Women who consume high levels of vitamin A may be at a higher risk of osteoporosis, implies a study published in last week’s Journal of the American Medical Association (JAMA).

The study, which was part-financed by pharmaceuticals and vitamin producer Hoffman La Roche, found a link between hip fractures and intake (both from food and dietary supplements) of the basic form of vitamin A in excess of 6,600 international units (IU) per day. As explained in an article in the Washington Post, most multivitamins have 5,000 IU of A, but some is derived from beta carotene, which the body converts into vitamin A. The research found no effect on bone health from vitamin A derived from beta carotene.

Groups active in the dietary supplement industry argue that earlier studies have not shown this effect, and are urging consumers not to cut their vitamin A intake following this report. People who do actively monitor their vitamin consumption may find it difficult to identify how much “straight” vitamin A tablets contain, as some labels do not disclose the A/beta carotene split.

One of the study’s authors, Walter Willett, stated that 5,000 IU could be problematic, in view of the fact that many foods are now enhanced with vitamin A, and the study’s association between excessive vitamin A and impaired bones even at levels lower than 6,600 IU.

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