels and decreased risk of cancer. Of these associations, 35 were statistically significant. The benefit was strongest for prostate, lung, and stomach cancers, although protective associations were also found for cancers of the pancreas, colon, rectum, esophagus, oral cavity, breast, and cervix. Because the data were from observational studies, a cause-and-effect relationship cannot be firmly established. However, the consistently lower risk of cancer associated with higher consumption of lycopene-containing tomatoes, provides a strong foundation for further research on lycopene. In Europe, researchers have found a statistically significant association between high dietary lycopene and a 48% lower risk of heart disease. Lycopene supplementation has also boosted immune function in the elderly. In that trial, 15 mg of lycopene per day increased natural killer cell activity by 28% in 12 weeks. Where is it found? Tomatoes and tomato-containing foods are high in lycopene. In the Harvard study, the only tomato-based food that did not correlate with protection was tomato juice. In an unblinded, controlled trial, lycopene supplementation, but not tomato juice, effectively increased the body’s lycopene stores. These studies suggest that the lycopene present in tomato juice is poorly absorbed. However, other research indicates that significant amounts of lycopene from tomato juice can, in fact, be absorbed. Other foods that contain lycopene include watermelon, pink grapefruit, and guava. Who is likely to be deficient? This is unknown, but people who do not eat diets high in tomatoes or tomato products are likely to consume less than optimal amounts. How much is usually taken? The ideal intake of lycopene is currently unknown; however, the men in the Harvard study with the greatest protection against cancer consumed at least 6.5 mg per day. Are there any side effects or interactions? No adverse effects have been reported with the use of lycopene. At the time of writing, there were no well-known drug interactions with lycopene.
What does it do? Vitamin B2 is needed to process amino acids and fats, activate vitamin B6 and folic acid, and help convert carbohydrates into the fuel the body runs on, ATP. Under some conditions, vitamin B2 can act as an antioxidant. Where is it found? Dairy products, eggs, and meat contain significant amounts of vitamin B2. Leafy green vegetables, whole grains, and enriched grains contain some vitamin B2. Who is likely to be deficient? Vitamin B2 deficiency can occur in alcoholics. Also, a deficiency may be more likely in people with cataracts or sickle cell anemia. In developing countries, vitamin B2 deficiency has been found to be a risk factor for the development of preeclampsia in pregnant women. People with chronic fatigue syndrome may be deficient in vitamin B2. How much is usually taken? The ideal level of intake is not known. The amounts found in many multivitamin supplements (20–25 mg) are more than adequate for most people. Are there any side effects or interactions? At supplemental and dietary levels, vitamin B2 is nontoxic. Vitamin B2 works with vitamin B1, vitamin B3, and vitamin B6. For that reason, vitamin B2 is often taken as part of a B-complex supplement. Are there any drug interactions? Certain medications may interact with vitamin B2.
What does it do? Coenzyme Q10 (CoQ10) is a powerful antioxidant that protects the body from free radicals1 and helps preserve vitamin E, the major antioxidant of cell membranes and blood cholesterol. CoQ10 is also called ubiquinone, a name that signifies its ubiquitous (widespread) distribution in the human body. CoQ10 is used by the body to transform food into the energy on which the body runs, ATP. CoQ10 supplementation has been investigated as a way to improve physical endurance because of its effect on energy production. However, most research shows that CoQ10 does not improve athletic performance. In other research, investigators reported no differences in CoQ10 in muscles or blood from patients with fibromyalgia compared to healthy people. Synthesis of sperm requires considerable energy. Due to its role in energy production, CoQ10 has been studied in infertile men. Preliminary research reports that supplementation of CoQ7, a related molecule, increased sperm counts in a group of infertile men. Healing of periodontal tissue (the gums of the mouth) may require increased energy production; therefore, researchers have explored the effects of CoQ10 supplementation in people with periodontal disease, which has been linked to CoQ10 deficiency. Double-blind research shows that people with gum disease given CoQ10 achieve better results than those given a placebo. The role of CoQ10 in energy formation also relates to how the body uses carbohydrates. Preliminary research suggests that a close relative of this nutrient lowered blood sugar levels in a group of people with diabetes. People with type 2 diabetes have been found to have significantly lower blood levels of CoQ10 compared with healthy people. Virtually every cell of the human body contains CoQ10. The mitochondria, the area of cells where energy is produced, contain the most CoQ10. The heart and liver contain the greatest amount of CoQ10. It has helped some people with congestive heart failure (CHF). —an effect reported in an analysis of eight controlled trials and found in some, though not all, double-blind studies. The beneficial effects of CoQ10 may not be seen until after several months of treatment. Discontinuation of CoQ10 supplementation in people with CHF has resulted in severe relapses and should only be attempted under the supervision of a doctor. Similar improvements have been reported in people with cardiomyopathies—a group of diseases affecting heart muscle. Research (including double-blind studies) in this area has been consistently positive. Also, due to its effect on heart muscle, researchers have studied CoQ10 in people with heart arrhythmias. Preliminary research in this area reported improvement after approximately one month in people with premature ventricular beats (a form of arrhythmia) who also suffer from diabetes. Angina patients taking 150 mg per day of CoQ10 report a greater ability to exercise without experiencing chest pain. This has been confirmed in independent investigations. CoQ10 appears to increase the heart’s tolerance to a lack of oxygen. Perhaps as a result, preliminary research has shown that problems resulting from heart surgery occurred less frequently in people given CoQ10 compared with the control group. Muscle mitochondria lack adequate CoQ10 in people with muscular dystrophy, a problem that could affect muscle function. In a double-blind three-month trial, four of eight people with muscular dystrophy had improvements in heart function and sense of well-being when supplementing CoQ10. Mitochondrial function also appears to be impaired in people with Alzheimer’s disease. Due to CoQ10’s effects on mitochondrial functioning, one group of researchers has given CoQ10 (along with iron and vitamin B6) to several people with Alzheimer’s disease and reported the progression of the disease appeared to have been prevented for one and a half, to two years. CoQ10 also modulates immunity. Perhaps as a result, a few cases have been reported in which women with metastatic breast cancer (cancer that had spread to other tissues) had a regression of their cancer after treatment with a very large amount of CoQ10 (390 mg per day). CoQ10 appears to modulate blood pressure by reducing resistance to blood flow. Several trials have reported that supplementation with CoQ10 significantly reduced blood pressure in people with hypertension, usually after ten weeks to four or more months of treatment.
