Association of dietary protein intake and microalbuminuria in healthy adults: Third National Health and Nutrition Examination Survey

Background: The relationship between dietary protein intake (DPI) and microalbuminuria (MA) is unclear. We investigated whether DPI was associated with urinary albumin level in a population sample of persons with normal kidney function. Methods: We addressed this question in adults aged 20 to 80 years from the Third National Health and Nutrition Examination Survey (n = 12,422). DPI was assessed from a 24-hour dietary recall and quantified as percentage of total energy intake. MA is defined as urinary albumin-creatinine ratio 30 mg/g (3 mg/mmol) or greater. Results: In multivariable logistic regression models adjusted for sociodemographic characteristics and coronary heart disease risk factors, DPI was not associated with MA in normotensive or nondiabetic persons. In crude models, odds ratios (ORs) for MA were 1.9 (95% confidence interval, 1.2 to 3.0) in persons with hypertension (n = 3,433) and 2.4 (95% confidence interval, 1.1 to 5.2) in those with diabetes (n = 1,165) in the highest (>19%) versus lowest (<11.7%) quintile of DPI. However, in models adjusted for the concurrent prevalence of diabetes or hypertension, this association attenuated to nonsignificance. Persons in the highest quintile of DPI who had both hypertension and diabetes (n = 634) had a significantly elevated OR for MA (3.3; 95% confidence interval, 1.4 to 7.8) compared with those in the lowest quintile. Conclusion: DPI is not associated with MA in healthy persons or those with isolated hypertension or diabetes. However, in persons with both conditions, high DPI is associated with increased prevalence of MA. These findings suggest the need for further research on weight-loss strategies for high-risk persons.