Comparison of vitamin D ₂ and vitamin D ₃ supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis ^{1 2 3}

Abstract

Background: Currently, there is a lack of clarity in the literature as to whether there is a definitive difference between the effects of vitamins D ₂ and D ₃ in the raising of serum 25-hydroxyvitamin D [25(OH)D].

Objective: The objective of this article was to report a systematic review and meta-analysis of randomized controlled trials (RCTs) that have directly compared the effects of vitamin D ₂ and vitamin D ₃ on serum 25(OH)D concentrations in humans.

Design: The ISI Web of Knowledge (January 1966 to July 2011) database was searched electronically for all relevant studies in adults that directly compared vitamin D ₃ with vitamin D ₂. The Cochrane Clinical Trials Registry, International Standard Randomized Controlled Trials Number register, and clinicaltrials.gov were also searched for any unpublished trials.

Results: A meta-analysis of RCTs indicated that supplementation with vitamin D ₃ had a significant and positive effect in the raising of serum 25(OH)D concentrations compared with the effect of vitamin D ₂ ( P = 0.001). When the frequency of dosage administration was compared, there was a significant response for vitamin D ₃ when given as a bolus dose ( P = 0.0002) compared with administration of vitamin D ₂, but the effect was lost with daily supplementation.

Conclusions: This meta-analysis indicates that vitamin D ₃ is more efficacious at raising serum 25(OH)D concentrations than is vitamin D ₂, and thus vitamin D ₃ could potentially become the preferred choice for supplementation. However, additional research is required to examine the metabolic pathways involved in oral and intramuscular administration of vitamin D and the effects across age, sex, and ethnicity, which this review was unable to verify.