Researchers have found that vitamin D2 is equally as effective as vitamin D3 in maintaining 25-hydroxyvitamin D status. Vitamin D2 has been the main stay for the prevention and treatment of vitamin D deficiency in children and adults and as little as 100 IU of vitamin D2 was found to be effective in the prevention of rickets. Both vitamin D2 and vitamin D3 form 25-hydroxyvitamin D.