A 1000 IU dose of vitamin D2 daily was as effective as 1000 IU vitamin D3 in maintaining serum 25-hydroxyvitamin D levels and did not negatively influence serum 25-hydroxyvitamin D3 levels. Therefore, vitamin D2 is equally as effective as vitamin D3 in maintaining 25-hydroxyvitamin D status.

Vitamin D(2) and vitamin D(3) are equally bioavailable in orange juice and capsules.

Vitamin D2 and vitamin D3 were effective in raising and maintaining total serum concentrations of 25(OH)D. Ingestion of vitamin D2 also resulted in an increase in serum concentrations of 1,25(OH)2D2. This increase was accompanied by a comparable decrease in serum concentrations of 1,25(OH)2D3; therefore, the total 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations did not significantly change after 11 weeks compared with baseline levels. Ingestion of vitamin D3 did not alter serum concentrations of 1,25(OH)2D3 or total 1,25(OH)2D. Therefore, ingestion of 1000 IU vitamin D2 or vitamin D3 for 11 weeks was effective in raising total serum concentrations of 25(OH)D as well as sustaining serum concentrations of total 1,25(OH)2D.