Vitamin D supplements associated with reduced fracture risk in older adults

Oral vitamin D supplements at a dose of at least 400 international units per day are associated with a reduced risk of bone fractures in older adults, according to results of a meta-analysis published in the March 23 issue of Archives of Internal Medicine.

“The anti-fracture benefits of vitamin D have been questioned by several recent trials, leading to uncertainty among patients and physicians regarding recommendations for vitamin D supplementation,” the authors wrote in their study. “Factors that may obscure a benefit of vitamin D are low adherence to treatment, low dose of vitamin D or the use of less potent ergocalciferol (vitamin D2).”

Heike A. Bischoff-Ferrari, DrPH, of the University of Zurich and University Hospital in Zurich, and colleagues performed a meta-analysis on 12 previously published clinical trials of oral vitamin D supplements among adults age 65 or older. These double-blind randomized controlled trials involved 42,279 participants (average age 78) and looked at non-vertebral (non-spinal) fractures, including eight trials of 40,886 participants. The researchers focused on hip fractures, according to a press release.

When the results of the trials were pooled, vitamin D supplements decreased the risk of non-vertebral fractures by 14% and hip fractures by 9%. The investigators then pooled the results of only the nine trials in which participants received doses of more than 400 international units per day. At this dosage, vitamin D supplements reduced non-vertebral fractures by 20% and hip fractures by 18%.

The researchers reported a greater reduction in risk among trial participants whose blood levels of 25-hydroxyvitamin D — a commonly used measure of blood vitamin D levels — increased the most.

Doses of 400 international units per day or lower did not reduce the risk of either fracture type, according to the press release. Among individuals taking high doses of vitamin D, additional calcium did not appear to have any further protective effect against fractures.

“Physiologically, the calcium-sparing effect of vitamin D may explain why we did not see an additional benefit of calcium supplementation at a higher dose of vitamin D,” the authors wrote.

“The greater fracture reduction [achieved] with a higher received dose or higher achieved 25-hydroxyvitamin D levels for any non-vertebral fracture or hip fracture suggests that higher doses of vitamin D should be explored in future research to optimize anti-fracture efficacy,” they said in the press release. “Also, it is possible that greater benefits may be achieved with earlier initiation of vitamin D supplementation and longer duration of use. [However] our results do not support use of low-dose vitamin D with or without calcium in the prevention of fractures among older individuals.”

Reference:
Bischoff-Ferrari HA, Willett WC, Wong JB, et al. Prevention of nonvertebral fractures with oral vitamin D and dose dependency: A meta-analysis of randomized controlled trials. Arch Intern Med. 2009;169[6]:551-561.