High-dose vitamin D recommended for over 65s

By Laura Cowen

Meta-analysis findings support recommendations from the Institute of Medicine that people aged 65 years and older should routinely receive 800 IU of vitamin D per day.

The review of data from 11 double-blind, randomized, controlled trials of oral vitamin D supplementation (daily, weekly, or every 4 months), with or without calcium, showed that high-dose vitamin D supplementation (≥800 IU per day) reduced hip fracture risk by approximately 30% compared with placebo or calcium alone.

Lead author Heike Bischoff-Ferrari (University Hospital Zurich, Switzerland) and colleagues say that universal vitamin D supplementation is one strategy to prevent the increasing incidence of hip fractures in people over 65 years of age, but the benefits of this strategy are unclear.

The aim of the analysis was to estimate the effects of vitamin D supplementation on hip and nonvertebral fractures according to the actual intake of each participant, rather than the dose to which the participant was randomly assigned.

The study included data for 31,022 individuals (mean age 76 years; 91% women) with 1111 incident hip fractures and 3770 nonvertebral fractures.

Intention-to-treat analysis showed that participants who were randomly assigned to receive vitamin D had a nonsignificant 10% reduction in hip fracture risk and a significant 7% reduction nonvertebral fracture risk compared with those assigned to control groups. This risk reduction did not differ according assigned treatment dose.

However, when the researchers conducted the analysis according to actual vitamin D intake, individuals in the highest intake quartile (median 800 IU daily; range 792 to 2000 IU) had a significant 30% reduction in the risk hip fracture risk and a 14% reduction in nonvertebral fracture risk, compared with controls.

These findings indicate that "results of typical intention-to-treat analyses… underestimate the benefit of vitamin D supplementation," write Bischoff-Ferrari and co-authors in The New England Journal of Medicine.

Of note, there was no reduction in the risk of hip fracture at any actual-intake level lower than 792 IU per day.

Subgroup analyses revealed that the benefits of the highest level of vitamin D intake were consistent across groups defined by age, type of dwelling, baseline 25-hydroxyvitamin D level, and additional calcium intake.

Commenting on the findings in an accompanying editorial, Robert Heaney (Creighton University Medical Center, Omaha, Nebraska, USA) concluded: "Given the congruence of the findings of this latest meta-analysis with the guidelines from the Endocrine Society, it would appear to be prudent, and probably helpful as well, to ensure an intake at the upper end of the range at which Bischoff-Ferrari et al. found a reduction in fracture risk."

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