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Too Much or Too Little Vitamin A Raises Hip-Fracture Risk in Post-Menopausal Women: Presented at ENDO

By Maggie Schwarz

PHILADELPHIA, PA -- June 24, 2003 -- Both high and low levels of vitamin A place postmenopausal women at increased risk for hip fracture, it was reported here on June 20^th at the Endocrine Society's 85^th Annual Meeting.

"This is the first time that a study has demonstrated increased hip fractures at both ends of the vitamin-A concentration curve," said Alexander R. Opotowsky, MD, from the College of Physicians and Surgeons at Columbia University, in New York, conducted a 22-year follow-up study of data from the National Health and Nutrition Examination Study (NHANES) I Epidemiologic Follow-Up Study (1971-1974).

Each of 2,799 women (aged 50 to 74 years) had vitamin A measured at the start of NHANES, a U.S. government study. Over the next two decades, 179 of these women had at least one hip fracture. Those with the highest vitamin A levels were about twice as likely as those with average vitamin A levels to sustain a hip fracture, agreeing with recent studies.

Drs. Opotowsky, who conducted the study with, John P. Bilezikian, from the same institution, also found that women in the lowest vitamin A group had almost twice the risk of having a hip fracture as women in the middle group.

When baseline serum vitamin A levels were divided into quintiles, the researchers found that the highest and lowest quintiles were at twice the risk of hip fracture compared to the middle quintile. These results remained significant after controlling for weight, race, use of hormone replacement, smoking, level of recreational activity, dietary calcium intake and history of previous fractures.

Both high and low serum vitamin A increased the risk of hip fracture more significantly among current smokers than among former and never smokers, Dr. Opotowsky said.

He added that NHANES I contained inadequate information to estimate dietary vitamin A intake.

The investigators noted that they hope these new results prompt the medical community to reassess recent calls to decrease vitamin A supplementation in the general population. Dr. Opotowsky explained that, for some people, vitamin A supplementation may increase fracture risk, while for people with low vitamin A levels, supplementation may be of benefit.

"Our analysis suggests that small amounts of vitamin A may not influence overall hip-fracture rates. However, without knowing the vitamin A status of an individual, eliminating vitamin A supplements could actually increase the number of vitamin A-deficient individuals, which would put them at risk not only of hip fractures, but also for other health risks associated with low vitamin A," he explained.


[Study title: Serum Vitamin A and Hip Fractures: Increased Risk at Both Ends of the Concentration Curve. Abstract OR21-3]

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