Animal and plant protein usual intakes are not adversely associated with all-cause, cardiovascular disease–, or cancer-related mortality risk: an NHANES III analysis

We used data from NHANES 1988-1994 to examine associations between animal and plant protein usual intakes and IGF-1 concentration with mortality from all causes, cancer, and cardiovascular disease (CVD). Adult data (<i>N</i> = 15 937) were linked with mortality data (<i>N</i> = 3843 events) through 2006. Usual intakes for protein were estimated using the multivariate Markov Chain Monte Carlo method. Hazard ratio (HR) models were fit for mortality types (all-cause, cancer, and CVD) with protein intake measures (per 1 g increase) and IGF-1 concentration (<i>N</i> = 5753). There were no associations between animal protein (HR = 0.99; 95% confidence interval (CI): 0.98-1.01; <i>P</i> = 0.29) or plant protein (HR = 1.02; 95% CI: 0.95-1.10; <i>P</i> = 0.55) intake for all-cause mortality. Similar results were seen for CVD mortality and animal protein (HR = 1.02; 95% CI: 0.99-1.04; <i>P</i> = 0.14) and plant protein (HR = 1.01; 95% CI: 0.91-1.13; <i>P</i> = 0.81). There was an (inverse) association between cancer mortality and animal protein (HR = 0.95; 95% CI: 0.91-1.00; <i>P</i> = 0.04) but no relationship with plant protein (HR = 1.08; 95% CI: 0.93-1.24; <i>P</i> = 0.30). We found no association between concentrations of IGF-1 (<i>N</i> = 5753) for all-cause mortality (HR = 1.00; 95% CI: 0.99-1.00; <i>P</i> = 0.81), CVD mortality (HR = 0.99; 95% CI: 0.99-1.00; <i>P</i> = 0.53) or cancer mortality (HR = 1.00; 95% CI: 0.99-1.00; <i>P</i> = 0.76). Our results remained unchanged when the sample was separated into younger (<65 years) and older (>65, or between 50 and 65 years) cohorts. Our data do not support the thesis that source-specific protein intake is associated with greater mortality risk; however, animal protein may be mildly protective for cancer mortality. Mortality risk was not associated with circulating IGF-1 in any age group.