A US study funded by the Beef Checkoff and the National Pork Checkoff claims that there are fewer digestible amino acids in plant-based Impossible and Beyond Meat burgers than in pork or beef versions. Therefore, it suggests that the way that protein is expressed on current nutrition labels – a single generic value expressed in grams – can be misleading.

The outcomes were leveraged against the UN’s Food and Agriculture Organization (FAO) digestible indispensable amino acid score (DIAAS).

Both beef and pork burgers, served without buns, scored as “excellent” sources of protein. The Impossible Burger, when served without a bun, scored as “an excellent protein source” for ages three years and older but not for children less than three years.

With a value of 83, the bunless Beyond Burger was a “good” source of protein for ages three and older.

“It’s particularly children, teenagers, lactating women and older people who are at risk of not getting enough amino acids, says Hans Stein, professor at the Department of Animal Sciences and the Division of Nutritional Sciences at Illinois and co-author on the European Journal of Nutrition study.

“Results of this experiment, along with previous data, demonstrate the importance of getting animal-based proteins into diets to provide sufficient quantities of digestible essential amino acids to these populations,” he underscores. 

DIAAS values
The experiment revealed that there was a greater DIAAS value of mixing either the pork or beef burger with the bun – values of 107 and 105 respectively, for the over-three age group – than there was for the Impossible Burger, which had a DIAAS value of 86 if consumed with the bun. 

“That means you need to eat 15% more of the Impossible Burger-bun combination to get the same amount of digestible amino acids than when you eat the pork-based or the beef-based burgers. And if you have to eat more, that means you also get more calories,” says Mahesh Narayanan Nair, professor at Colorado State University and a co-author of the publication.The study leverages the DIAAS system to understand protein quality in beef and pork burgers and plant-based burgers.

Animal-based proteins aid brain development
An adequate intake of amino acids is really important in developing countries wher there may be little access to animal-based proteins, particularly for children. In some countries, a majority of children are amino acid deprived. 

“That’s extremely serious because, if children dont get enough amino acids, their brain development can suffer. It’s especially important in those cases to design a strategy for getting high-quality proteins into diets for children,” explains Stein.

Plant-based burgers often promise protein comparable to their animal-based counterparts, but the way protein is expressed on current nutrition labels – a single generic value expressed in grams – can be misleading because the human body does not use “protein” per se.

Instead, it needs essential amino acids, which are present in proteins, but the concentration and digestibility of amino acids are different among protein sources.

To account for these differences, a new standard for protein quality, the DIASS score was developed a decade ago. It focuses on the digestibility of essential amino acids and aims to put more accurate tools in the hands of nutritionists and food assistance programs worldwide.

The study leverages the DIAAS system to understand protein quality in beef and pork burgers and plant-based burgers from Impossible and Beyond Meat.

Plant-based versus meat experiment
Researchers fed 80% pork burgers and 93% lean beef burgers, the soy-based Impossible Burger and pea-based Beyond Burger to pigs, the FAO’s recommended research subject for DIASS studies.

They measured the digestibility of individual essential amino acids and used those digestibility scores to compute DIAAS values.

“We have previously observed that animal proteins have greater DIAAS values than plant-based proteins and that is also what we observed in this experiment,” says Stein.

Burger patties are typically eaten with a bun, so the researchers also looked at the protein quality of patties and buns together. Because grain products, like hamburger buns, offer low protein quality, feeding the bun and the patties together reduces DIAAS values, they conclude.