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Kidney Cancer differences with skin color probably due to vitamin D differences – May 2015

Differences in 25-Hydroxyvitamin D Concentrations May Explain the Black-White Differences

in Chronic Kidney Disease and Risk of Renal Cell Carcinoma
Epidemiology • Volume XX, Number XXX, XXX 2015

To the Editor:

The recent article by Hofmann and colleagues1 reported increased association of chronic kidney disease with renal cell carcinoma for blacks, Asians, and Hispanics, but not whites. The black-white disparity for renal cell carcinoma incidence for blacks was attributed to hypertension and chronic kidney disease. The authors recommended additional studies to evaluate the possible factors underlying the association between chronic kidney disease and risk of renal cell carcinoma. This letter outlines the evidence that racial differences in 25-hydroxyvitamin D [25(OH)D] concentrations may explain the findings.

Due to dark skin pigmentation and the fact that most vitamin D is produced in the skin through ultraviolet-B exposure, black Americans have lower 25(OH)D concentrations than white Americans.2,3 A study based on data from the Third National Health and Nutrition Examination Survey- linked Medicare claims files found that, over a 9.1-year follow-up, non-Hispanic blacks individuals “had a 2.83-fold (95% confidence interval [CI] = 1.03, 7.77) higher risk for developing (end- stage renal disease) compared with non-Hispanic white individuals. Additional adjustment for 25(OH)D levels reduced the risk by 58% (incidence rate ratio 1.77; 95% CI = 0.38, 8.21).”2

Another study using data from the same survey found a multifactor adjusted black-white systolic blood pressure difference of 4.0 mmHg; adding 25(OH) D concentration reduced the race difference to 2.9 mmHg, which was increased to 4.0 mmHg when those on antihypertensive medications were excluded. 3 Low 25(OH)D concentrations are also a risk factor for renal cell carcinoma. Blood was drawn at time of enrollment and people were enrolled between 1992 and 2000 and followed up to December 2004 to June 2010 depending on the country. The odds ratio for a doubling of 25(OH)D concentration was 0.82 (95% CI = 0.68, 0.99).4 While no results are presented for Hispanics, the finding in Ref. 1 that their risk of renal cell carcinoma with respect to hypertension and chronic kidney disease is intermediate between that for blacks and whites is consistent with the fact that they have mean 25(OH)D concentrations intermediate between blacks and whites due to having skin pigmentation intermediate between the two races.

William B. Grant
Sunlight, Nutrition, and Health Research Center San Francisco, CA wbgrant at infionline.net

REFERENCES

  • Hofmann JN, Corley DA, Zhao WK, et al. Chronic kidney disease and risk of renal cell carcinoma: differences by race. Epidemiology. 2015;26:59-67.
  • Melamed ML, Astor B, Michos ED, Hostetter TH, Powe NR, Muntner P. 25-hydroxyvitamin D levels, race, and the progression of kidney disease. J Am Soc Nephrol. 2009;20:2631- 2639.
  • Fiscella K, Winters P, Tancredi D, Franks P. Racial disparity in blood pressure: is vitamin D a factor? J Gen Intern Med. 20n;26:1105-1m.
  • Muller DC, Fanidi A, Midttun 0, et al. Circulating 25-hydroxyvitamin D3 in relation to renal cell carcinoma incidence and survival in the EPIC cohort. Am J Epidemiol. 2014;180:810-820.

See also VitaminDWiki

The articles in Mortality and Darker Skin are here:

The items in both Kidney and Darker skin categories in VitaminDWiki are:

Black Disparity 16 vs 26 ng/ml
breast cancer 1.34 1.26
colorectal cancer 1.43 1.44
cardiovascular disease1.29 1.27
all-cause mortality 1.26 1.26

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