Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality in a Japanese Cohort

Abstract

Importance: Epidemiological evidence regarding the long-term effects of higher dietary protein intake on mortality outcomes in the general population is not clear.

Objective: To evaluate the associations between animal and plant protein intake and all-cause and cause-specific mortality.

Design, setting, and participants: This prospective cohort study included 70 696 participants in the Japan Public Health Center-based Prospective Cohort who were aged 45 to 74 years and had no history of cancer, cerebrovascular disease, or ischemic heart disease at study baseline. Data were collected from January 1, 1995, through December 31, 1999, with follow-up completed December 31, 2016, during which 12 381 total deaths were documented. Dietary intake information was collected through a validated food frequency questionnaire and used to estimate protein intake in all participants. Participants were grouped into quintile categories based on their protein intake, expressed as a percentage of total energy. Data were analyzed from July 18, 2017, through April 10, 2019.

Main outcomes and measures: Hazard ratios (HRs) and 95% CIs for all-cause and cause-specific mortality were estimated using Cox proportional hazards regression models with adjustment for potential confounding factors.

Results: Among the 70 696 participants, 32 201 (45.5%) were men (mean [SD] age, 55.6 [7.6] years) and 38 495 (54.5%) were women (mean [SD] age, 55.8 [7.7] years). Intake of animal protein showed no clear association with total or cause-specific mortality. In contrast, intake of plant protein was associated with lower total mortality, with multivariable-adjusted HRs of 0.89 (95% CI, 0.83-0.95) for quintile 2; 0.88 (95% CI, 0.82-0.95) for quintile 3; 0.84 (95% CI, 0.77-0.92) for quintile 4; and 0.87 (95% CI, 0.78-0.96) for quintile 5, with quintile 1 as the reference category (P = .01 for trend). For cause-specific mortality, this association with plant protein intake was evident for cardiovascular disease (CVD)-related mortality (HRs, 0.84 [95% CI, 0.73-0.96] to 0.70 [95% CI, 0.59-0.83]; P = .002 for trend). Isocaloric substitution of 3% energy from plant protein for red meat protein was associated with lower total (HR, 0.66; 95% CI, 0.55-0.80), cancer-related (HR, 0.61; 95% CI, 0.45-0.82), and CVD-related (HR, 0.58; 95% CI, 0.39-0.86) mortality; substitution for processed meat protein was associated with lower total (HR, 0.54; 95% CI, 0.38-0.75) and cancer-related (HR, 0.50; 95% CI, 0.30-0.85) mortality.

Conclusions and relevance: In this large prospective study, higher plant protein intake was associated with lower total and CVD-related mortality. Although animal protein intake was not associated with mortality outcomes, replacement of red meat protein or processed meat protein with plant protein was associated with lower total, cancer-related, and CVD-related mortality.

Figure 1.. Hazard Ratios (HRs) for Mortality Associated With Isocaloric Substitution of 3% Energy From Plant Protein for Animal Protein From Various Sources

Model includes plant protein and the various sources of animal protein and is adjusted for total energy, percentage of energy from fats (saturated, monounsaturated, polyunsaturated, and other) and carbohydrates (all continuous), age (≤50, 51-55, 56-60, 61-65, 66-70, or >70 years), sex, body mass index (calculated as weight in kilograms divided by the height in meters squared; <22.5, 22.5 to <25.0, 25.0 to <27.5, or ≥27.5), smoking (never, past, or current with ≤20 or >20 cigarettes per day), alcohol use (none or occasional or regular ethanol consumption of <150, 150 to <300, or ≥300 g per day), physical activity (quartile category in metabolic equivalent hours per day), occupation status (agriculture/forestry/fishery, salaried/professional, self-employed, housework/unemployed, or other), and intake of green tea (never, <1, 1, 2-3, or ≥4 cups per day) and coffee (never, <1, 1, or ≥2 cups per day).

Figure 2.. Hazard Ratios (HRs) for Mortality Associated With Isocaloric Substitution of 3% Energy From Fish Protein for Other Animal Protein Sources

Model includes animal protein from various sources and plant protein and is adjusted for total energy, percentage of energy from fats (saturated, monounsaturated, polyunsaturated, and other) and carbohydrates (all continuous), age (≤50, 51-55, 56-60, 61-65, 66-70, or >70 years), sex, body mass index (calculated as weight in kilograms divided by the height in meters squared; <22.5, 22.5 to <25.0, 25.0 to <27.5, or ≥27.5), smoking (never, past, or current with ≤20 and >20 cigarettes per day), alcohol use (none or occasional or regular consumption of ethanol of <150, 150 to <300, or ≥300 g per day), physical activity (quartile category in metabolic equivalent hours per day), occupation status (agriculture/forestry/fishery, salaried/professional, self-employed, housework/unemployed, or other) and intake of green tea (never, <1, 1, 2-3, or ≥4 cups per day) and coffee (never, <1, 1, or ≥2 cups per day).