New RDA's launched

After four years reviewing scientific research into vitamins and minerals the US Institute of Medicine last week issued a report determining the proper dose of each to optimise health and how much could cause side effects. Here is a sample of the recommended dietary allowances. Vitamin A: RDA, 900 micrograms for men, 700 for women. Found in carrots and other dark-coloured vegetables and fruits. Upper limit, 3,000 micrograms. Vitamin B12: RDA, 2.4 micrograms, the amount in 3 ounces of beef. Many people over 50 lose the ability to absorb B12 from natural food sources and so should consider fortified foods, like cereals, or a supplement. Vitamin C: RDA, 75 milligrams for women, 90 for men. Eight ounces of orange juice yields a day's supply. Smokers need 35 more milligrams. Upper limit, 2,000 milligrams; more can cause diarrhea. Vitamin D: RDA, 200 international units for most people; 400 International Units for people ages 51 to 70. Found in fortified milk. Vitamin E: RDA, 15 milligrams. Upper limit, 1,000 milligrams; higher levels risk uncontrolled bleeding. Folic acid: RDA, 400 micrograms. Found in spinach, orange juice and fortified foods. Because folic acid in the first days of pregnancy prevents certain birth defects, women of childbearing age are routinely advised to take a supplement. Upper limit, 1 milligram a day; more can cause nerve damage. Calcium: RDA for most adults, 1,000 milligrams daily; for teen-agers, 1,300 milligrams; for those over age 50, 1,200 milligrams. Highest food sources are dairy and calcium-fortified orange juice. Vitamin K: RDA, 120 micrograms for men, 90 for women. Found in green leafy vegetables. Iron: RDA, 8 milligrams for men and postmenopausal women. Premenopausal women need 18 milligrams; pregnant women 27 milligrams. Upper limit, 45 milligrams or stomach upset can occur. Zinc: RDA, 11 milligrams for men, 8 for women. Upper limit, 40 milligrams; more can block absorption of another vital nutrient, copper. For RDAs on all vitamins and minerals, search the institute Web site at http://www.nas.edu