Vitamins: More May Be Too Many
By GINA KOLATA
A growing number of medical experts are concerned that Americans are overdoing their vitamin consumption. 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. Those are almost unheard of today, even with the population eating less than ideal diets and skimping on fruits and vegetables. Instead, the concern is with the dangers of vitamin excess.
"There has been a transition from focusing on minimum needs to the reality that today our problem is excess excess calories and, yes, excesses of vitamins and minerals as well," said Dr. Benjamin Caballero, a member of the Food and Nutrition Board at the National Academy of Sciences and the director of the Center for Human Nutrition at Johns Hopkins University.
Dr. Caballero said that for some supplements, including vitamin A, the difference between the recommended dose and a dose that could lead to bad outcomes like osteoporosis was not large. Popular multivitamins, he added, often contain what could be risky doses.
"Certainly," he said, "by consuming supplements, people can reach that level."
Doctors who once told patients that multivitamins were, at worst, a waste of money now say they are questioning that idea.
"All of a sudden, scientists are rearing back and saying, `Wait a minute, do we really know that we need this and do we really know that we need that?' " said Dr. Ruth Kava, nutrition director at the American Council on Science and Health, a consumer foundation in Manhattan that is in part financed by industry.
With vitamin A in particular, it is easy to step over the edge into a danger zone, said Dr. Joan McGowan, chief of the musculoskeletal diseases branch at the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
"You can be eating Total cereal, drinking fortified milk, taking a multivitamin," Dr. McGowan said. "You can get into a situation where you're getting more than you need. Until recently, there was little concern about vitamin A and bone health."
Now, she added, "we may have to rethink the issues."
Similar questions are being raised about other vitamins and minerals, notably iron and vitamins E and C.
Researchers say the questions involve multivitamins taken by healthy people, not specific vitamins or minerals taken by groups with specific needs. Some elderly people, for example, may be deficient in vitamin B12 because they lose their ability to absorb it from foods. People who spend little time outdoors may require vitamin D, which the skin makes when it is exposed to sunlight. Even when older people are in the sun, aging skin loses much of its ability to synthesize the vitamin.
Pregnant women who do not receive enough folic acid, a vitamin in fruits and vegetables that is added to enriched flour, are at increased risk of having babies with neural tube defects. Because the vitamin is needed at the very start of pregnancy, some advocate folic acid supplements for all who might become pregnant, just to be sure they are protected.
For most people, however, the issue is not deficits. Instead, nutrition researchers ask: Do people eating relatively healthy diets with fresh fruits and vegetables and not too many calories or fats benefit from multivitamins or other supplements? Do those whose diets are abysmal, heavy on fast foods and lacking in fruits and vegetables, make up for some deficits if they take multivitamin pills?
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.
"Our position," she said, "is that most people, literally most people, would benefit from taking a multivitamin every day. It's insuring adequate and even generous intake of all the nutrients."