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Providing perspectives on recent research into vitamins and nutritionals


Vitamin D Supplementation and Health

By Michael McBurney

A colleague of mine, Dr Jane Doe, recently expressed an opinion that vitamin D supplementation is ineffective in raising serum 25(OH)D3 concentrations. Because I respect Jane, her apparent dismissal of the evidence stymied me.

Dear Jane, I hope you saw the paper by Curiel-Lewandrowski and colleagues. High-dose vitamin D supplementation (50,000 IU D3 twice weekly for 8-9 weeks) significantly increased serum 25(OH)D3 concentrations in adults from 21.6 ng/mL (53 nmol/L) to 70.5 ng/mL (177 nmol/L).  There were no adverse effects.

The authors considered serum 25(OH)D3 concentrations < 30 ng/mL (75 nmol/L) as vitamin D insufficient which differs from the Institute of Medicine definition of <20 ng/mL (50 nmol/L). The study goal was to identify biomarkers of vitamin D bioactivity in the skin, including skin with moderate-to-severe sun photodamage. Cytochrome P 450 24 (CYP24) mRNA expression in skin is sensitive to solar exposure and photodamage. CYP24 mRNA responded to vitamin D status and may be a useful biomarker of skin differentiation. My point, Jane, is vitamin D supplementation increases serum 25(OH)D3 concentrations.

Vitamin D3 (cholecalciferol) more effectively increases serum 25-hydroxyvitamin D concentrations than vitamin D2 (ergocalciferol) but let’s be clear; either form will increase vitamin D status. Total 25-hydroxyvitamin D is the sum of metabolites of cholecalciferol and ergocalciferol. Claims that vitamin D2 and D3 are identical are the result of ‘apples and oranges’ comparisons.

Polymorphisms in vitamin D binding protein (VDBP) may partially account for ethnic differences. But do not be deterred. Bischoff-Ferrari and colleagues clearly demonstrate the health benefits of maintaining serum 25(OH)D concentrations above 50, and preferably 75 nmol/L.

Your friend and colleague, Michael

Main Citation

Curiel-Lewandrowski C, Tang JY, Einspahr JG, Bermudez Y, Hsu CH, Rezaee M, Lee Ah, Tangrea J, Parnes HL, Alberts DA, Chow H-HS. Pilot study on the bioactivity of vitamin D in the skin after oral supplementation. 2015 Cancer Prev Res doi: 10.1158/1940-6207.CAPR-14-0280

Other Citations

Heaney RP, Recker RR, Grote J, Horst RL, Armas LAG. Vitamin D3 is more potent than vitamin D2 in humans. 2010 JCEM doi: 10.1210/jc.2010-2230

Carter GD, Phinney KW. Assessing vitamin D status: Time for a rethink? 2013 Clin Chem doi: 10.1373/clinchem.2013.219386

Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, Dawson-Hughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. 2006 Am J Clin Nutr 84:18-28