Advantages of Vitamin D3 over Vitamin D2

Cholecalciferol (vitamin D3) is a form of vitamin D of animal origin that is created from exposure to the sun, whereas ergocalciferol (vitamin D2) is of plant origin.

Glasses of milk

In Canada, milk is fortified with vitamin D3. This form of vitamin D is considered to be the most effective for achieving optimal vitamin D status.

  • According to a 2012 meta-analysis of randomized controlled trials that compared the effects of vitamin D3 and D2 supplementation, vitamin D3 is more efficacious than vitamin D2 at raising concentrations of serum 25-hydroxyvitamin D (an indicator of vitamin D status).1
  • Similar findings have been obtained from more recent randomized, placebo-controlled, trials. These studies have also found that vitamin D3 is more effective than vitamin D2 in increasing and maintaining higher serum concentrations of 25-hydroxyvitamin D.2,3 Furthermore, it has been demonstrated that vitamin D3 supplements may be more potent than vitamin D2 supplements in raising serum 25-hydroxyvitamin D levels in older adults as well as in maintaining these levels during the wintertime.4,5
  • Some studies have shown that daily administration or a loading dose of vitamin Dmay be equally as effective as vitamin D3 in raising and maintaining serum concentrations of 25-hydroxyvitamin D in the short term; however, in the long term, vitamin Dappears to better sustain these levels. 5-7   
  • Additionally, studies have shown that older adults who take 400 to 800 IU of vitamin D3 per day maintain their bone density and experience fewer fractures.8

Several mechanisms could explain the superior biological activity of vitamin D3 to that of vitamin D2. A plausible explanation is that vitamin D3 has a higher affinity for vitamin D binding protein as well as for the vitamin D receptor. It has also been suggested that vitamin D3 is the preferred substrate for the hydroxylase enzyme in the liver (which converts vitamin D to 25-hydroxyvitamin D).8 These are critical factors in the activation of vitamin D in the body. Moreover, vitamin Dmay have a shorter half-life than vitamin D3.9 

It should be noted that, in addition to its lower bioefficacy, vitamin D2 is considerably less stable than vitamin D3, particularly when in a crystalline powder form that is subjected to varying temperatures, humidity levels and even storage methods. Furthermore, there is a greater risk of toxicity with vitamin D2.8

Overall, given the scientific evidence on the superior bioavailability of vitamin D3 and its efficacy in terms of the treatment and prevention of vitamin D insufficiency, vitamin D3 may be the preferred form for food fortification.

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