Dietary protein intake, kidney function, and survival in a nationally representative cohort

BACKGROUND: High-protein diets (e.g., Paleo, Atkins, South Beach, ketogenic) have gained popularity as a means to promote weight loss and avoid excess carbohydrate consumption. Yet in chronic kidney disease (CKD) patients, evidence suggests low dietary protein intake (DPI) leads to attenuation of kidney function decline, although concerns remain for risk of protein-energy wasting. OBJECTIVES: To examine associations of DPI with mortality in a nationally representative cohort of US adults, stratified by kidney function. METHODS: We examined the association between daily DPI scaled to actual body weight (ABW), ascertained by 24-h dietary recall, with all-cause mortality among 27,604 continuous NHANES adult participants (1999–2010), stratified according to impaired versus normal kidney function (estimated glomerular filtration rates <60 compared with ≥60 ml/min/1.72 m(2), respectively), using multivariable Cox models. We also examined the relation between high biological value (HBV) protein consumption with mortality. RESULTS: In participants with impaired kidney function, a high DPI of ≥1.4 g/kg ABW/day was associated with higher mortality, while lower DPI levels were not associated with mortality (reference, 0.6 to <1.0 g/kg ABW/day): the adjusted HRs (aHRs) were 1.09 (95% CI: 0.90, 1.32), 1.03 (95% CI: 0.82, 1.29), and 1.37 (95% CI: 1.02, 1.85) for DPI <0.6, 1.0 to <1.4, and ≥1.4 g/kg ABW/day, respectively. Yet in participants with normal kidney function, a low DPI of <0.6 g/kg ABW/day was associated with higher mortality, whereas higher DPI levels were not associated with death: the aHRs were 1.18 (95% CI: 1.04, 1.34), 0.92 (95% CI: 0.81, 1.04), and 0.99 (95% CI: 0.85, 1.16) for DPI <0.6, 1.0 to <1.4, and ≥1.4 g/kg ABW/day, respectively. The highest 2 tertiles of HBV consumption were associated with higher mortality in participants with impaired kidney function. CONCLUSIONS: Among participants with impaired kidney function, a higher DPI and greater HBV consumption were associated with higher mortality, whereas a lower DPI was associated with higher mortality in those with normal kidney function. Further studies are needed to elucidate the specific pathways between higher DPI and mortality in CKD