Vitamin D2 (ergocalciferol)

Vitamin D is a fat-soluble vitamin that is naturally found in very few food sources. It is produced endogenously from ultraviolet light from the sun striking the skin and then triggering vitamin D synthesis and activation. Vitamin D helps promote calcium absorption in the gut, maintains adequate serum calcium and phosphate levels, promotes bone growth, modulates cell growth, and has many other roles. There have been an increasing number of people, especially in older adults, with vitamin D deficiency. This is in part a result of a reduction of sun exposure as people age, increase in use of sunscreen, and other factors. This article highlights the roles of cholecalciferol (vitamin D3) versus ergocalciferol (vitamin D2) supplementation for practicing pharmacists.

Cholecalciferol (D₃) Versus Ergocalciferol (D₂) in Older Adults.

Supplemental vitamin D is available in 2 distinct forms: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Pharmacopoeias have officially regarded these 2 forms as equivalent and interchangeable, yet this presumption of equivalence is based on studies of rickets prevention in infants conducted 70 y ago. The emergence of 25-hydroxyvitamin D as a measure of vitamin D status provides an objective, quantitative measure of the biological response to vitamin D administration. As a result, vitamin D3 has proven to be the more potent form of vitamin D in all primate species, including humans. Despite an emerging body of evidence suggesting several plausible explanations for the greater bioefficacy of vitamin D3, the form of vitamin D used in major preparations of prescriptions in North America is vitamin D2. The case that vitamin D2 should no longer be considered equivalent to vitamin D3 is based on differences in their efficacy at raising serum 25-hydroxyvitamin D, diminished binding of vitamin D2 metabolites to vitamin D binding protein in plasma, and a nonphysiologic metabolism and shorter shelf life of vitamin D2. Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification.

The case against ergocalciferol (vitamin D2) as a vitamin supplement.

Is vitamin D2 better than vitamin D3?

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].

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Vitamin D

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