Vitamin D supplementation and hip fracture risk

Researchers from Australia and the UK reviewed the evidence.

First, the details.

• The researchers conducted 2 meta-analyses.
  • 7 clinical studies (randomization of patients to a treatment group) of vitamin D supplementation and hip fracture
  • 17 observational studies (1903 cases) of vitamin D blood levels (25-hydroxyvitamin D (25(OH)D) level), parathyroid hormone, and hip fracture.

And, the results.

• Combining data from the clinical studies showed no significant difference in hip fracture risk in those randomly assigned to vitamin D supplementation vs placebo.
  • There was no significant difference between studies based on dose (less than 800 IU/day and at least 800 IU/day).
• The observational studies reported 33% lower vitamin D blood levels in patients compared to controls.
  • This difference was significantly greater in “population” studies compared to “hospital” controls.
• Parathyroid hormone blood levels in hip fracture cases did not differ significantly from controls.

The bottom line?

Vitamin D, regardless of the dose, failed to prevent hip fractures.

The results from the 2 types of studies differ. The authors concluded, “The reason for this is unclear; 1 possible explanation is uncontrolled confounding in observational studies.”

So, the authors lean toward placing more weight on the study results where patients were randomly assigned to a treatment group — no significant difference in hip fracture risk.

Somewhat related to these findings is an earlier review published this year that compared the effect of vitamin D + calcium on fracture risk. Those reviewers concluded, “Vitamin D3 + calcium appears to achieve benefits above those attained with calcium supplementation alone for non-vertebral and non-vertebral-non-hip fractures.”

The abstract from the Australia/UK study doesn’t mention the prevalence of calcium intake.

8/17/10 19:42 JR