by Dr. Mercola

According to a new study, vitamin D3 is 87 percent more potent at raising vitamin D blood levels than vitamin D2.  Vitamin D3 also produces a 2- to 3-fold increase over D2 in the storage of the vitamin.

Scientists gave 33 healthy adults 50,000 International Units (IU) of either vitamin D2 or D3 each week for a total of 12 weeks. About 17 percent of the D3 ingested was stored by the subjects, and the rest was consumed or metabolized.

According to the study in the Journal of Clinical Endocrinology & Metabolism:

“Given its greater potency and lower cost, D3 should be the preferred treatment option when correcting vitamin D deficiency.”

Article link: http://articles.mercola.com/sites/vitalvotes/archive/2011/01/24/warning-if-you-supplement-with-vitamin-d-use-the-form-that-is-ten-times-stronger.aspx