Diets higher in animal and plant protein are associated with lower adiposity and do not impair kidney function in US adults

Background: Higher-protein diets are associated with decreased adiposity and greater HDL cholesterol than lower protein diets. Whether these benefits can be attributed to a specific protein source (i.e., non-dairy animal, dairy, or plant) is unknown, and concerns remain regarding the impact of higher-protein diets on kidney function. Objective: The objective of this study was to evaluate trends of protein source on markers of cardiometabolic disease risk and kidney function in US adults. Design: Total, nondairy animal, dairy, and plant protein intake were estimated with the use of 24-h recall data from NHANES 2007-2010 (n = 11,111; >= 19 y). Associations between source-specific protein intake and health outcomes were determined with the use of models that adjusted for sex, race and ethnicity, age, physical activity, poverty to-income ratio, individual intake (grams per kilogram) for each of the other 2 protein sources, body mass index (BMI) (except for weight related variables), and macronutrient (carbohydrate, fiber, and total and saturated fat) intake. Results: Mean +/- SE total protein intake was 82.3 +/- 0.8 g/d (animal. 37.4 +/- 0.5 g/d; plant: 24.7 +/- 0.3 g/d; and dairy: 13.4 +/- 0.3 g/d). Both BMI and waist circumference were inversely associated [regression coefficient (95% CI)] with animal [-0.199 (-0.265, -0.134), P < 0.0001; -0.505 (-0.641, -0.370), P < 0.0001] and plant [-0.346 (-0.455, -0.237), P < 0.0001; -0.826 (-1.114, -0.538), P < 0.0001] protein intake. Blood urea nitrogen concentrations increased across deciles for animal [0.313 (0.248, 0.379), P < 0.0001; decile 1-10: 11.6 +/- 0.2 to 14.9 +/- 0.3 mg/dL] and dairy [0.195 (0.139, 0.251), P < 0.0001; decile 1-10: 12.7 +/- 0.2 to 13.9 +/- 0.2 mg/dL] but not plant protein intake. Glomerular filtration rate and blood creatinine were not associated with intake of any protein source. Conclusions: Diets higher in plant and animal protein, independent of other dietary factors, are associated with cardiometabolic benefits, particularly improved central adiposity, with no apparent impairment of kidney function.