Effect of Iso-Caloric Substitution of Animal Protein for Other Macro Nutrients on Risk of Overall, Cardiovascular and Cancer Mortality: Prospective Evaluation in EPIC-Heidelberg Cohort and Systematic Review

Ecological studies showed correlations between a shift toward animal-protein-rich diets and longer life-expectancy; however, only a few studies examined individual-level association of protein source and mortality risks using appropriate iso-caloric substitution models adjusted for total energy intake. We used EPIC-Heidelberg (European Prospective Investigation into Cancer and nutrition) to create iso-caloric substitution models and determined relative all-cause, cardiovascular and cancer mortality hazards associated with dietary intake of animal protein and other macronutrients, employing Cox proportional hazard models. For comparison with other studies, we also synthesized evidence from a systematic review relating animal protein intake to mortality risk from seven prospective cohort studies in the USA, Europe and Japan. Substitution of 3% of total energy from animal protein for fat (saturated, mono-unsaturated) and carbohydrate (simple, complex) was associated with all-cause mortality (Hazard Ratios [HR] from 1.05 to 1.11), mostly driven by cardiovascular mortality (HR from 1.13 to 1.15). Independently of animal protein, substituting poly-unsaturated fat for saturated fat increased cancer-related mortality risk by 12 percent. The systematic review largely corroborated our findings. Overall, higher proportions of dietary energy from animal protein, combined with low energy intake from either carbohydrate sub-types or dietary fats, increases all-cause and cardiovascular mortality risks, but not cancer-related mortality.