NEW YORK (Reuters Health) - A single high dose of vitamin D given every four weeks is as safe as smaller daily or weekly doses, and is as effective in achieving adequate circulating levels of the vitamin, according to a study conducted in Israel.
To prevent fractures in older patients, the level of the active metabolite of vitamin D -- that is, 25-hydroxyvitamin D -- should be higher than 30 nanograms per milliliter, Dr. Sophia Ish-Shalom and colleagues explain in the Journal of Clinical Endocrinology and Metabolism.
While monthly dosing could make it easier for people to stick to regular vitamin D supplementation, the researchers were concerned that a large dose might lead to a spike in calcium levels in the blood -- which could cause problems.
To check, the team conducted a clinical trial with 48 women, 81 years of age on average, who had undergone surgery to repair a hip fracture, to compare three dosing regimens of vitamin D supplementation: 1,500 International Units once daily, 10,500 IU once weekly, or 45,000 IU every 28 days.
After two months, blood levels of 25-hydroxyvitamin D were similar at 33.2, 29.2, and 37.1 nanograms per milliliter, respectively.
A single instance of excessive blood levels of calcium occurred, in a patient assigned to the daily supplement.
Ish-Shalom, at Rambam Medical Center in Haifa, Israel, and associates conclude that "the choice of dose frequency can be based on whichever approach will optimize an individual's adherence" to regular vitamin D supplementation.
SOURCE: Journal of Clinical Endocrinology and Metabolism, September 2008.