Dear Eating Right: After reading an article in The Times about diet and Recommended Dietary Allowances, I have a question concerning vitamin pills and their labels. Based on the information on the labels, some vitamins supply more than 1,666% of the "U.S. Recommended Daily Allowance." How is this different from the Recommended Dietary Allowances referred to in the article?
--PHILIP RICHARDS, Malibu
Dear Philip: There is a great difference between the two.
The first Recommended Dietary Allowances were developed during World War II when many Americans were found to be malnourished. To make sure the allowances would safely cover most healthy people, suggestions for daily nutrient needs were set high enough to cover people of all ages.
But since that time, suggested levels have been raised or lowered according to the latest scientific research. Advice for nutrients is now given by age group: infants and children are separated from men and women. The RDA table has also been expanded; the 10th and most current edition, published in 1989, gives recommendations for protein, 11 vitamins and seven minerals. The committee added two new nutrients: Vitamin K for its role in normal blood clotting and the trace mineral selenium, which may contribute to heart health.
Another difference: In most cases, the RDA table lists nutrients in milligrams (although micrograms are occasionally given). On the other hand, the U.S. Recommended Daily Allowances (USRDA) are listed as percentages. This is because they were developed primarily for use on product labels and vitamin pills, so that all the RDAs wouldn't have to be printed. They represent the highest RDA of a given nutrient. (As part of the Food and Drug Administration's proposed food labeling changes, the USRDA will be replaced by the terms Reference Daily Intake and Daily Reference Values.)
For example, the RDA of Vitamin A for a woman is 800 retinol equivalents (RE), whereas a man's is 1,000. Instead of reading that a serving of food contains "800 RE" of Vitamin A, it is expressed as a percentage of the RDA or 80%.
Vitamin pills are a little different. This is because vitamins are a concentrated form of nutrients and the RDAs are intended to be met by the nutrients in food. A brand of Super B complex may contain 100 micrograms of Vitamin B-12. This supplies more than 1,000% of the USRDA for that nutrient because the RDA is just 2 micrograms.
