Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis

Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, Chope G, HyppÃ¶nen E, Berry J, Vieth R, Lanham-New, S. (2012) Am J Clin Nutr 95(6) 1357-64. doi: 10.3945/ajcn.111.031070.

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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 D2 and D3 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 D2 and vitamin D3 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 D3 with vitamin D2. 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International Standard Randomized Controlled Trials Number register, and clinicaltrials.gov were also searched for any unpublished trials.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 D3 had a significant and positive effect in the raising of serum 25(OH)D concentrations compared with the effect of vitamin D2 (P = 0.001).

When the frequency of dosage administration was compared, there was a significant response for vitamin D3 when given as a bolus dose (P = 0.0002) compared with administration of vitamin D2, but the effect was lost with daily supplementation.

Conclusions:

This meta-analysis indicates that vitamin D3 is more efficacious at raising serum 25(OH)D concentrations than is vitamin D2, and thus vitamin D3) 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.

FAB RESEARCH COMMENT:

This systematic review of human clinical trials found that supplementation with Vitamin D2 (the only form found in plant-derived foods and supplements) was significantly less effective than Vitamin D3 (the form found in animal-derived foods and supplements) in raising blood levels of Vitamin D.

This finding has important implications for health guidelines and recommendations, most of which consider these two forms of Vitamin D to be equivalent, and for the producers of Vitamin D supplements and fortified foods, as well as for vegans and vegetarians.

However, given the differences between indivial trials included in this review, the researchers noted that more research is still needed to clarify the mechanisms underying Vitamin D absoprtion and metabolism, which can vary by delivery mode and dosage; and also to investigate potentially important differences between subgroups defined by sex, age and ethnicity in their response to Vitamin D supplementation.

Vitamin D deficiency or insufficiency is a widepread public health problem, affecting the majority of the population in the UK and most other developed countries during the winter months in particular - as bright sunlight on the skin, not diet, is the main natural source of this multifunctional steroid hormone.

Vitamin D supplements or fortified foods are therefore required to maintain adequate Vitamin D levels, as modern, indoor lifetyles and habits (including the use of sunscreen) do not provide sufficient sunlight exposure for most people, and only a very few foods (such as oily fish) naturally contain any significant amount of Vitamin D.

These findings are particularly important for vegetarians and vegans who rely on the Vitamin D2 form in supplements of fortified foods - as they show that twice the quantity of Vitamin D2 is likely to be needed than has previously been assumed.

For more information on the evidence linking suboptimal Vitamin D status to a wide range of developmental and mental, as well as physical, health conditions - please see the following lists, which are regularly updated.