Danny Kim for TIME
August 1, 2016 11:00 AM EDT

There’s more evidence that a plant-based diet has a host of health benefits; it’s linked to a lower risk of heart disease, diabetes and certain cancers, and some studies even suggest it may help contribute to longevity.

Most of the evidence for this plant benefit focused on the beneficial fats found in plants. They’re generally unsaturated, and therefore they don’t tend to build up in heart vessel walls and cause problems. But in a new study published in JAMA Internal Medicine, researchers investigated whether the proteins in plants can have different effects on health than animal proteins, even apart from the effects that fats can have.

Dr. Mingyang Song from Massachusetts General Hospital and his colleagues analyzed data from two large ongoing studies: the Nurses Health Study and the Health Professionals Follow-Up Study, which involve more than 170,000 people who have been followed for an average of 28 years. Based on what the people reported they ate, Song and his team calculated the amount of protein they were receiving from animal and plant source and found that people who consumed more plant proteins had a lower risk of dying during the study than people who ate more animal proteins.

That’s not surprising, since previous studies have shown the benefits of a plant-based diet. But what surprised Song was the fact that the benefits seemed to be greatest among people who had at least one risk factor for early death, such as smoking, being overweight or obese, drinking alcohol or being physically inactive. That suggests that plant proteins may be offsetting some of the adverse effects that some risk factors may have on health.

In addition, the group found that the type of protein also matters. People who ate mostly a certain type of animal protein—from fish and chicken—had a lower mortality rate than those who ate more red and processed meat. In fact, while their death rates were still slightly higher than those who ate mostly plant proteins, they still were closer to the rates of plant-eaters than those who ate more red meat.

Song says the findings hint that the benefits of eating plant proteins may go beyond simply sparing the body the influx of vessel-clogging fats. So based on the findings, “if you have a choice between animal and plant protein, we would say plant protein is preferred and a better source,” he says. “But if people have to choose between different animal protein sources, then fish and chicken are probably better sources compared to processed red meat.”

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