Weighing the benefits of plant protein for human and planetary health

November 18, 2022—While the proteins in animal products tend to be absorbed more easily than those from plant sources, that’s not a reason to choose beef over beans, according to Walter Willett, professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health.

In an October 31, 2022, Washington Post advice column, he wrote that the absorption difference is inconsequential for most Americans, who tend to consume more than enough protein to meet their needs. He also dismissed the idea that plant proteins are not “complete” and therefore people need to eat complementary foods such as rice and beans in the same meal.

“In fact, if we eat a variety of plant foods in our diet, the overall mix of amino acids isn’t substantially different from what we would get from eating animal protein,” he wrote.

Research by Willett and colleagues published in 2016 found that while the total amount of protein people consumed did not appear to impact how long they lived, high plant protein consumption was more positively associated with longevity than high animal protein consumption.

Shifting diets to be more plant-centric is also vital for the health of the planet, he wrote. For those who don’t want to completely give up animal products, Willett suggested sticking to about two servings a day—for example, a cup of yogurt and three or four ounces of chicken or fish—and adding more plant proteins and a diverse selection of fruits, vegetables, and whole grains.

Willett discussed dairy vs. plant milk in a November 15 CNN article. He and David Ludwig, professor in the Department of Nutrition, with whom he co-authored a 2020 review article, have found that dairy milk is not as beneficial for preventing bone fractures as previously thought, and may raise risk of some cancers if consumed in high amounts.

Another argument in favor of plant milk is that it takes far less land and water to farm crops like oats or soy compared to raising dairy cows, and produces far fewer greenhouse gas emissions.

“We need to look at everything we do from an environmental lens,” Willett said in the CNN article. “The answer isn’t just zero dairy for everybody, but three servings a day is not necessary for health and a disaster for the environment.”

Read the Washington Post article: Ask a Doctor: Is animal protein easier to absorb than plant protein?

Read the CNN article: Drink this type of milk to keep you and the planet healthy