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As vitamin research surges, confusion swirls around two basic questions: How much of these nutrients is needed, and what's the best way to get them -- in food or in supplements? For half a century, Americans' vitamin intake has been guided by the Recommended Daily Allowances, or RDAs. Introduced during World War II as a way to ensure that military recruits did not suffer from malnutrition, the levels quickly became a standard for the general population. Technically the National Academy of Sciences sets different RDAs for people of different ages and sexes, but to simplify matters, the FDA has since 1968 taken the highest RDAs -- those appropriate for teenage boys -- and endorsed them as the national standard. These are the numbers that appear on cereal boxes.
Two years ago, the FDA announced plans to change this policy. Instead of endorsing an allotment appropriate to ravenous, fast-growing teenage males, it would simply average the RDAs for different age groups. The new figures are considerably lower and, says the agency, are a better barometer of the typical American's nutritional needs. Essentially they reflect the requirements of adult women. The agency has proposed slashing the RDAs for many vitamins, including A, B, C and E, as well as nutrients such as iron, by 10% to 80%. The < RDA would also acquire a new name: the Reference Daily Intake, or RDI. (On food labels the RDI would be listed as the Daily Value, or DV.) "By using the old RDAs, you're trying to make the entire population consume more nutrients than it needs," explains John Vanderveen, director of the FDA's nutrition division. "Young males need more nutrients than women, children and the elderly."
But the move to slash RDAs, scheduled to go into effect next year, flies in the face of research that suggests benefits from higher doses of vitamins. The current RDA for vitamin C, for example, is 60 mg. But to get a protective effect against cataracts or cancer may require as much as 100 mg. Similarly, vitamin E may need a boost from the RDA of 10 mg to 100 mg. (There is no RDA for beta carotene, but scientists speculate that 25 mg or more a day could be needed.)
Already many people consider the old RDAs, with their focus on preventing scurvy and other rare deficiency problems, to be irrelevant to real health needs. "Our clientele generally thinks of the RDA as a kind of joke," says Sandy Gooch, owner of the chain of seven Mrs. Gooch's markets in Southern California. What's actually needed, vitamin advocates suggest, is guidelines for optimal consumption. That amount may very well depend upon age, sex and life-style habits.
Do people have to take supplements to get enough vitamins? Nutritionists and doctors agree that everyone's basic needs could be met by eating a diet rich in vegetables and fruits. The U.S. government's 1990 dietary guidelines urge an ambitiously varied meal plan: three to five servings daily of vegetables, two to four of fruit, as well as six to 11 of breads, rice, pasta and grains and two to three of meat, eggs, poultry and dried beans.