Answer :Elizabeth Johnson, PhD, a scientist in Tufts HNRCA Carotenoids and Health Laboratory, replies, Vitamin A in supplements may come from retinol, beta-carotene or both. Recent research suggests there may be an association between higher retinol intakes (5,000 IU/day) and an increased risk of osteoporosis in older men and women. However, vitamin A intakes from beta-carotene have not been associated with an increased risk of osteoporosis. The Food and Nutrition Board of the Institute of Medicine set the RDA for vitamin A at 2,310 IU for women and 3,000 IU for men. The tolerable upper level of vitamin A intake for adults is 10,000 IU/day of preformed vitamin A. There is no tolerable upper level of intake for beta-carotene. In general, multivitamin supplements contain no more than 2,500 IU of vitamin A. Often this will be as both retinol (in the form of retinyl acetate) and beta-carotene. If you choose to take supplements containing more than 2,500 IU, it may be best to choose one that contains at least 50% of the vitamin A as beta-carotene. For most people, there is no added benefit in consuming vitamin A at levels above the RDA.