In a double-blind study of 21 patients with chronic renal (kidney) failure, 15 of whom were on dialysis, supplementation with 60 mg of CoQ10 three times per day for four weeks improved certain measures of kidney function (BUN, serum creatinine, and creatinine clearance), compared with placebo, and eliminated the need for dialysis in some patients. Because chronic renal failure is a serious and complicated disease, individuals with this condition should take CoQ10 only under strict medical supervision. Where is it found? CoQ10 is found primarily in fish and meat, but the amounts in food are far less than what can be obtained from supplements. Who is likely to be deficient? Deficiency is poorly understood, but it may be caused by synthesis problems in the body rather than an insufficiency in the diet. Low blood levels have been reported in people with heart failure, cardiomyopathy, gingivitis (inflammation of the gums), morbid obesity, hypertension, muscular dystrophy, diabetes, AIDS, and in some people on kidney dialysis. People with phenylketonuria (PKU) may be deficient in CoQ10 because of dietary restrictions. CoQ10 levels are also generally lower in older people. The test used to assess CoQ10 status is not routinely available from medical laboratories. Which form of coenzyme Q10 is best? Some, but not all, research suggests that a fat-soluble form of CoQ10 is absorbed better than CoQ10 in granular (powder) form. How much is usually taken? Adult levels of supplementation are usually 30–90 mg per day, although people with specific health conditions may supplement with higher levels (with the involvement of a physician). Most of the research on heart conditions has used 90–150 mg of CoQ10 per day. People with cancer who consider taking much higher amounts should discuss this issue with a doctor before supplementing. There are several anecdotal reports of large amounts of CoQ10 resulting in improvements in certain types of cancer. However, controlled trials are needed to confirm these preliminary observations. Most doctors recommend that CoQ10 be taken with meals to improve absorption. Are there any side effects or interactions? Congestive heart failure patients who are taking CoQ10 should not discontinue taking CoQ10 supplements unless under the supervision of a doctor.
An isolated test tube study reported that the anticancer effect of a certain cholesterol-lowering drug was blocked by addition of CoQ10. So far, experts in the field have put little stock in this report because its results have not yet been confirmed in animal, human, or even other test tube studies. The drug used in the test tube is not used to treat cancer, and preliminary information regarding the use of high amounts of CoQ10 in humans suggests the possibility of anticancer activity. Are there any drug interactions? Certain medications may interact with coenzyme Q10.
What does it do? Cysteine is a nonessential amino acid (protein building block), meaning that cysteine can be made in the human body.
Cysteine is one of the few amino acids that contains sulfur. This allows cysteine to bond in a special way and maintain the structure of proteins in the body. Cysteine is a component of the antioxidant, glutathione. The body also uses cysteine to produce taurine, another amino acid. Cysteine can also be converted into glucose and used as a source of energy. Cysteine strengthens the protective lining of the stomach and intestines, which may help prevent damage caused by aspirin and similar drugs. In addition, cysteine may play an important role in the communication between immune system cells. Cysteine is rarely used as a dietary supplement. N-acetyl cysteine (NAC), which contains cysteine, is more commonly used as a supplement. Where is it found? The body can synthesize cysteine from methionine and other building blocks. Cysteine, the amino acid from which NAC is derived, is found in most high-protein foods. Who is likely to be deficient? According to several studies, blood levels of cysteine and glutathione are low in people infected with HIV. Cysteine has a role in the proper function of the immune system, so a deficiency of this amino acid may either contribute to, or result from, immune suppression associated with HIV. How much is usually taken? Most people do not need to supplement with cysteine. Almost nothing is known about appropriate supplemental levels, in part because almost all clinical research has been done with N-acetyl cysteine and not cysteine itself. Are there any side effects or interactions? No consistent adverse effects of NAC have been reported in humans. One small study found that daily amounts of 1.2 grams or more could lead to oxidative damage. Extremely large amounts of cysteine, the amino acid NAC is derived from, may be toxic to nerve cells in rats. Adequate amounts of methionine are needed in the diet, as the precursor to cysteine, to prevent cysteine deficiency. At the time of writing, there were no well-known drug interactions with cysteine.
Parts used and where grown: A close relative of American blueberry, bilberry grows in northern Europe, Canada, and the United States. The ripe berries are primarily used in modern herbal extracts. Historical or traditional use (may or may not be supported by scientific studies): The dried berries and leaves of bilberry have been recommended for a wide variety of conditions, including scurvy, urinary tract infections, kidney stones, and diabetes. Perhaps the most sound historical application is the use of the dried berries to treat diarrhea. Modern research of bilberry was partly based on its use by British World War II pilots, who noticed that their night vision improved when they ate bilberry jam prior to night bombing raids. Active constituents: Anthocyanosides, the flavonoid complex in bilberries, speed the regeneration of rhodopsin, the purple pigment that is used by the rods in the eye for night vision. While earlier trials suggested that taking bilberry could benefit people with night blindness, more recent trials with healthy volunteers have found no effect of bilberry on night vision. Preliminary human trials conducted in Europe show that bilberry may prevent cataracts, and may even help to treat people with mild retinopathies (such as macular degeneration and diabetic retinopathy). Anthocyanosides are potent antioxidants. They support normal formation of connective tissue and strengthen capillaries in the body. Anthocyanosides may also improve capillary and venous blood flow. Bilberry may also prevent blood vessel thickening due to diabetes. Bilberry protects cholesterol from oxidizing in test tubes. While this action is thought to help prevent atherosclerosis, no human trials have studied whether bilberry may be useful in the regard. How much is usually taken? Bilberry herbal extract in capsules or tablets standardized to provide 25% anthocyanosides are typically recommended at 240–600 mg per day. Herbalists have traditionally recommended taking 1–2 ml two times per day in tincture form, or 20–60 grams of the fruit daily. Are there any side effects or interactions? In recommended amounts, no side effects have been reported with bilberry extract. At the time of writing, there were no well-known drug interactions with bilberry.
