Vitamin A - plentiful in foods like yams, carrots, asparagus, and eggs - has many health benefits as an antioxidant, such as good vision and healthy skin. However, eating too much vitamin A has been shown to have negative side effects.
Long-term, regular ingestion of excessive doses of vitamin A may lead to an increased risk for osteoporosis and hip fracture.
From 1980 to 1998, the authors of a recent study in the Journal of the American Medical Association examined over 70,000 women between the ages of 34-77. Hip fractures were recorded, excluding severe trauma cases like car accidents in which fracture was unavoidable; fractures were compared to the women's diets regarding vitamin A intake from foods and supplements over the 18 years.
Women in the group with the highest overall vitamin A intake from foods and supplements combined were almost 50% more likely to suffer hip fractures than women with the lowest intake. Women with the highest intake of retinol (pure vitamin A) from multivitamins/supplements were approximately 90% more likely to experience hip fracture. A full 21% of the women in the study consumed more than the "tolerable upper limit" of vitamin A, nearly all from supplements.
This study offers further evidence that excessive vitamin A consumption, particularly from supplements, may cause osteoporosis in women. The best way to limit your vitamin A intake is to obtain it only from foods, in its beta-carotene form. Besides increasing fracture risk, excessive levels of vitamin A can be toxic and even fatal.
Feskanich D, Singh V, Willett WC, et al. Vitamin A intake and hip fractures among postmenopausal women. Journal of the American Medical Association 2002:287(1), pp. 47-54.
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