Protein Food Label Requirement Disadvantages Plant-Based Protein, Scientists Argue in Current Developments in Nutrition

WASHINGTON, D.C.—U.S. and Canadian food labeling regulations require that protein digestibility be tested in rats to substantiate protein content claims for conventional foods. This requirement should be eliminated, scientists argue in a new article in Current Developments in Nutrition led by the Physicians Committee for Responsible Medicine, a medical ethics nonprofit.

To make a protein claim like “good source of protein,” foods are not evaluated on grams of protein alone. Rather, the percentage of the daily value of protein listed on food labels is adjusted based on protein tests that account for digestibility.

If digestibility data is unavailable, it must be developed by animal testing. This involves feeding the test diet to rats, collecting their waste, and measuring how much protein was absorbed.

This regulation disadvantages many plant-based foods in the marketplace, the authors argue, even as nutrition experts encourage higher intake of legumes, nuts, seeds, and other plant-based protein sources. Plant protein is harder to break down, in part due to its fiber content, making absorption lower compared to animal protein and causing it to have a lower score.

“Protein claims influence consumers’ choices at the point of purchase, but the current regulation makes it less likely they will choose plant-based protein sources,” says Anna Herby, DHSc, RD, CDE, co-author and nutrition education specialist at the Physicians Committee. “Evidence consistently shows that we should be eating more plant-based protein sources for long-term health.”

The animal test is at odds with consumer values, the paper says. It raises ethical concerns for consumers who avoid both animal-based foods and products tested on animals.

Protein quality testing for conventional foods does not meaningfully improve overall diet quality for most people. In high-income countries like the United States, protein intake usually meets or exceeds requirements for most people, including vegetarians and vegans.

“Protein deficiency is not a significant concern in North America, but too much saturated fat and too little fiber are,” Herby says. “Removing barriers to plant-based foods making protein claims can help align consumer choices with a dietary pattern that supports health and reduces risks of chronic disease, like cardiovascular disease and type 2 diabetes.”

For most people who already consume enough protein from varied sources, the amount of protein per serving is an appropriate basis for protein content claims.

The authors also highlight that other jurisdictions, including Australia and New Zealand, the European Union, and China and South Korea, rely solely on the amount of protein to substantiate protein claims, an approach they argue better aligns labeling regulations with current nutrition guidance and supports innovation in plant-based proteins.

Until the testing requirement is ended in the United States and Canada, how should protein quality be tested?  “In the current system where protein quality means digestibility testing, we should be using ethical methods—rather than defaulting to animal testing,” says Joseph Manuppello, lead author and a research analyst at the Physicians Committee. “Validated nonanimal, in vitro methods can assess protein digestibility—allowing regulatory requirements to be met without relying on animal testing where it does not add meaningful public health value.”

The Physicians Committee is working with partners through the U.S. Food and Drug Administration’s (FDA) qualification program to advance one such nonanimal method within the existing regulatory framework.

At a roundtable discussion convened by the Physicians Committee, participants identified this promising method, which is based on estimating digestibility by measuring the pH when protein is broken down by enzymes in vitro. This method is a leading candidate for regulatory qualification because of its history of use and agreement with in vivo results. After qualification, the article recommends that the regulation be updated to allow FDA to accept its results if digestibility data are unavailable, while also moving away from requiring digestibility measurement to support protein claims for conventional foods intended for adults and older children.