Parts used and where grown: The vast majority of turmeric comes from India. Turmeric is one of the key ingredients in many curries, giving them color and flavor. The root and rhizome (underground stem) are used medicinally. Historical or traditional use (may or may not be supported by scientific studies): In Ayurvedic medicine, turmeric was prescribed for treatment of many conditions, including poor vision, rheumatic pains, and coughs, and to increase milk production. Native peoples of the Pacific sprinkled the dust on their shoulders during ceremonial dances and used it for numerous medical problems ranging from constipation to skin diseases. Turmeric was used for numerous intestinal infections and ailments in Southeast Asia. Active constituents: The active constituent is known as curcumin. It has been shown to have a wide range of therapeutic actions. First, it protects against free radical damage because it is a strong antioxidant. Second, it reduces inflammation by lowering histamine levels and possibly by increasing production of natural cortisone by the adrenal glands. Third, it protects the liver from a number of toxic compounds. Fourth, it has been shown to reduce platelets from clumping together, which in turn improves circulation and may help protect against atherosclerosis. There are also test-tube and animal studies showing a cancer-preventing action of curcumin. In one of these studies, curcumin effectively inhibited metastasis (uncontrolled spread) of melanoma (skin cancer) cells. This may be due to its antioxidant activity in the body. Curcumin inhibits HIV in test tubes, though human trials are needed to determine if it has any usefulness for treating humans with this condition. A preliminary trial in people with rheumatoid arthritis found curcumin to be somewhat useful for reducing inflammation and symptoms such as pain and stiffness. A separate double-blind trial found that curcumin was superior to placebo or phenylbutazone (an NSAID) for alleviating post-surgical inflammation. While a double-blind trial has found turmeric helpful for people with indigestion, results in people with stomach or intestinal ulcers have not shown it to be superior to a placebo and have demonstrated it to be less effective than antacids. Preliminary research indicates a possible benefit of oral curcumin supplementation (375 mg of turmeric extract with 95% curcuminoids three times daily for 12 weeks) for chronic anterior uveitis (inflammation of the iris and middle coat of the eyeball). How much is usually taken? Turmeric extracts standardized at 90 to 95% curcumin can be taken in the amount of 250 to 500 mg three times per day. Tincture, 0.5–1.5 ml three times per day, is sometimes recommended. Are there any side effects or interactions? Used in the recommended amounts, turmeric is generally safe. It has been used in large quantities as a condiment with no adverse reactions. Some herbal books recommend not taking high amounts of turmeric during pregnancy as it may cause uterine contractions and people with gallstones or obstruction of bile passages should consult their healthcare practitioner before using turmeric. At the time of writing, there were no well-known drug interactions with turmeric. Proanthocyanidins: Also indexed as: Grape Seed Extract, Oligomeric Proanthocyanidins (OPCs), Procyanidolic Oligomers (PCOs) What do they do? Proanthocyanidins—also called “OPCs” for oligomeric procyanidins or “PCOs” for procyanidolic oligomers—are a class of nutrients belonging to the flavonoid family. Proanthocyanidins have antioxidant activity and they play a role in the stabilization of collagen and maintenance of elastin—two critical proteins in connective tissue that support organs, joints, blood vessels, and muscle. Possibly because of their effects on blood vessels, proanthocyanidins have been reported in double-blind research to reduce the duration of edema after face-lift surgery from 15.8 to 11.4 days. In very preliminary research, proanthocyanidins were reported to have anti-mutagenic activity (i.e., to prevent chromosomal mutations). Proanthocyanidins have been shown to strengthen capillaries in double-blind research using as little as 100 mg per day. In another double-blind trial, French researchers reported that women with chronic venous insufficiency had reduced symptoms using 150 mg per day. In another French double-blind trial, supplementation with 100 mg taken three times per day, resulted in benefits within four weeks. Proanthocyanidins (200 mg per day for five weeks) have improved aspects of vision (visual performance in the dark and after exposure to glare) in healthy people. A product that is high in proanthocyanidins has been shown to prevent and reverse abnormal blood clotting in smokers. Where are they found? Proanthocyanidins can be found in many plants, most notably pine bark, grape seed, and grape skin. However, bilberry, cranberry, black currant, green tea, black tea, and other plants also contain these flavonoids. Nutritional supplements containing proanthocyanidins extracts from various plant sources are available, alone or in combination with other nutrients, in herbal extracts, capsules, and tablets. Who is likely to be deficient? Flavonoids and proanthocyanidins are not classified as essential nutrients because their absence does not induce a deficiency state. However, proanthocyanidins may have many health benefits, and anyone not eating the various plants that contain them would not derive these benefits. How much is usually taken? Flavonoids (proanthocyanidins and others) are a significant source of antioxidants in the average diet. Proanthocyanidins at 50–100 mg per day is considered a reasonable supplemental level by some doctors, but optimal levels remain unknown. Are there any side effects or interactions? Flavonoids, in general, and proanthocyanidins, specifically, have not been associated with any consistent side effects. As they are water-soluble nutrients, excess intake is simply excreted in the urine. At the time of writing, there were no well-known drug interactions with Proanthocyanidins.
