Vitamin C

As many as 70 percent of the population is taking supplements, mostly vitamins, convinced that the pills will make them healthier.
But researchers say that vitamin supplements cannot correct for a poor diet, that multivitamins have not been shown to prevent any disease and that it is easy to reach high enough doses of certain vitamins and minerals to actually increase the risk of disease.
No longer, the experts say, are they concerned about vitamin deficits. "Certainly," he said, "by consuming supplements, people can reach that level."
Until recently, there was little concern about vitamin A and bone health."
Researchers say the questions involve multivitamins taken by healthy people, not specific vitamins or minerals taken by groups with specific needs. Dr. Annette Dickinson, president of the Council for Responsible Nutrition, a group that represents the supplement industry, says 70 percent of Americans sometimes take supplements usually multivitamins or individual vitamins and minerals and 40 percent take them regularly.
Scientists once thought those vitamins could help prevent ailments like cancer and heart disease, but rigorous studies found no such effects.
Vitamin E supplements can increase the risk of heart attacks and strokes, and studies of vitamin C supplements consistently failed to show that it had any beneficial effects.
Excess vitamin C is excreted in the urine, but excesses of some other vitamins are stored in fat, where they can build up. Of particular concern, researchers say, is vitamin A. Several recent large studies indicate that people with high levels of vitamin A in their blood have a greater risk for osteoporosis. People can easily reach a potentially dangerous level, about five times the recommended dose, by taking vitamins and supplements, nutrition researchers say. Others warn about overdosing on other vitamins and minerals.
Studies have suggested that high levels of folic acid can protect against heart disease by lowering levels of another substance, homocysteine. High levels of homocysteine are associated with increased risks of heart disease, but there is no study showing definitively that reducing homocysteine levels protects against heart disease.
"People ask me what vitamins I take," she said. Dr. Caballero also does not take vitamins. Dr. Caballero also notes that large, rigorous studies that were supposed to show that individual vitamins prevented disease ended up showing the opposite. A large study of vitamin E and heart disease found that it did not prevent heart attacks and that people taking it had more strokes.
Another study, of women with heart disease, found that antioxidant vitamins might actually increase the rate of atherosclerosis.
Dr. Caballero said people were deluding themselves if they thought multivitamins could make up for poor diets.
"If you eat junk food every day, vitamins are the least of your problems," he said. We tried beta carotene, vitamin E and antioxidants, and they didn't work.