We're in the middle of a nutrition evolution that's making many of the recommended dietary allowance (RDA) tables available on the Web obsolete.

That's because the Food and Nutrition Board (FNB) of the National Academy of Sciences updates its recommendations for all known nutrients on a regular basis. As part of the current cycle of revisions, the recommendations for calcium, phosphorus, magnesium, vitamin D, fluoride, thiamin, riboflavin, niacin, vitamin B-6, folate, vitamin B-12, pantothenic acid, biotin, and choline were evaluated and updated last year. Currently, the FNB and its advisors are assessing human needs for the antioxidant nutrients, such as vitamin C.

During this update cycle, the FNB is also replacing the RDAs, which were set at levels to prevent nutritional deficiencies, with a new set of standards called the Dietary Reference Intakes, or DRIs. The DRIs are expected to differ from the RDAs in that they will also address the role of nutrients in reducing the risk of chronic diseases, such as osteoporosis, cancer, and cardiovascular disease. Also being established are standards of tolerance, called the Upper Limit, or UL, which will be set at a level to guard against nutrient overload and toxicity from concentrated sources, such as supplements.