Both high and low levels of vitamin A can increase hip fractures in older women, reported researchers at a scientific meeting in the US last week.
Recent studies have shown that high intake of vitamin A can be associated with lower bone density and increased risk of fracture. However the new results suggest that recent calls to decrease vitamin A supplementation may need to be reassessed, said Dr Alexander Opotowsky, the lead investigator in the study, at the US Endocrine Society's annual meeting in Philadelphia on Friday.
Investigators at Columbia University's College of Physicians and Surgeons in New York City sought to determine whether high and low levels of vitamin A placed postmenopausal women at an increased risk for hip fractures. They identified 179 women from the United States government's NHANES I survey who experienced hip fractures during the study and follow-up. These women were divided into five groups, or quintiles, based on their vitamin A levels.
"Women with the highest vitamin A levels and lowest vitamin A levels were both twice as likely to experience a hip fracture when compared with women who had average levels of vitamin A," said Dr Opotowsky. "This is the first time that a study has demonstrated increased hip fractures at both ends of the vitamin A concentration curve."
He added that for some people, vitamin A supplements may increase fracture risk, but for people with low vitamin A levels, supplementation may be a 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 further risk not only for hip fractures, but also for other health risks associated with low vitamin A," explained Dr Opotowsky.
The UK's Health Food Manufacturers' Association currently sets the Upper Safe Level (USL) for daily vitamin A supplementation at 2300 ug, while the Food Standards Agency's recently commissioned report from the Expert Group on Vitamins and Minerals reduces this to 1500ug. Europe's Scientific Committee on Food (SCF) recommends a total daily intake of not more than 3000ug.