For women who consume large amounts of vitamin A, also known as retinol, lowered bone mass and an increased risk of hip fractures may result, say researchers from the Harvard School of Public Health in a recent issue of the Journal of the American Medical Association.
Previous research has shown that too much vitamin A in the diet can suppress the body's ability to make new bone and may actually reduce a person's existing bone mass, thereby increasing the risk of fractures. Researchers studied over 72,000 postmenopausal women for 18 years to assess the relationship between high vitamin A intake from foods and supplements and the risk of hip fractures. The women in the study completed regular food questionnaires and provided information about health habits, use of hormones and supplements and weight.
During the 18-year study period, over 600 women experienced hip fractures. Women who had the highest total vitamin A intake had a significantly higher risk of hip fracture when compared to women who consumed the least amount of vitamin A. The researchers maintained that the increased risk was mainly attributable to retinol, the vitamin A found in foods of animal origin, not beta carotene, which is contained in fruits and vegetables and can be converted to retinol by the body.
Vitamin A, a fat-soluble vitamin, is an important dietary element - it is involved in the formation and maintenance of healthy skin, hair and mucous membranes. How much vitamin A is too much? The 1989 RDA for vitamin A has been set at 800 retinol equivalents (RE) per day for women 19 to 50 years of age, and 1,000 retinol equivalents for men 19 to 50 years of age, so check your multivitamin or supplements to make sure you’re not exceeding that amount. Remember, too, that foods contain vitamin A - one carrot has about 2025 RE of vitamin A, which is 203% of a man's recommended daily intake.
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Sources: Feskanich D, Singh V, Willett WC, Colditz GA. Vitamin A intake and hip fractures among postmenopausal women. Journal of the American Medical Association 2002 Jan 2;287(1):47-54.