People who eat more plant-based protein may live longer than those who get more protein from meat, a Japanese study suggests.

Researchers followed almost 71,000 middle-aged Japanese adults for an average of almost two decades. Compared to people who consumed the smallest amount of plant protein, participants who consumed the largest amount were 13 per cent less likely to die during the study and 16 per cent less likely to die of cardiovascular causes.

“Previous studies have found higher consumption of animal protein is associated with increased chronic diseases and mortality, whereas higher consumption of plant protein is associated with lower risk, but most of these studies were conducted in Western populations, in which consumption of animal protein is much higher than plant protein,” said Dr. Frank Hu, chair of the department of nutrition at the Harvard T.H. Chan School of Public Health in Boston.

“In this Japanese study, consumption of plant protein is quite high, whereas the consumption of animal protein is quite low compared to that in Western populations,” Hu, who wasn’t involved in the study, said by email.”

Animal protein didn’t appear to influence longevity in the study, researchers report in JAMA Internal Medicine.

Overall in the study, 12,381 people died, including 5,055 fatalities from cancer, 3,025 from cardiovascular disease, 1,528 from heart disease, and 1,198 due to cerebrovascular disease.

People who replaced just 3 per cent of red meat with plant protein were 34 per cent less likely to die of any cause, 39 per cent less likely to die of cancer, and 42 per cent less likely to die of heart disease during the study.

And, people who replaced just 4 per cent of processed meat in their diet with plant protein were 46 per cent less likely to die of any cause and 50 per cent less likely to die of cancer.

“When individuals eat more plant protein foods such as nuts, soy, and lentils, there is a significant improvement in cardiovascular risk factors such as blood lipids, blood pressure, and body weight,” Hu said.

“It is worth noting that these plant foods contain not just protein, but also other beneficial nutrients such as healthy fats, anti-oxidant vitamins, minerals, and phytochemicals,” Hu added. “On the other hand, diets high in red and processed meats have been associated with a wide range of health consequences such as diabetes, cardiovascular disease, and some cancers.”

The current study wasn’t a controlled experiment designed to prove whether or how the amount or type of protein people consume might directly impact their longevity.

One limitation of the research is that participants’ diets were only assessed once, at the start of the study, and it’s possible their eating habits changed over time, study coauthor Dr. Norie Sawada of the National Cancer Center in Tokyo and colleagues write in their report. Sawada didn’t respond to requests for comment.

“The take-home message is that to live longer, one should swap red and processed meat with healthy, plant proteins like nuts, beans, lentils, and whole grains,” Hu advised. “Such a dietary pattern is not only beneficial for human health but also more environmentally sustainable.”