Vitamin D and Racial Disparity in Albuminuria: NHANES 2001-2006

BACKGROUND National data show unexplained racial disparity in albuminuria. We assessed whether low serum vitamin D status contributes to racial disparity in albuminuria. METHODS We examined the association between race and albuminuria (spot urinary albumin/creatinine ratio (ACR) >= 30) among non-Hispanic black and white nonpregnant adults who were free of renal impairment in the National Health and Nutrition Examination Survey (NHANES) from 2001-2006. We conducted analyses without and with serum 25(OH)D. We adjusted for age, sex, education level, smoking, body mass index (BMI), diabetes, diagnosis of hypertension, and use of antihypertensive medication. RESULTS Albuminuria was present in 10.0% of non-Hispanic blacks and 6.6% in non-Hispanic whites. Being black (odds ratio (OR) 1.46; 95% confidence interval (CI) 1.23-1.73) was independently associated with albuminuria. There was a graded, inverse association between 25(OH)D level and albuminuria. Notably, the association between race and albuminuria was no longer significant (OR 1.19; 95% CI 0.97-1.47) after accounting for participants' serum 25(OH)D. Similar results were observed when participants with macroalbuminuria (ACR >= 300 mg/g) or elevated parathyroid hormone (>74 pg/ml) were excluded or when a continuous measure of 25(OH)D was substituted for the categorical measure. There were no interactions between race and vitamin D status though racial disparity in albuminuria was observed among participants with the highest 25(OH)D levels. CONCLUSION Suboptimal vitamin D status may contribute to racial disparity in albuminuria. Randomized controlled trials are needed to determine whether supplementation with vitamin analogues reduces risk for albuminuria or reduce racial disparity in this outcome.