Plant Versus Animal Protein Intake: Differences in Mortality

Recent debates have questioned the optimal macronutrient intake ratio, with some suggesting a high-protein diet is best—but it is uncertain what type of protein should be consumed. A study compared the long-term overall and cause-specific mortality between plant protein versus animal protein intake. The researchers concluded that plant protein was associated with a slightly lower risk for overall and cardiovascular-related mortality.

Data were collected on adults enrolled in the U.S. National Institutes of Health–AARP Diet and Health Study from 1995 to 2011. The primary outcome was hazard ratios (HRs) and 16-year absolute risk differences for overall and cause-specific mortality.

Final analysis included 237,036 men and 179,068 women. The median age was 62.2 years (standard deviation [SD], 5.4 years) for men and 62.0 years (5.4 years) for women. Over 6,009,748 person-years of observation, 77,614 deaths (18.7%) were assessed: 49,297 men and 28,317 women. When adjusting for clinical and other risk factors, greater dietary plant protein intake was correlated with reduced overall mortality in men (HR per 1 SD, 0.95; 95% confidence interval [CI], 0.94-0.97) and women (HR, 0.95; 95% CI, 0.93-0.96); the adjusted absolute risk differences per one SD were –0.36% (95% CI, –0.48% to –0.25%) and –0.33% (95% CI, –0.48% to –0.21%), respectively. For men, the HR per 10 g/1,000 kcal was 0.88 (95% CI, 0.84-0.91) and for women was 0.86 (95% CI, 0.82-0.90); adjusted absolute risk differences per 10 g/1,000 kcal were –0.95% (95% CI, –1.3% to –0.68%) and –0.86% (95% CI, –1.3% to –0.55%), respectively.

The correlation between plant protein intake and overall mortality was similar in subgroup analysis by smoking status, diabetes, fruit consumption, vitamin supplement use, and self-reported health status. Replacing 3% of energy from animal protein with plant protein was inversely correlated with overall mortality (10% decreased risk for both men and women) and cardiovascular disease mortality (11% decreased risk for men and 12% decreased risk for women); specifically, the reduced mortality was largely attributed to plant protein replacing egg protein (24% lower risk in men and 21% lower risk in women) and red meat protein (13% lower risk in men and 15% lower risk in women).

“Our findings provide evidence that dietary modification in choice of protein sources may influence health and longevity,” the authors concluded.