To prevent fractures find the right dose of vitamin D

July 1, 2005

An oral dose of 400 IU/d of vitamin D (cholecalciferol) just isn't enough to prevent fractures in older persons; but 700 to 800 IU/d appears to reduce the risk of hip and nonvertebral fractures by about one quarter, when compared with calcium or placebo, according to a meta-analysis of randomized controlled trials (RCTs).

An oral dose of 400 IU/d of vitamin D (cholecalciferol) just isn't enough to prevent fractures in older persons; but 700 to 800 IU/d appears to reduce the risk of hip and nonvertebral fractures by about one quarter, when compared with calcium or placebo, according to a meta-analysis of randomized controlled trials (RCTs).

After reviewing three RCTs involving more than 5,500 persons, Boston investigators determined that the higher dosage of vitamin D-taken with or without calcium-reduced the relative risk of hip fracture by 26% (pooled RR 0.74) when compared with only calcium or placebo. Similarly, upon reviewing five RCTs involving 6,098 persons, they calculated that 700 to 800 IU/d of vitamin D reduced the risk of any nonvertebral fracture by 23% (pooled RR 0.77) versus calcium or placebo. Put another way, 45 persons would need to be treated with 700 to 800 IU/d of vitamin D to prevent one person from sustaining a hip fracture, and 27 would need to receive the same dosage to prevent one nonvertebral fracture. Results do not appear to differ by sex. By way of contrast, the researchers were unable to find any RCTs that showed a 400 IU/d dose could reduce hip or vertebral fractures.

Because calcium was given in addition to vitamin D in all but one of the trials, the investigators were unable to fully determine the independent effect of vitamin D. They surmise that dietary calcium intakes of more than 700 mg/d in addition to the vitamin D may be necessary to achieve at least nonvertebral fracture protection. They concluded that given the high morbidity, mortality, and cost associated with fractures and the relatively low cost of vitamin D, daily vitamin D supplementation may be well worth recommending in elderly ambulatory and institutionalized persons.