Call to end rat digestibility tests for protein claims targets plant-based foods

US and Canadian food labeling regulations should be updated to eliminate the requirement to test protein digestibility in rats to substantiate protein content claims for conventional foods, according to a new peer-reviewed article.

The article, led by the Physicians Committee for Responsible Medicine and published in the journal Current Developments in Nutrition, argued that the existing regulatory framework places plant-based foods at a disadvantage, even as nutrition guidance increasingly encourages higher consumption of legumes, nuts, seeds, and other plant protein sources.

• A new article called for ending rat-based protein digestibility tests used to support protein claims on conventional foods in the US and Canada.

• The authors argued the requirement disadvantaged plant-based foods and raised ethical concerns related to animal testing.

• The article proposed replacing animal testing with validated in vitro methods or removing digestibility corrections altogether for most foods.

Under current US regulations, foods making protein claims such as “good source of protein” must report not only the total amount of protein per serving but also the percentage of the Recommended Daily Allowance provided. That percentage is calculated using protein values corrected for both amino acid composition and digestibility.

When digestibility data are unavailable, regulations require in vivo testing using rats.

The authors argued that this requirement disproportionately affects plant-based foods because many plant proteins are inherently less digestible than animal proteins. They noted that plant cell walls can limit access by digestive enzymes and that naturally occurring compounds such as antiproteases can interfere with protein breakdown.

At the same time, the article pointed out that cooking and other forms of processing can significantly improve the digestibility of plant proteins, complicating efforts to apply a single digestibility value across different food formats.

“Protein claims influence consumers’ choices at the point of purchase, but the current regulatory framework makes it less likely they will choose plant-based protein sources,” said Joseph Manuppello, lead author of the article and a research analyst at the Physicians Committee for Responsible Medicine. “It also raises ethical concerns for consumers who avoid both animal-based foods and products tested on animals.”

“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,” Manuppello added.

The article reported that replacing animal-based digestibility testing with validated in vitro methods could substantially reduce animal use. The authors noted that in Canada alone, thousands of foods with protein claims have entered the market in recent years, highlighting the scale of testing potentially involved.

At a roundtable discussion convened by the Physicians Committee, participants identified two in vitro methods they said showed promise. Both approaches estimate protein digestibility by measuring pH changes as proteins are broken down by enzymes in a controlled laboratory setting.

Because of its long history of use and agreement with in vivo results, the Physicians Committee said it planned to sponsor one such method through a US Food and Drug Administration qualification program.

The article recommended updating regulations to allow authorities to accept validated in vitro methods when digestibility data are unavailable, while moving away entirely from digestibility-based corrections for conventional foods intended for adults and older children.

“Protein deficiency is not a significant concern in North America, but diets high in saturated fat and low in fiber are,” said co-author Anna Herby, DHSc, RD, CDE, a nutrition education specialist at the Physicians Committee. “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.”

The authors also pointed to international precedents. They noted that regulators in Australia and New Zealand, the European Union, and China and South Korea primarily rely on total protein content to substantiate protein claims, rather than applying digestibility corrections.

According to the article, aligning US and Canadian labeling rules more closely with these approaches would better reflect current nutrition science while supporting innovation in plant-based protein products.