Parts used and where grown: Ginkgo biloba is the world’s oldest living species of tree. Individual trees live as long as 1,000 years. Ginkgo grows most predominantly in the southern and eastern United States, southern France, China, and Korea. The leaves of the tree are used in modern herbal medicine. Historical or traditional use (may or may not be supported by scientific studies): Medicinal use of ginkgo can be traced back almost 5,000 years in Chinese herbal medicine. The nuts of the tree were most commonly recommended and used to treat respiratory tract ailments. The use of the leaves is a modern development originating in Europe. Active constituents: The medical benefits of Ginkgo biloba extract (GBE) are attributed primarily to two groups of active constituents: the ginkgo flavone glycosides and the terpene lactones. Ginkgo flavone glycosides, which typically make up approximately 24% of the extract, are primarily responsible for GBE’s antioxidant activity and may mildly inhibit platelet aggregation (stickiness). These two actions may help GBE prevent circulatory diseases, such as atherosclerosis, and support the brain and central nervous system. In addition to the cardiovascular system, GBE’s antioxidant action may also extend to the brain and retina of the eye. Preliminary trials have suggested potential benefit for people with macular degeneration and diabetic retinopathy. The terpene lactones found in GBE, known as ginkgolides and bilobalide, typically make up approximately 6% of the extract. They are associated with increasing circulation to the brain and other parts of the body and may exert a protective action on nerve cells. GBE regulates the tone and elasticity of blood vessels, making circulation more efficient. Ginkgo is also well-known for its effect on memory and thinking (cognitive function). It may enhance cognitive performance in healthy older adults, in people with age-related cognitive decline, and in people with Alzheimer’s disease. How much is usually taken? Most clinical trials have used between 120 and 240 mg of GBE (standardized to contain 6% terpene lactones and 24% flavone glycosides) per day, generally divided into two or three portions. The higher amount (240 mg per day) has been used in some people with mild-to-moderate Alzheimer’s disease, age-related cognitive decline, intermittent claudication, and resistant depression. GBE may need to be taken for eight to twelve weeks before desired actions such as cognitive improvement are noticed. Although nonstandardized Ginkgo biloba leaf and tinctures are available, there is no well-established amount or use for these forms. Are there any side effects or interactions? Excessive bleeding has been reported in a few individuals taking GBE, although a cause/effect relationship was not proven. In addition, two elderly individuals with well-controlled epilepsy developed recurrent seizures within two weeks after starting GBE. Mild headaches lasting for a day or two and mild upset stomach have been reported in a small number of people using GBE. Ginkgo leaves are known to contain a group of potentially toxic constituents known as alkylphenols. The ginkgo extracts known as EGb 761 and LI 1370 have been shown to conform to the safety limits for these constituents (less that 5 ppm), as set forth by the German Commission E. Other forms of ginkgo may contain higher concentrations of alkylphenols. One small clinical trial found that ginkgo supplementation for three months increased secretion of insulin by the pancreas, but did not affect blood glucose levels, in healthy young adults. These results suggest that the participants may have developed an insensitivity to insulin, a potential concern because insulin insensitivity may be a precursor to type 2 diabetes. However, this trial does not prove that ginkgo causes insulin insensitivity, nor does it prove that long-term ginkgo supplementation increases the risk for any disease. In addition, the results of this trial are not consistent with other research on ginkgo. Larger and more rigorously designed clinical trials of ginkgo supplementation have found no significant adverse effects after as many as 12 months of supplementation. People should seek an accurate medical diagnosis prior to self-prescribing GBE. This is especially important for the elderly, whose circulatory conditions can involve serious disease, and for people scheduled for surgery, as GBE may affect bleeding time. Are there any drug interactions? Certain medications may interact with Ginkgo biloba .
cancer prevention and diet Cancer is the second leading cause of death in Americans. Cancer refers to a large number of diseases categorized by unregulated replication of cells.
The contents of this article are limited to information about diet and to a discussion of cancer prevention—not treatment. Prevention of cancer in a person who has never had cancer is called “primary” prevention. Primary prevention is the focus of this article.
This article includes a discussion of studies that have assessed whether certain dietary ingredients may be beneficial in connection with the reduction of risk of developing cancer.
However, this information is provided solely to aid consumers in discussing such issues with their health care providers. It is not advised nor is this information intended to advocate, promote, or encourage self-use of this information for cancer risk reduction.
Finally, some of the studies suggest an association between high blood or dietary levels of a particular dietary ingredient with a reduced risk of developing cancer. Even if such an association were established, this does not mean that dietary supplements containing large amounts of the dietary ingredient will necessarily have a cancer risk reduction effect.
Prevention of a recurrence in a cancer patient who is in remission is called “secondary” prevention. Whether the information in this article would be helpful to people interested in secondary prevention is, for the most part, unknown. However, of cancer patients who are in complete remission, the information presented here is unlikely to help people who were ever diagnosed with metastatic cancer (also known as stage IV, or advanced, cancer).
Information on the prevention of breast, colon, lung, and prostate cancers is not provided in this article. To find out more about these specific forms of cancer, read the articles on Breast Cancer, Colon Cancer, Lung Cancer, and Prostate Cancer.
Dietary changes that may be helpful: The following dietary changes have been studied in connection with cancer.
Alcohol and Cancer
Alcohol consumption significantly increases the risk of cancers of the mouth (oral/oropharyngeal cancer), throat (esophageal cancer), and voice box (laryngeal cancer), particularly in conjunction with cigarette smoking.1 2 3 Most studies documenting these associations also report that former drinkers have significantly lower risks for these cancers compared with current drinkers. Strong correlations between alcohol consumption and the risk of having liver cancer have also been reported.4 5
Little is known about the effect of alcohol intake on the risk of female cancers other than breast cancer. Of the few published studies, findings have been inconsistent.6 7 8 9
Fiber
Whole grains (such as rye, brown rice, and whole wheat) contain high amounts of insoluble fiber—the type of fiber some scientists believe may help protect against a variety of cancers. In an analysis of the data from many studies, people who eat relatively high amounts of whole grains were reported to have low risks of lymphomas and cancers of the pancreas, stomach, colon, rectum, breast, uterus, mouth, throat, liver, and thyroid.10 Most research focusing on the relationship between cancer and fiber has focused on breast and colon cancers.
Consuming a diet high in insoluble fiber is best achieved by switching from white rice to brown rice and from bakery goods made with white flour or mixed flours to 100% whole wheat bread, whole rye crackers, and whole grain pancake mixes. Refined white flour is generally listed on food packaging labels as “flour,”“enriched flour,”“unbleached flour,”“durum wheat,”“semolina,” or “white flour.” Breads containing only whole wheat are often labeled “100% whole wheat.”
Vegetarianism
The following two possibilities are both strongly supported by research findings:
· Some foods consumed by vegetarians may protect against cancer.
· Eating meat may increase the risk of cancer.
Compared with meat eaters, most,11 but not all,12 studies have found that vegetarians are less likely to be diagnosed with cancer. Vegetarians have also been shown to have stronger immune function, possibly explaining why vegetarians may be partially protected against cancer.13 Female vegetarians have been reported to have lower estrogen levels compared with meat-eating women, possibly explaining a lower incidence of uterine and breast cancers.14 A reduced risk for various cancers is only partly,15 not totally,16 explained by differences in body weight, smoking habits, and other lifestyle issues.
Fruits and Vegetables
Consumption of fruits and vegetables is widely accepted as lowering the risk of most common cancers.17 Many doctors recommend that people wishing to reduce their risk of cancer eat several pieces of fruit and several portions of vegetables every day. Optimal intakes remain unknown.
Most doctors also recommend that people should not consider supplements as substitutes for the real thing. Some of the anticancer substances found in produce have probably not yet been discovered, while others are not yet available in supplement form. More important, some research, particularly regarding synthetic beta-carotene, does not support the idea that taking supplements has the same protective value against cancer as does consumption of fruits and vegetables.
Flavonoids
Flavonoids are found in virtually all herbs and plant foods. Consumption of flavonoid-rich onions and apples contain large amounts of one flavonoid called quercetin. Consumption of flavonoids in general, or quercetin-containing foods in particular,18 has been associated with protection against cancer in some,19 but not all,20 preliminary studies.
