Vitamin D2 supplements may reduce vitamin D3 levels

Researchers have identified that taking vitamin D2 supplements may unexpectedly reduce levels of vitamin D3 in the blood. A meta-analysis of previous scientific studies conducted by the University of Surrey found that participants taking vitamin D2 had significantly lower concentrations of 25-hydroxyvitamin D3 compared to those not receiving D2.

While both D2 (ergocalciferol) and D3 (cholecalciferol) can increase overall vitamin D status, D3 is generally more effective at raising and maintaining the specific form of the vitamin measured in blood tests. Vitamin D is critical for calcium absorption, bone health, muscle function, and immune system regulation.

One potential explanation for this phenomenon is that increased levels of D2 might accelerate the breakdown and clearance of metabolites derived from D3. Although D2 still contributes to vitamin D sufficiency, the distinction is important as D3 is the form naturally produced by human skin through sunlight exposure.