To the Editor: Dr Feskanich and colleagues1 found that high intake of dietary retinol (ie,
vitamin A) was related to risk of hip fracture in postmenopausal women. They
interpret these data as supportive of but not conclusive of a causal relationship.
The possible risks associated with high intake of retinol were reviewed
in 2001 by the Food and Nutrition Board (FNB) of the Institute of Medicine,2 which found the relevant studies "provocative but
conflicting" and concluded that "they are not useful for setting a UL [upper
limit] for vitamin A." Thus, the FNB suggested an upper limit for vitamin
A of 3000 µg/d of retinol (equivalent to 10 000 IU/d) based on
other effects, such as risk of birth defects, recognized as related to excess
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