I have quit taking Vitamin B, C and E supplements.
The evidence on these remains ambiguous – with many benefits evidenced and some risks. Below are the most recent pieces of contradictory research:
Multivitamins Have No Impact on Risk of Cancer Or Heart Disease in Postmenopausal Women
The largest study of its kind concludes that long-term multivitamin use has no impact on the risk of common cancers, cardiovascular disease or overall mortality in postmenopausal women.
Vitamin E may decrease and increase mortality of male smokers with high dietary vitamin C intake
Six-year vitamin E supplementation decreased mortality by 41% in elderly male smokers who had high dietary vitamin C intake, but increased mortality by 19% in middle-aged smokers who had high vitamin C intake, according to a study published in the American Journal of Epidemiology.
Vitamin B and folic acid may reduce risk of age-related vision loss
Taking a combination of vitamins B6 and B12 and folic acid appears to decrease the risk of age-related macular degeneration in women, according to a report in the February 23 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
But the most confusing piece of research on anti-oxidants was reported recently in the New York Times – and brought to my attention by my brother, Matthew:
Vitamins Found to Curb Exercise Benefits
If you exercise to improve your metabolism and prevent diabetes, you may want to avoid antioxidants like vitamins C and E…
Exercise is known to have many beneficial effects on health, including on the body’s sensitivity to insulin. “Get more exercise” is often among the first recommendations given by doctors to people at risk of diabetes.
But exercise makes the muscle cells metabolize glucose, by combining its carbon atoms with oxygen and extracting the energy that is released. In the process, some highly reactive oxygen molecules escape and make chemical attacks on anything in sight.
These reactive oxygen compounds are known to damage the body’s tissues. The amount of oxidative damage increases with age, and according to one theory of aging it is a major cause of the body’s decline.
The body has its own defense system for combating oxidative damage, but it does not always do enough. So antioxidants, which mop up the reactive oxygen compounds, may seem like a logical solution.
Researchers…. found that in the group taking the vitamins there was no improvement in insulin sensitivity and almost no activation of the body’s natural defense mechanism against oxidative damage.
The reason, they suggest, is that the reactive oxygen compounds, inevitable byproducts of exercise, are a natural trigger for both of these responses. The vitamins, by efficiently destroying the reactive oxygen, short-circuit the body’s natural response to exercise…
“If you exercise to promote health, you shouldn’t take large amounts of antioxidants,” Dr. Ristow said. A second message of the study, he said, “is that antioxidants in general cause certain effects that inhibit otherwise positive effects of exercise, dieting and other interventions.”
The findings appear in this week’s issue of The Proceedings of the National Academy of Sciences.
The effect of vitamins on exercise and glucose metabolism “is really quite significant,” said Dr. C. Ronald Kahn of the Joslin Diabetes Center in Boston, a co-author of the report. “If people are trying to exercise, this is blocking the effects of insulin on the metabolic response.”
The advice does not apply to fruits and vegetables, Dr. Ristow said; even though they are high in antioxidants, the many other substances they contain presumably outweigh any negative effect.
Dr. Kahn said it might be that reactive oxygen is beneficial in small doses, because it touches off the body’s natural defense system, but harmful in higher doses…
