High-dose vitamin D prevents fractures

• Frequency and dosage of vitamin D key to protective effect

• Optimal 25-hydroxyvitamin D level for fracture prevention may be 6 nmol/L

Taking high-dose vitamin D daily-with or without calcium-helps prevent hip and nonvertebral fractures in adults aged 65 and older, according to findings from an international study. Both dosage and frequency impact outcome.

Published in The New England Journal of Medicine, the pooled analysis of 11 double-blind, randomized, controlled trials revealed that 800 IU daily vitamin D, but not lower amounts, decreased risk of hip fracture by about 30% and risk of any nonvertebral fracture by about 14%. The reductions were independent of assigned treatment dose of vitamin D, age, sex, additional calcium intake, whether the subjects lived at home or in an institution, and baseline levels of vitamin D.

Frequency, however, did matter. To reap the benefits, patients must take adequate amounts of vitamin D at least quarterly, if not weekly or daily.

The report also suggests that too much calcium-in excess of 1,000 mg daily-can weaken the benefit of vitamin D. Patients should be cautioned to monitor their calcium intake to ensure that with food and supplements combined, they do not exceed the 1,000 mg-per-day limit.

The analysis involved more than 31,000 people with 1,111 hip fractures and 3,770 nonvertebral fractures. The researchers explained that unlike other studies on the topic, theirs looked at amounts of vitamin D actually taken rather than those participants were supposed to take.

The findings are in line with the Institute of Medicine’s recent recommendation that individuals age 65 years and older take 800 IU vitamin D daily, but suggest that a 25-hydroxyvitamin D level of more than 60 nmol/L is optimal for reducing risk of fractures.

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