Associations of Diet with Albuminuria and Kidney Function Decline

Background and objectives: Sparse longitudinal data exist on how diet influences microalbuminuria and estimated GFR (eGFR) decline in people with well-preserved kidney function. Design, settings, participants, & measurements: Of the 3348 women participating in the Nurses' Health Study who had data on urinary albumin to creatinine ratio in 2000, 3296 also had data on eGFR change between 1989 and 2000. Cumulative average intake of nutrients over 14 years was derived from semiquantitative food frequency questionnaires answered in 1984, 1986, 1990, 1994, and 1998. Microalbuminuria presence and eGFR decline >= 30% were the outcomes of interest. Results: Compared with the lowest quartile, the highest quartile of animal fat (odds ratio (OR): 1.72; 95% confidence interval (CI): 1.12 to 2.64) and two or more servings of red meat per week (OR: 1.51; 95% CI: 1.01 to 2.26) were directly associated with microalbuminuria. After adjustment for other nutrients individually associated with eGFR decline >= 30%, only the highest quartile of sodium intake remained directly associated (OR: 1.52; 95% CI: 1.10 to 2.09), whereas beta-carotene appeared protective (OR: 0.62, 95% CI: 0.43 to 0.89). Results did not vary by diabetes status for microalbuminuria and eGFR outcomes or in those without hypertension at baseline for eGFR decline. No significant associations were seen for other types of protein, fat, vitamins, folate, fructose, or potassium. Conclusions: Higher dietary intake of animal fat and two or more servings per week of red meat may increase risk for microalbuminuria. Lower sodium and higher beta-carotene intake may reduce risk for eGFR decline. Clin J Am Soc Nephrol 5: 836-843, 2010. doi: 10.2215/CJN.08001109