TORONTO – A daily vitamin D dose of at least 792 IU was linked with significantly reduced rates of nonvertebral fractures and hip fractures in a meta-analysis of data from 11 randomized, controlled trials.
But the benefit from vitamin D appeared blunted when combined with a higher calcium dose, or when patients received vitamin D once yearly, Dr. Heike A. Bischoff-Ferrari reported.
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A high-dose vitamin D supplement (792-2,000 IU/day*) with a daily calcium dose below 1,000 mg/day was linked with a significant reduction in nonvertebral fractures, but when the daily calcium supplement delivered 1,000 mg or more, this amount of vitamin D did not associate with any significant change in fracture rate, according to a meta-analysis.
In the meta-analysis, patients in the highest quartile for daily vitamin D intake, 792-2000 IU, had a statistically significant 14% reduced rate of any nonvertebral fracture, and a significant 30% reduced rate of hip fractures, in an analysis that adjusted for age, gender, and type of dwelling, said Dr. Bischoff-Ferrari, a rheumatologist at the University of Zurich.
Her meta-analysis pooled individual participant data from 12 double-blind, randomized, controlled trials that examined the impact of vitamin D supplements on fracture rate in people aged 65 years or older published through June 2010, and for which she could obtain individual participant data. The primary analysis focused on the 11 studies of the 12 in which participants received the supplement at least monthly, with 31,022 people enrolled. The twelfth study tested once annual dosing, and the researchers included those data in a separate analysis. The participants’ average age was 76 years, and about 90% were women.
The analysis divided the study subjects into the control group, with more than 15,000 people, and then into quartiles of their received amount of vitamin D, including both their study-treatment dose and any additional vitamin D intake. The analysis also took into account adherence to treatment. Each vitamin D quartile contained nearly 4,000 people, with a daily dose range of 792-2,000 mg forming the top quartile. Only the top quartile of vitamin intake linked with statistically significant differences, compared with the controls, for any nonvertebral fracture and for hip fracture.
Adding the data from the one trial that tested annual vitamin D treatment to the meta-analysis eliminated the statistically significant effect on fracture rates, suggesting that yearly administration of vitamin D produces a different effect than daily, weekly, or monthly treatment.
An additional analysis that looked at the interaction of calcium supplements along with vitamin D showed that with a daily calcium dose below 1,000 mg/day a high-dose vitamin D supplement (792-2,000 mg/day) linked with a statistically significant reduction in nonvertebral fractures, but when the daily calcium supplement delivered 1,000 mg or more, this amount of vitamin D did not associate with any significant change in fracture rate, suggesting an adverse effect from higher calcium intake.
Dr. Bischoff-Ferrari said that she had no disclosures.
* The units of the dosage range were incorrect in the original story and have been corrected.