Tomatoes
Tomatoes contain lycopene—an antioxidant similar in structure to beta-carotene. Most lycopene in our diet comes from tomatoes, though traces of lycopene exist in other foods. Lycopene inhibits the proliferation of cancer cells in test tube research.21
A review of published research found that higher intake of tomatoes or higher blood levels of lycopene correlated with protection from cancer in 57 of 72 studies. Findings in 35 of these studies were statistically significant.22 Evidence of a protective effect for tomato consumption was strongest for cancers of the prostate, lung, and stomach, but some evidence of a protective effect also appeared for cancers of the pancreas, colon, rectum, esophagus (throat), mouth, breast, and cervix.
Cruciferous vegetables
Cabbage, Brussels sprouts, broccoli, and cauliflower belong to the Brassica family of vegetables, also known as “cruciferous” vegetables. In test tube and animal studies, these foods have been associated with anticancer activity,23 possibly due to several substances found in these foods, such as indole-3-carbinol,24 glucaric acid (calcium D-glucarate),25 and sulforaphane.26 In a preliminary human study, people who ate cruciferous vegetables were reported to have a lower-than-average risk for bladder cancer.27
Meat (how it is cooked) and childhood cancers
In one report, high consumption of hot dogs was associated with an almost tenfold increase in the risk of childhood leukemia when compared with low consumption.28 In another report, maternal consumption of hot dogs and childhood consumption of hamburgers or hot dogs at least once per week were associated with a doubling of the risk of cancers in children.29 A review of nine studies found an association between consumption by pregnant women of cured meat and the risk of brain cancer in their offspring.30 These associations do not yet constitute proof that eating hot dogs or hamburgers causes cancer in children, and evidence linking cured meat consumption to childhood cancers remains somewhat inconsistent.31
In the report studying the effects of eating hot dogs and hamburgers, the association between meat eating and leukemia was weakest among children who took vitamin supplements. Processed meats, such as hot dogs, contain nitrates and nitrites—precursors to carcinogens. Antioxidants found in multivitamins keep nitrates and nitrites from converting into those carcinogens. Therefore, the association between vitamin consumption in children and protection against childhood cancers remains plausible, though unproven.
Fish
Fish eaters have been reported to have low risks of cancers of the mouth, throat, stomach, colon, rectum, pancreas,32 lung,33 breast,34 and prostate.35 The omega-3 fatty acids found in fish are thought by some researchers to be the components of fish responsible for protection against cancer.36
Coffee
Years ago, researchers reported the greater the consumption of coffee in a country, the higher the risk of pancreatic cancer in that country.37 An analysis of data from studies published between 1981 and 1993 did find some association between high consumption of coffee and an increased risk of pancreatic cancer.38 Surprisingly, however, the same report found that people drinking only one or two cups of coffee per day had, on average, a lower risk of pancreatic cancer compared with people who never drink coffee.
Most,39 40 41 but not all,42 published reports have shown coffee drinkers are at increased risk of bladder cancer, though in one case the relationship was found only in men.43 In another study, the association was found only with caffeinated coffee.44 A review of 35 trials found a small (7%) increased risk of bladder cancer in coffee drinkers compared with people not drinking coffee—a difference not statistically significant.45
Calories
Scientists have known for many years that severe restriction of calories dramatically reduces the risk of cancer in laboratory animals.46 Scientists speculate that caloric content of the human diet may also affect cancer rates,47 though much less is known about the effect, if any, of moderate caloric restrictions in humans. In one report, adults with cancer were more likely to have consumed more calories during childhood compared with healthy adults.48 In other reports, attempts to find associations between reduced intake of calories and cancer have produced mixed results.49 50 51
Only severe restriction in caloric intake provides significant protection in animal studies. As most people are unlikely to severely restrict calories, the association between caloric restriction and protection from cancer may ultimately prove to only be of academic interest.
Dietary Fat
In studying data from country to country, incidence of ovarian cancer correlates with dietary fat intake.52 According to preliminary research, consumption of saturated fat, dietary cholesterol (as found in eggs),53 and animal fat in general54 correlates with the risk of ovarian cancer.
Preliminary studies suggest dietary fat may correlate with the risk of uterine cancer.55 Some of the excess risk appears to result from increased body weight that results from a high-fat diet.56
Many years ago, researchers reported that animals on a high-fat diet formed skin cancers more rapidly than did other animals.57 Although some preliminary human research has found no relationship between dietary fat intake and the risk of skin cancer,58 patients with basal cell and squamous cell skin cancers who were put on a low-fat diet for two years were reported to show a significant decrease in the number of new skin cancers compared with patients who maintained a high-fat diet.59 Similarly, precancerous lesions of the skin have been prevented in people put on a low-fat diet.60
Polyunsaturated Fats
A chain of carbon atoms in which several are not attached to the maximum possible amount of hydrogen is called “polyunsaturated”––in other words, unsaturated with hydrogen in several places. When nutrition researchers talk about polyunsaturated fatty acids, they are often referring primarily to linoleic acid—a fatty acid found in nuts and seeds and most vegetable oils.
In animal research, the consumption of polyunsaturated fatty acids increases the risk of some cancers.61 However, in humans, most,62 63 64 though not all,65 reports do not find an association between polyunsaturates and cancer risks.
Sugar
A preliminary study has reported an association between an increasing intake of sugar or sugar-containing foods and an increased risk of gallbladder cancer.66 Whether this association exists because sugar directly promotes cancer or because sugar consumption is only a marker for some other dietary or lifestyle factor remains unknown.
Salt
In preliminary research, increasing intake of salt correlates with increased risk of stomach cancer.67 68 Associations between foods preserved with salt and the risk of cancers of the head and neck have also been reported.69
Atherosclerosis, or hardening of the arteries, is a very common disease of the major blood vessels. It is characterized by fatty streaks along the vessel walls and by deposits of cholesterol and calcium. Atherosclerosis of arteries supplying the heart is called coronary artery disease. It can restrict the flow of blood to the heart, which often triggers heart attacks—the leading cause of death in Americans and Europeans. Atherosclerosis of the arteries supplying the legs causes a condition called intermittent claudication.
