Lower intake of dietary protein in midlife was a significant independent predictor of all-cause mortality in later life, based on data from a cohort study of more than 8000 men.
The Recommended Dietary Allowance of dietary protein intake is 0.8 g/kg body weight, but previous studies of the effect of dietary protein on all-cause mortality have yielded inconsistent results, Pedro Joaquin Ayau Aguilar, MD, of the University of Hawaii, Honolulu, said in a presentation at the annual meeting of the American Geriatrics Society.
To better examine these effects, Dr. Aguilar and colleagues reviewed data from 7486 participants in the Kuakini Honolulu Heart Program (HHP), a prospective cohort study of Japanese-American men in Hawaii.
Participants underwent a baseline exam in 1965-1968 at ages 45-68 years and were followed for mortality until December 31, 2022. The researchers created quintiles of dietary protein/kg categorized as plant or animal source, trained dietitians worked with participants to complete a 24-hour diet recall, and the primary outcome was all-cause mortality.
Overall, the mean protein intake in the study population was 1.5 g/kg body weight; the mean animal protein and plant protein intakes were 1.1 g/kg and 0.4 g/kg, respectively.
In an age-adjusted analysis, mortality rates per 1,000 person-years were significantly higher with lower total protein intake, with rates of 39.7 per 1,000 person-years and 36.8 per 1,000 person-years in the first and fifth quintiles, respectively (P < .0001).
Data Show Consistency Across Protein Types
Trends were similar for animal protein and plant protein intake, with mortality rates of 39.6 and 36.5 per 1000 person-years for the first and fifth quintiles, respectively.
“All of these categories had a significant trend, with the lowest quintile showing the highest mortality rate,” Dr. Aguilar said in his presentation.
The study was limited by several factors including the homogeneous population of Japanese men, and the inability to make conclusions about cause and effect, Dr. Aguilar said. However, the results were strengthened by the large cohort, long follow-up, and complete mortality surveillance, he added.
As for the study’s clinical implications, “I believe it adds to the body of evidence on how nutrition impacts health and [the data] can help us better advise our patients on their macronutrient intake to better optimize their health,” Dr. Aguilar said in a question-and-answer session following the presentation.
Looking ahead, “More research is needed to more accurately define which type of protein and in which amounts are optimal for health,” as well as how other macronutrients in different stages of life affect health span and life span, he said.
Although a minimum Recommended Daily Allowance of dietary protein is 0.8 g/kg body weight, the relationship between dietary protein intake and all-cause mortality remains unclear, said Shelly Gray, PharmD, professor of pharmacy at the University of Washington School of Pharmacy, said in an interview.
Dr. Gray, who served as a moderator for the session in which the study was presented, agreed that more research is needed before clinical implications can be discussed.
The study was supported by the Department of Geriatric Medicine, John A. Burns School of Medicine, University of Hawaii; Kuakini Medical Center, Honolulu, Hawaii; and the National Institutes of Health. The researchers had no financial conflicts to disclose. Dr. Gray had no financial conflicts to disclose.