Additional evidence that vitamin D eplains health disparities William B. Grant, Sunlight, Nutrition and Health Research Center 22 June 2015 Additional evidence that vitamin D helps explain black-white health disparities is found in these papers: Grant WB, Peiris AN. Possible role of serum 25-hydroxyvitamin D in Black¿White health disparities in the United States. J Am Med Directors Assoc. 2010 Nov;11(9):617-28. Grant WB, Peiris AN. Differences in vitamin D status may account for unexplained disparities in cancer survival rates between African and White Americans. Dermatoendocrinol. 2012;4(2):85-94. Recommended serum 25-hydroxyvitamin D concentrations for optimal health are at least 30 ng/ml and more likely above 40 ng/ml. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, 2011 Jul;96(7):1911-30. To reach these concentrations can take 1000-4000 IU/d vitamin D3. However, there is considerable variability in the relation of serum 25-hydroxyvitamin D to oral vitamin D intake: Garland CF, French CB, Baggerly LL, Heaney RP. Vitamin D supplement doses and serum 25-hydroxyvitamin D in the range associated with cancer prevention. Anticancer Res 2011;31:617-22. Thus, to be sure that optimal serum 25-hydroxyvitamin D concentrations are reached, testing may be useful. Competing interests I receive funding from Bio-Tech Pharmacal (Fayetteville, AR), and the Sunlight Research Forum (Veldhoven) and have received funding from the UV Foundation (McLean, VA), the Vitamin D Council (San Luis Obispo, CA), and the Vitamin D Society (Canada).