Some vegetarians and vegans aren’t shy about touting the benefits of their diets, but new research suggests plant-based proteins may be most beneficial to those with more than one unhealthy habit.

Researchers from Massachusetts General Hospital, Harvard Medical School, and other research institutions, say proteins from plant sources are associated with a lower risk of death.

Interestingly, the protective effects of proteins from plant sources are especially helpful to people who smoke, drink, don’t exercise regularly, or are carrying around a few extra pounds.

Dr. Mingyang Song, Sc.D., a nutrition research fellow at Harvard, along with a team of researchers, published their findings today in JAMA Internal Medicine. They found eating more plant proteins, versus those from animal sources, may have protective benefits, especially for people with a vice or two.

So, say if someone is a smoker, even replacing a serving of bologna for a high-protein bean salad could have some measurable benefit?

“Yes, theoretically that is correct, although the magnitude of benefit will depend on the duration of the dietary replacement,” Song told Healthline.

The findings could help better direct nutrition guidelines for people who don’t always make the healthiest dietary and lifestyle choices.

The study concluded that substituting plant proteins for animal proteins — especially proteins from processed red meat — could make a difference in a person’s overall health.

Read more: The best proteins for your heart »

The oddly specific protective effects of plant proteins

To get their results, researchers used data from two studies that involved more than 131,000 health professionals, which included up to 32 years of follow-up. The surveys tracked men’s and women’s food intake through questionnaires and their health outcomes.

Overall, researchers found those who ate high levels of proteins from animals had a higher risk of dying younger.

Those who got their proteins from plants, however, fared better, but the results of the plant-based diets were most beneficial to people who smoked, drank at least 14 grams of alcohol a day, were overweight or obese, or were physically inactive. Also, getting proteins from plants helped people who were younger than 65 years of age, or older than 80, the most.

Researchers found substituting a mere 3 percent of calories from animal proteins for plant proteins lowered a person’s risk of death for all causes.

Specifically, the benefits of skipping processed red meat resulted in a 34 percent decrease in deaths. Cutting out unprocessed red meat resulted in a 12 percent decrease. And swapping out eggs for fruits or vegetables accounted for a 19 percent decrease.

Learn more: 19 protein-rich vegetables you should eat more of »

Why do plants offer more benefits to people with unhealthy habits?

“We do not know the exact mechanisms for this finding,” Song said.

Song did say there could be two interpretations of why vegetable proteins are so good for people with some unhealthy habits.

“First, people with bad habits are likely to already have some subclinical inflammatory or metabolic disorders, which may make them more sensitive to the beneficial effect of plant protein,” he said, adding it needs to be examined in future studies. “Second, given our observational design, the findings may be due to residual confounding by other lifestyle factors that we do not measure, or do not measure well in the current study.”

In other words, Song says, it is possible that other factors associated with high plant protein intake place people with unhealthy habits at lower risk for early death.

That doesn’t mean, however, people can continue on with unhealthy habits and think some vegetables can stave off the detrimental effects.

“Such harms significantly outweigh any beneficial effect they may get from high plant protein intake. Not to mention these people are also more susceptible to the negative effects of high animal protein intake,” Song said. “Therefore, taken together, maintaining a healthy lifestyle should still be a priority for long-term health benefits.”

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