Study Examines Health Effects of Animal and Plant Protein

Deciding between grilled steaks or your famous vegetarian five-bean chili for dinner? Go with the chili. Research has found people who eat more protein from plants may live longer—even when they have a health risk factor, like obesity or a smoking habit. The study was published in JAMA Internal Medicine and looked at data from 131,342 participants, age 49 or older, from the Nurses’ Health Study (1980 to 2012) and the Health Professionals Follow-up Study (1986 to 2012). At the beginning of both studies and every two years until the end of both studies, the participants answered questionnaires regarding their lifestyle and medical history, which researchers assessed for unhealthy lifestyle factors including smoking, heavy drinking, high body mass index, and physical inactivity. In addition, participants filled out food questionnaires every four years, in which they answered how often, on average, they had eaten a standard portion of animal protein (processed and unprocessed red meat, poultry, eggs, fish, and dairy) and plant protein (beans, lentils, soy, nuts and seeds, and whole grains). Researchers looked at death records to identify total deaths, and the causes of those deaths, during the duration of both studies. They discovered that:

  • Each 3% increase in calories from plant protein was associated with a 10% lower risk of death from any cause.
  • Each 10% increase in calories from animal protein was associated with an 8% higher risk of death, particularly from cardiovascular disease.
  • In people with diabetes, the negative effects of animal protein and the positive effects of plant protein were stronger.
  • A second analysis of the data showed that the effects of different protein sources were only experienced by people with at least one unhealthy habit—smoking, physical inactivity, or heavy alcohol intake—or who were overweight or obese. In people with none of these factors, protein source did not appear to affect risk of death.
  • Based on their findings, the researchers determined that, overall, replacing 3% of calories from animal protein with plant protein would lower the risk of death from any cause. Specifically, replacing protein from processed red meat with plant protein would lower the risk by 34%; replacing protein from unprocessed red meat with plant protein would lower the risk by 12%; and replacing protein from eggs with plant protein would lower the risk by 19%. Smaller benefits would be expected from replacing protein from poultry, dairy products, and fish with plant protein.

Does this mean we all need to become strict vegans? Not necessarily. While vegan and vegetarian diets have been associated with better heart health, lower risk of certain cancers, and lower risk of death from all causes, this study’s findings show that even incremental change—that is, eating more plant protein and replacing some meat protein with plant protein—can have a meaningful positive impact on health. So, while you can still have grilled steaks for dinner once in a while, you may also want to eat more meals with beans, whole wheat pasta, and nuts.

Source: JAMA Internal Medicine

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