Total, animal, and plant protein intake and pneumonia mortality in the Japan Public Health Center-based Prospective Study

Abstract

Background: The association between total protein intake and all-cause mortality is inconsistent. Pneumonia is a major cause of death among the elderly, and the association between protein intake and pneumonia mortality warrants clarification.

Objectives: We aimed to examine the association between total, plant, and animal protein intake and pneumonia mortality in a prospective design.

Methods: The Japan Public Health Center (JPHC)-based Prospective Study prospectively follows 83,351 participants (37,652 men and 45,699 women). Total, plant, and animal protein intakes were calculated from a validated food-frequency questionnaire. A Cox hazards model was used to calculate HRs and 95% CIs, with adjustment for confounding factors.

Results: During ∼18.4 y of follow-up, 990 pneumonia deaths (634 men and 356 women) were observed. In the multivariable-adjusted model and in the model further adjusted for fatty acid intake, increase in total protein intake was marginally significantly associated with lower pneumonia mortality in women [lowest vs. highest quartile, HR (95% CI): 0.71 (0.53, 0.97), P-trend = 0.01 in the multivariable-adjusted model, and 0.70 (0.45, 1.06), P-trend = 0.05 in the fatty acid intake-adjusted model]. Total protein intake in men and animal and plant protein intake in both men and women were not significantly associated with pneumonia mortality in the fatty acid-adjusted model.

Conclusions: Although the HR in the highest quartile was not significant and further research to determine the upper limit of recommended protein intake is required, higher total protein intake was associated with lower pneumonia mortality in women.

Keywords: Japanese; mortality; pneumonia; prospective study; protein intake.