High doses of vitamin D may help prevent hip fractures in people 65 and older, according to a review of previous studies that found conflicting evidence of the nutrient’s benefit.
People who took 792 to 2,000 units of the vitamin daily had a 30 percent lower risk of hip fractures, Swiss researchers wrote today in the New England Journal of Medicine. The results support a recommendation by the U.S. Institute of Medicine that older people take at least 800 units of the nutrient a day.
Hip fractures will more than triple among women and quadruple among men by 2050 as the global population ages, the researchers from the Center on Aging and Mobility at University Hospital in Zurich wrote. Previous studies have produced conflicting results, possibly because patients’ actual intake of vitamin D differed from the intended dose, the researchers said. Today’s review showed only people assigned to take 800 units or more had a lower fracture risk.
“Our findings suggest that some previous high-quality trials of vitamin D supplementation either showed no benefit owing to lower-than-intended doses of vitamin D or showed an unexpected benefit owing to higher-than-intended doses,” the researchers said. “Only a high intake of vitamin D leads to a significant reduction in the risk of fracture.”
The review included data from 31,022 participants in 11 studies. The scientists weren’t able to determine the effects of taking vitamin D without calcium, as patients who got high doses of the vitamin also received calcium.
Information on the levels of vitamin D before participating in a trial was available for only 4,383 patients. Having that data is key because giving additional nutrients to people who already have an adequate level, or not giving enough to those with a deficiency, isn’t likely to have any effect, Robert Heaney, a professor of medicine at Creighton University in Omaha, wrote in an editorial accompanying the study.
“The question of how much vitamin D is enough is likely to remain muddled as long as meta-analyses focus on trial methodology rather than on biology,” said Heaney, who helps lead the university’s Osteoporosis Research Center. “It would appear to be prudent, and probably helpful as well, to ensure an intake at the upper end of the range.”
The research was funded by the Swiss National Foundations, the European Commission and DSM Nutritional Products, a unit of Dutch chemical maker Royal DSM NV.