The supplements implicated are as much as 10 and 20 times the recommended dietary allowances--known as RDAs--updated in 1989 by the National Research Council's Food and Nutrition Board. But Blumberg points out that the RDAs are based on the minimal needs to prevent vitamin or mineral deficiency, not on the needs to maintain health or to prevent disease.
The problem, he says, is that money isn't available to support large-scale, long-term studies. Much of that money comes from private pharmaceutical companies because, with the results, they can patent medications and make money. They can't patent vitamins and minerals, Blumberg says, so the companies are less willing to hand over money for research.
"If you want to make the claim, 'If you take this or that, it'll reduce your risk,' it'll take a 20-, 30-year study," he says. "The data simply isn't there to do anything more than to suggest."
That leaves the public to decide for itself whether to pop extra pills, partly based on whether cancer or heart disease runs in the family, Kenney says.
"Read, think, listen, make informed decisions," Hathcock says. "Those are God, motherhood and apple-pie kinds of recommendations."
Food Sources of Antioxidant Vitamins E, C and Beta-carotene
The Dietary Guidelines for Americans, updated in 1990 by the U.S. Department of Agriculture, call for us to eat a variety of foods so we get a balance of nutrients in our diet. In addition, the guidelines recommend that Americans eat five servings of fruits and vegetables a day, with at least one Vitamin C-rich and one Vitamin A-rich serving. Serving sizes range from half a cup to a cup.
Good dietary sources of Vitamin C are citrus fruits such as oranges and grapefruit, fruit and vegetable juices, tropical fruits such as mangoes and guavas, kiwi fruit, strawberries, plus vegetables such as broccoli, cauliflower and sweet and hot peppers. Recommended Dietary Allowance (RDA): 60 mg. Megadose supplement: 500-1,000 mg.
Good sources of Vitamin E are more limited, especially if someone is trying to lower fat and meat intake. The best dietary sources are nuts such as almonds and hazelnuts, sunflower seeds, wheat germ and vegetable oils. RDA: 30 international units. Megadose supplement: 400-800 IU.
Good dietary sources of beta-carotene, which the body converts to Vitamin A, are carrots, squash, sweet potatoes, green leafy vegetables such as spinach and kale, mangoes, cantaloupes and apricots. RDA: None established. Megadose supplement: 15-30 mg.