Vitamin D

Vitamin D3 vs D2: Comparison of potency

This year, 2 studies concluded that vitamin D3 is more potent.

Study 1

  • Researchers at Creighton University, in Omaha, Nebraska, studied 33 healthy adults.
  • Calciferols were dosed at 50,000 IU/week for 12 weeks.
  • D3 was 87% more potent in raising and maintaining blood levels of 25(OH)D and produced 2- to 3-fold greater storage of vitamin D than D2.
  • The authors concluded, “Given its greater potency and lower cost, D3 should be the preferred treatment option when correcting vitamin D deficiency.”

Study 2

  • Researchers at the University of Wisconsin Osteoporosis Research Program, in Madison, studied 64 community dwelling older adults who were randomly assigned to receive daily (1,600 IU) or once-monthly (50,000 IU) D2 or D3 for 1 year.
  • D3 was slightly, but significantly, more effective than D2 for increasing blood levels of 25(OH)D.
  • The authors concluded, “1 year of D2 or D3 does not produce toxicity, and 25(OH)D levels of less than 30 ng/mL persisted in 20% of individuals.

The bottom line?

The greater response to vitamin D3 reported in these studies supports earlier results by researchers in Nebraska and South Carolina who concluded, “Vitamin D2 potency is less than one third that of vitamin D3.

“Physicians resorting to use of vitamin D2 should be aware of its markedly lower potency and shorter duration of action relative to vitamin D3.”

4/27/11 20:57 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.