Women with higher or lower blood levels of vitamin A than average appear to be at increased risk of hip fracture, according to a report in the American Journal of Medicine.

Drs. Alexander R. Opotowsky and John P. Bilezekian of Columbia University, New York, note that high intake of vitamin A, and high blood levels, have already been linked to increased fracture risk. However, their particular interest was in low-normal concentrations.

The researchers examined data from the first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study for 2799 women who were 50 to 70 years of age at enrollment. There were 172 hip fractures over the following 22 years.

The investigators found that there was a U-shaped relationship between vitamin A levels and hip fractures.

That is to say, compared with those with average concentrations of vitamin A, women with the lowest concentrations had a 90 percent higher risk of fracture and those with the highest concentrations had double the risk.

“At both ends of the spectrum, the skeleton can be harmed,” Bilezekian told Reuters Health. “Vitamin A should be used within the recommended daily allowance figures as provided by the Food and Nutrition Board and other authoritative health agencies.”

SOURCE: American Journal of Medicine, August 1, 2004.