Plant-based burgers often promise an amount of protein comparable to their animal-based counterparts, but not all sources of proteins are equal. Rather the body depends on essential amino acids, the concentration and digestibility of which differ among protein sources.
To account for these differences, a new standard for protein quality, the digestible indispensable amino acid score (DIAAS), was developed by the U.N.’s Food and Agriculture Organization (FAO), which specifically focusses on the digestibility of essential amino acids.
A new study, published in the European Journal of Nutrition, used the DIAAS system to compare protein quality in meat-based and plant-based burgers.
The researchers fed the pigs (the recommended test animal) with patties alone for pork burgers, 80% and 93% lean beef burgers, the soy-based Impossible Burger, and pea-based Beyond Burger. They then measured digestibility of individual essential amino acids, computing DIAAS values from those scores.
Both beef and pork burgers scored as “excellent” sources of protein (DIAAS scores 100+, for people of all ages). The Impossible Burger also scored as an excellent protein source for ages 3 and up, but not under 3. Beyond Burger scored 83, a “good” source of protein for ages 3 and up.
“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 Hans H. Stein, professor in the Department of Animal Sciences and the Division of Nutritional Sciences at Illinois and co-author on the European Journal of Nutrition study.
Since burger patties are usually eaten with a bun, the researchers looked at the impact of adding the low-protein bun and as expected, it reduced DIAAS values.
Consuming the Impossible Burger together with a bun reduced the DIAAS value to “good” for ages 3 and up. But when pork or 80% lean beef patties were consumed together with buns, DIAAS values were still at or above 100 for the over-3 age group, demonstrating that the needs for all essential amino acids were met by these combinations.
“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-3 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 as if you eat the pork-based or the beef-based burgers. And if you have to eat more, that means you also get more calories,” said co-author Mahesh Narayanan Nair, professor at Colorado State University.
Stein said, “It’s particularly children, teenagers, lactating women, and older people who are at risk of not getting enough amino acids. 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.”
