Environmental Impact of Protein Sources Ranked

As more consumers become aware of how their food choices affect the environment, demand for sustainably sourced foods is on the rise, but health remains an important consideration when choosing these foods.

So how does the average consumer weigh the nutritional quality and the environmental impact of a food? Until now, they couldn’t. But thanks to recently published research that included Carol Johnston, PhD, and Chris Wharton, PhD, both professors at Arizona State University’s College of Health Solutions, as authors, there now exists the basis for such a tool.

“This [study] is as much about consumers making choices right now as it is about the future of protein,” Wharton says. “Because this is one of the most important sustainability questions of our time.”

Hoping to address the growing conundrum, Wharton, Johnston, and colleagues built an algorithm to assign a score to some of the most commonly consumed protein-rich foods and rank them based on their efficiency at delivering the most protein at the smallest cost to the environment.

Protein values were calculated taking into account the protein’s bioavailability. Generally, protein from animal foods is easier to absorb than protein from plant foods because plant sources often are high in fiber that acts as a barrier to digestion.

Environmental impact was calculated through life cycle assessment analysis, which determines a food’s environmental impact by accounting for a variety of measures in the life cycle of a food product, from production to consumption to disposal.

Researchers focused on protein-rich foods because protein isn’t only one of the most important factors in a healthful diet but also where most resources go in terms of food production.

“There’s consensus developing now around how existential the climate crisis is,” Wharton says. “Central to that is our food production system, and then, vital to that is how we produce protein.”

What they found was foods such as peanuts and protein powders were most efficient at delivering protein with a small environmental cost, while cheeses, grains, and beef were least efficient.

“You can almost think about it like how you teach your kids what kinds of foods are ‘sometimes’ foods and what kinds of foods are ‘all-the-time’ foods, when it comes to fruits and veggies,” Wharton says. “We can do the exact same thing with proteins now. You can say, beef and white rice, these sorts of things are ‘sometimes’ foods; they’re indulgences. You have those once a week or less, maybe once a month. But peanuts and chicken and those sorts of things, you can eat those on a weekly basis. It helps people make those decisions.”

The fact that protein powders ranked so high in efficiency was surprising to the researchers, because they contain whey, an animal product.

But, Wharton reasons, that could be because there are two major contributors to environmental impact when it comes to protein-rich foods: on-farm contributors, such as crop fertilizers and gas emissions, and manufacturing contributors.

“So some of these products that are plant-based but require processing could end up having more of an environmental impact than you realize,” he says.

In the case of whey, its surprising ranking derives from a quirk in its life cycle assessment that attributes less environmental impact to dairy products than beef products.

Salmon and tuna also ranked high for efficiency, but only when they were wild caught.

“In our minds, we might think, ‘OK, animal proteins, probably bad for the environment. Plant proteins, probably good for the environment.’ But if you’re considering quality and environmental impact simultaneously, it’s not as clear cut,” Wharton says.

Researchers believe the rankings could be extremely useful for those who have tried to adopt vegetarian or vegan diets but failed.

“We have some other research that shows very few people striving to be vegetarian or vegan achieve it long-term,” Wharton says. “But maybe it doesn’t have to be so absolute. I kind of want to break the norm of absolutism in dietary choice and restriction. I think you could be plant-forward and eat beef only really rarely and eat tuna and salmon quite a bit more often and chicken here and there, and you’re achieving a diet that’s more sustainable and of high protein quality, maybe even more so than your standard vegetarian who’s totally committed.”

The rankings also could be useful when determining what kinds of foods to send in aid for those in need around the world.

“In the US, we have a lot of food,” Johnston says. “But if you go around the world, there’s a lot of protein malnutrition. And if you’re going to be feeding these billions of people outside the US, you can’t feed them something that isn’t sustainable.”

In addition, certain populations who are known to be protein deficient, such as the elderly and vegetarians, could benefit. Johnston and Wharton have pitched two studies to the USDA to pursue research along those lines.

“Right now, there’s just one recommended dietary allowance of protein for everybody,” Johnston says. “Regardless of whether you’re elderly, young, a vegetarian, or an omnivore.”

But previous research of hers found that vegetarians in particular should be consuming at least as much as 20% more than omnivores due to the low digestibility of protein from plant food sources.

This was a first-time collaboration for Johnston and Wharton, who specialize in vegetarian nutrition and food systems sustainability, respectively.

— Source: Arizona State University