People with elevated cholesterol levels are much more likely to have atherosclerosis than people with low cholesterol levels. Many important nutritional approaches to protecting against atherosclerosis are aimed at lowering serum cholesterol levels. People with diabetes are also at very high risk for atherosclerosis, as are people with elevated triglycerides and high homocysteine. What are the symptoms of atherosclerosis? Atherosclerosis is typically a silent disease until one of the many late-stage vascular manifestations intervenes. Some people with atherosclerosis may experience angina (chest pain) or intermittent claudication (leg cramps and pain) on exertion. Symptoms such as these develop gradually as the disease progresses. How is it treated? Prevention is the highest form of treatment for atherosclerosis. Once the disease is established, treatment is directed at the various complications (i.e., angina, heart attacks, heart failure, stroke, kidney failure, and peripheral vascular disease). Dietary changes that may be helpful: The most important dietary changes in protecting arteries from atherosclerosis include avoiding meat and dairy fat and avoiding foods that contain trans fatty acids (margarine, some vegetable oils, and many processed foods containing vegetable oils). Increasingly, the importance of avoiding trans fatty acids is being accepted by the scientific community. Leading researchers have recently begun to view the evidence linking trans fatty acids to markers for heart disease as “unequivocal.” People who eat diets high in alpha-linolenic acid (ALA), which is found in canola and flaxseed oils, have higher blood levels of omega-3 fatty acids than those consuming lower amounts, which may confer some protection against atherosclerosis. In 1994, researchers conducted a study in people with a history of heart disease, using what they called the “Mediterranean” diet. The diet differed significantly from what people from Mediterranean countries actually eat, in that it contained little olive oil. Instead, the diet included a special margarine high in ALA. Those people assigned to the Mediterranean diet had a remarkable 70% reduced risk of dying from heart disease compared with the control group during the first 27 months. Similar results were also confirmed after almost four years. The diet was high in beans and peas, fish, fruit, vegetables, bread, and cereals, and low in meat, dairy fat, and eggs. Although the authors believe that the high ALA content of the diet was partly responsible for the surprising outcome, other aspects of the diet may have been partly or even totally responsible for decreased death rates. Therefore, the success of the Mediterranean diet does not prove that ALA protects against heart disease. A systematic review of 20 years of research evaluated the association between dietary fiber and coronary heart disease. The meta-analysis portion of this review showed that regular whole grain foods are associated with a coronary heart disease risk reduction of about 26%. In general, the fibers most linked to the reduction of cholesterol levels are found in oats, psyllium seeds, fruit (pectin) and beans (guar gum). An analysis of many soluble fiber trials proves that a cholesterol lowering effect exists, but the amount the cholesterol falls is quite modest. For unknown reasons, however, diets higher in insoluble fiber (found in whole grains and vegetables and mostly unrelated to cholesterol levels) have been reported to correlate better with protection against heart disease in both men and women. Some trials have used 20 grams of additional fiber per day for several months to successfully lower cholesterol. Independent of their action on serum cholesterol, foods that contain high amounts of cholesterol—mostly egg yolks—can induce atherosclerosis. It makes sense to reduce the intake of egg yolks. However, eating eggs does not increase serum cholesterol as much as eating saturated fat, and eggs may not increase serum cholesterol at all if the overall diet is low in fat. A decrease in atherosclerosis resulting from a pure vegetarian diet (no meat, poultry, dairy or eggs), combined with exercise and stress reduction, has been proven by controlled medical research. Preliminary evidence has suggested that excessive salt consumption is a risk factor for heart disease and death from heart disease in overweight people. Controlled trials are needed to confirm these observations. Eating a diet high in refined carbohydrates (e.g., white flour, white rice, simple sugars) appears to increase the risk of coronary heart disease, and thus of heart attacks, especially in overweight women. However, controlled trials of reducing refined carbohydrate intake to prevent heart disease have not been attempted to confirm these preliminary findings. Lifestyle changes that may be helpful: Virtually all doctors acknowledge the abundant evidence that smoking is directly linked to atherosclerosis and heart disease. Quitting smoking protects many people from atherosclerosis and heart disease, and is a critical step in the process of disease prevention. Obesity, type A behavior (time conscious, impatient, and aggressive), stress, and sedentary lifestyle are all associated with an increased risk of atherosclerosis; interventions designed to change these risk factors are linked to protection from this condition. Aggressive verbal or physical responses when angry have been consistently related to coronary atherosclerosis in numerous preliminary studies. A low level of social support, especially when combined with a high level of outwardly expressed anger has also been associated with accelerated progression of coronary atherosclerosis. Nutritional supplements that may be helpful: Tocotrienols may offer protection against atherosclerosis by preventing oxidative damage to LDL cholesterol. In a double-blind trial in people with severe atherosclerosis of the carotid artery—the main artery supplying blood to the head—tocotrienol administration (200 mg per day) reduced the level of lipid peroxides in the blood. Moreover, people receiving tocotrienols for 12 months had significantly more protection against atherosclerosis progression, and in some cases reductions in the size of their atherosclerotic plaques, compared with those taking a placebo. Supplementation with fish oil, rich in omega-3 fatty acids, has been associated with favorable changes in various risk factors for atherosclerosis and heart disease in some, but not all, studies. A double-blind trial showed that people with atherosclerosis who took fish oil (6 grams per day for 3 months and then 3 grams a day for 21 months) had significant regression of atherosclerotic plaques and a decrease in cardiovascular events (e.g., heart attack and stroke) compared with those who did not take fish oil. These results contradict the findings of an earlier controlled trial in which fish oil supplementation for two years (6 grams per day) did not promote major favorable changes in the diameter of atherosclerotic coronary arteries. In some studies, people who consumed more selenium in their diet had a lower risk of heart disease. In one double-blind report, people who had already had one heart attack were given 100 mcg of selenium per day or placebo for six months. At the end of the trial, there were four deaths from heart disease in the placebo group but none in the selenium group; however, the number of people was too small for this difference to be statistically significant. Some doctors recommend that people with atherosclerosis supplement with 100–200 mcg of selenium per day. Experimentally increasing homocysteine levels in humans has led to temporary dysfunction of the cells lining blood vessels. Researchers are concerned this dysfunction may be linked to atherosclerosis and heart disease. Vitamin C has been reported in one controlled study to reverse the dysfunction caused by increases in homocysteine. Vitamin C also protects LDL. Despite the protective mechanisms attributed to vitamin C, some research has been unable to link vitamin C intake to protection against heart disease. These negative trials have mostly been conducted using people who consume 90 mg of vitamin C per day or more—a level beyond which further protection of LDL may not occur. Studies of people who eat foods containing lower amounts of vitamin C have been able to show a link between dietary vitamin C and protection from heart disease. Therefore, leading vitamin C researchers have begun to suggest that vitamin C may be important in preventing heart disease, but only up to 100–200 mg of intake per day. In a double-blind trial, supplementation with 250 mg of timed-release vitamin C twice daily for three years resulted in a 15% reduction in the progression of atherosclerosis, compared with placebo. Many doctors suggest that people take vitamin C—often 1 gram per day—despite the fact that research does not yet support levels higher than 500 mg per day. Vitamin E is an antioxidant that serves to protect LDL from oxidative damage and has been linked to prevention of heart disease in double-blind research. Many doctors recommend 400–800 IU of vitamin E per day to lower the risk of atherosclerosis and heart attacks. However, some leading researchers suggest taking only 100–200 IU per day, as studies that have explored the long-term effects of different supplemental levels suggest no further benefit beyond that amount, and research reporting positive effects with 400–800 IU per day have not investigated the effects of lower intakes. In a double-blind trial, people with high cholesterol who took 136 IU of natural vitamin E per day for three years had 10% less progression of atherosclerosis compared with those taking placebo. Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease in most research, though uncertainty remains about whether elevated homocysteine actually causes heart disease. Although some reports have found associations between homocysteine levels and dietary factors, such as coffee and protein intakes, evidence linking specific foods to homocysteine remains preliminary. Higher blood levels of vitamin B6, vitamin B12, and folic acid are associated with low levels of homocysteine and supplementing with these vitamins lowers homocysteine levels. While several trials have consistently shown that B6, B12, and folic acid lower homocysteine, the amounts used vary from study to study. Many doctors recommend 50 mg of vitamin B6, 100–300 mcg of vitamin B12, and 500–800 mcg of folic acid. Even researchers finding only inconsistent links between homocysteine and heart disease have acknowledged that a B vitamin might offer protection against heart disease independent of the homocysteine-lowering effect. In one trial, people with normal homocysteine levels had demonstrable reversal of atherosclerosis when supplementing B vitamins (2.5 mg folic acid, 25 mg vitamin B6, and 250 mcg of vitamin B12 per day). For the few cases in which vitamin B6, vitamin B12, and folic acid fail to normalize homocysteine, adding 6 grams per day of betaine (trimethylglycine) may be effective. Of these four supplements, folic acid appears to be the most important. Attempts to lower homocysteine by simply changing the diet rather than by using vitamin supplements have not been successful. Quercetin, a flavonoid, protects LDL cholesterol from damage. While several preliminary studies have found that eating foods high in quercetin lowers the risk of heart disease, the research on this subject is not always consistent, and some research finds no protective link. Quercetin is found in apples, onions, black tea, and as a supplement. In some studies, dietary amounts linked to protection from heart disease are as low as 35 mg per day. Though low levels (2 grams per day) of evening primrose oil appear to be without action, 3–4 grams per day have lowered cholesterol in double-blind research. Lowering cholesterol levels should in turn reduce the risk of atherosclerosis. Preliminary research shows that chondroitin sulfate may prevent atherosclerosis in animals and humans and may also prevent heart attacks in people who already have atherosclerosis. However, further research is needed to determine the value of chondroitin sulfate supplements for preventing or treating atherosclerosis. Preliminary studies have found that people who drink red wine, which contains resveratrol, are at lower risk of death from heart disease. Because of its antioxidant activity and its effect on platelets, some researchers believe that resveratrol is the protective agent in red wine. Resveratrol research remains very preliminary, however, and as yet there is no evidence that the amounts found in supplements help prevent atherosclerosis in humans. In 1992, a Finnish study found a strong link between unnecessary exposure to iron and increased risk for heart disease. Since then many studies have not found that link, though perhaps an equal number have been able to confirm the outcome of the original report. One 1999 analysis of 12 studies looking at iron status and heart disease found no overall relationship, though another 1999 analysis of published studies came to a different conclusion. While the effect of unnecessary exposure to iron, including iron supplements, on the risk of heart disease remains unclear, there is no benefit in supplementing iron in the absence of a diagnosed deficiency. The carotenoid, lycopene, has been found to be low in the blood of people with atherosclerosis, particularly if they are smokers. Although no association between atherosclerosis and blood level of any other carotenoid (e.g., beta-carotene) was found, the results of this study suggested a protective role for lycopene. Lycopene is present in high amounts in tomatoes. Herbs that may be helpful: Many actions associated with herbal supplements may help prevent or potentially alleviate atherosclerosis. Herbs such as garlic and ginkgo appear to directly affect the hardened arteries by multiple mechanisms. Herbs such as psyllium, guggul, and fenugreek reduce cholesterol and other lipid levels in the blood—known risk factors for hardened arteries. A related group are herbs, including green tea, prevents the oxidation of cholesterol, an important step in protecting against atherosclerosis. Finally, there are herbs such as ginger and turmeric that reduce excessive stickiness of platelets, thereby reducing atherosclerosis. Garlic has been shown to prevent atherosclerosis in a four-year double-blind trial. The preparation used, standardized for 0.6% allicin content, provided 900 mg of standardized garlic powder per day. The people in this trial were 50 to 80 years old, and the benefits were most notable in women. This trial points to the long-term benefits of garlic to both prevent and possibly slow the progression of atherosclerosis in people at risk. Garlic has also lowered cholesterol levels in double-blind research, though more recently, some double-blind trials have not found garlic to be effective. Some of the negative trials have flaws in their design. Nonetheless, the relationship between garlic and cholesterol-lowering is somewhat unclear. Garlic has also been shown to prevent excessive platelet adhesion in humans. Allicin, often considered the main active component of garlic, is not alone in this action. The constituent known as ajoene has also shown beneficial effects on platelets. Aged garlic extract, but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans, an event believed to be a significant factor in the development of atherosclerosis. Ginkgo may reduce the risk of atherosclerosis by interfering with a chemical the body sometimes makes in excess, called platelet activating factor (PAF). PAF stimulates platelets to stick together too much; ginkgo stops this from happening. Ginkgo also increases blood circulation to the brain, arms, and legs. Garlic and ginkgo also decrease excessive blood coagulation. Both have been shown in double-blind and other controlled trials to decrease the overactive coagulation of blood that may contribute to atherosclerosis. Guggul has been less extensively studied, but double-blind evidence suggests it can significantly improve cholesterol and triglyceride levels in people. Numerous medicinal plants and plant compounds have demonstrated an ability to protect LDL cholesterol from being damaged by free radicals. Garlic, ginkgo, and guggul are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans. Several other herbs have been shown in research to lower lipid levels. Of these, psyllium has the most consistent backing from multiple double-blind trials showing lower cholesterol and triglyceride levels. The evidence supporting the ability of fenugreek to lower lipid levels is not as convincing, coming from preliminary studies only. Since oxidation of LDL cholesterol is thought to be important in causing or accelerating atherosclerosis, and green tea protects against oxidation, this herb may have a role in preventing atherosclerosis. However, while some studies show that green tea is an antioxidant in humans, others have not been able to confirm that it protects LDL cholesterol from damage. Much of the research documenting the health benefits of green tea is based on the amount of green tea typically drunk in Asian countries—about three cups per day (providing 240–320 mg of polyphenols). The research on ginger’s ability to reduce platelet stickiness indicates that 10 grams (approximately 1 heaping teaspoon) per day is the minimum necessary amount to be effective. Lower amounts of dry ginger, as well as various levels of fresh ginger, have not been shown to affect platelets. Turmeric’s active compound curcumin has shown potent anti-platelet activity in animal studies. It has also demonstrated this effect in preliminary human studies. In a similar vein, bilberry has been shown to prevent platelet aggregation as has peony. However, none of these three herbs has been documented to help atherosclerosis in human trials. Butcher’s broom and rosemary are not well studied as being circulatory stimulants but are traditionally reputed to have such an action that might impact atherosclerosis. While butcher’s broom is useful for various diseases of veins, it also exerts effects that are protective for arteries.
