When plant milk started to gain traction in the mass market, the dairy industry fired back, claiming milk is a necessary protein source. This argument quickly crumpled, as soy milk has the same amount of protein (8 grams) as a glass of milk. To counter, dairy proponents are now claiming that proteins in milk are of “higher quality” than the protein in soy. We brought this to our team of scientists to take a closer look. Turns out the dairy industry is making false claims.
We specifically looked at a study published by the British Journal of Nutrition, cited on the Milk Life webpage, which suggests that cow’s milk proteins are far superior to plant-based protein, including protein from soy and peas. The study also claims that a protein’s quality is indicative of how easily it can be digested and used by our bodies. However, this is not entirely accurate.
Protein quality is only partially measured by its digestive properties. According to our analysis of several scientific research studies on protein quality (see references below), a more substantial factor in determining quality is the protein’s amino acid makeup, its ability to stimulate protein synthesis in the body, and its incorporation into skeletal muscles.
Using these factors, along with digestibility, we looked to the Protein Digestibility Corrected Amino Acid Score (PDCAAS) to weigh the true quality of plant-based milk in comparison to cow’s milk. The PDCAAS is a modern and reputable tool that measures protein quality; it is used by the World Health Organization and the Food and Agriculture Organization of the United Nations. According to this scale, both soy and cow’s milk proteins have an equal ranking of 1.0. However, upon further examination of the protein that make up cow’s milk, milk comes up short.
In a study that compared muscle protein synthesis between whey, casein, and soy protein, both whey and soy outperformed casein both pre- and post-exercise. As casein makes up 80 percent of the protein in cow’s milk, this result rattles the assumption that cow’s milk is superior to plant milk. In fact, it seems to be inferior based on these measurements.
The fact is, the vast majority of people don’t need to concern themselves with these intricate details. These numbers may help a top-level competitive athlete, but for the weekend warriors and those who just want to maintain a healthy and active lifestyle, protein quality should not be a major concern. Many medical professionals, such as Dr. James Loomis, Director of the Barnard Medical Center, assert that people can get enough protein simply by eating enough calories.
The dairy industry is attempting to create protein anxiety in a bid to promote cow’s milk and claw its way out of a dying business. It has hooked consumers for decades, looming over them with the fear of protein deficiency. But it is all smoke and mirrors perpetuated by creative data manipulation and well-funded marketing campaigns. In reality, there is no need to stress about protein. With a plant-based diet, people will get all the protein they need to optimize their health – no cow’s milk required.
To learn more about dairy-free proteins, read our plant-based protein guide.
Tang, J.E., D.R. Moore, G.W. Kujbida, M.A. Tarnopolsky and S.M. Phillips (2009) Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 107: 987-992.
Boye, J., R. Wijesinha-Bettoni, and B. Burlingame (2012) Protein quality evaluation twenty years after the introduction of the PDCAAS method. British Journal of Nutrition, 108: S183-S221.
Schaafsma, G. (2000) The Protein Digestibility–Corrected Amino Acid Score. Journal of Nutrition, 130: 1865S-1867S.