Also indexed as: Dyslipidemia, Dyslipidemic Diet, Hypercholesterolemia, Hypercholesterolemic Diet, Hyperlipoproteinemia Although it is by no means the only major risk factor, elevated serum cholesterol is clearly associated with a high risk of heart disease. >BR>Most doctors suggest cholesterol levels should stay under 200 mg/dl. Cholesterol levels lower than 200 mg/dl are not without risk, however, as many people with levels below 200 have heart attacks.
Medical laboratories now subdivide total cholesterol measurement into several components, including LDL (“bad”) cholesterol, which is directly linked to heart disease, and HDL (“good”) cholesterol, which is protective. The relative amount of HDL to LDL is more important than total cholesterol. For example, it is possible for someone with very high HDL to be at relatively low risk for heart disease even with total cholesterol above 200. Evaluation of changes in cholesterol requires consultation with a healthcare professional and should include measurement of total serum cholesterol, as well as HDL and LDL cholesterol. The following discussion is limited to information about lowering serum cholesterol levels using natural approaches. Because high cholesterol is linked to atherosclerosis and heart disease, people concerned about heart disease should also read the article on atherosclerosis. What are the symptoms of high cholesterol? This condition does not produce symptoms. Therefore, it is prudent to visit a health professional on a regular basis to have cholesterol levels measured.
How is it treated? People with high cholesterol are commonly advised to reduce their consumption of dietary cholesterol and saturated fats. In addition, cholesterol-lowering medications, such as bile acid sequestrants (e.g., cholestyramine [Questran®] and colestipol [Colestid®]) and HMG-CoA reductase inhibitors (e.g., atorvastatin [Lipitor®], cerivastatin [Baycol®], fluvastatin [Lescol®], lovastatin [Mevacor®], pravastatin [Pravachol®], and simvastatin [Zocor®]) are often prescribed. For women who have gone through menopause, conventional treatment may also include hormone replacement therapy. Dietary changes that may be helpful: Eating animal foods containing saturated fat is linked to high cholesterol levels and heart disease. Significant amounts of animal-based saturated fat are found in beef, pork, veal, poultry (particularly in poultry skins and dark meat), cheese, butter, ice cream, and all other forms of dairy products not labeled “fat free.” Avoiding consumption of these foods reduces cholesterol and has been reported to reverse even existing heart disease. Unlike other dairy foods, skimmed milk, nonfat yogurt, and nonfat cheese are essentially fat-free. Dairy products labeled “low fat” are not particularly low in fat. A full 25% of calories in 2% milk come from fat.(The “2%” refers to the fraction of volume filled by fat, not the more important percentage of calories coming from fat.) In addition to large amounts of saturated fat from animal-based foods, Americans eat small amounts of saturated fat from coconut and palm oils. Palm oil has been reported to elevate cholesterol. Research regarding coconut oil is mixed, with some trials finding no link to heart disease, while other research reports that coconut oil elevates cholesterol levels. Despite the links between saturated fat intake and serum cholesterol levels, not every person responds to appropriate dietary changes with a drop in cholesterol. A subgroup of people with elevated cholesterol who have what researchers call “large LDL particles” has been reported to have no response even to dramatic reductions in dietary fat. (LDL is the “bad” cholesterol most associated with an increased risk of heart disease.) This phenomenon is not understood. People who significantly reduce intake of animal fats for several months but do not see significant a reduction in cholesterol levels should discuss other approaches to lowering cholesterol with a doctor. Yogurt, acidophilus milk, and kefir are fermented milk products that have been reported to lower cholesterol in most, but not all, double-blind and other controlled research. Until more is known, it makes sense for people with elevated cholesterol who consume these foods, to select nonfat varieties. Eating fish has been reported to increase HDL cholesterol and is linked to a reduced risk of heart disease in most, but not all, studies. Fish contains very little saturated fat, and fish oil contains EPA and DHA, omega-3 fatty acids that appear to protect against heart disease.
Vegetarians have lower cholesterol and less heart disease than meat eaters, in part because they avoid animal fat. Vegans (people who eat no meat, dairy, or eggs) have the lowest cholesterol levels, and switching from a standard diet to a vegan diet, along with other lifestyle changes, has been reported to reverse heart disease in controlled research. However, eating eggs does not increase serum cholesterol as much as eating foods high in saturated fat, and eating eggs may not increase serum cholesterol at all if the overall diet is low in fat. Egg consumption does not appear to be totally safe, however, even for people consuming a low-fat diet. When cholesterol from eggs is cooked or exposed to air, it oxidizes. Oxidized cholesterol is linked to increased risk of heart disease. Eating eggs also makes LDL cholesterol more susceptible to damage, a change linked to heart disease. Whether or not egg eaters are more likely to die from heart disease is a matter of controversy. In one preliminary stu |