The popularity of plant-based diets is increasing, with it the demand for plant-based protein sources. A recent study  compared three plant-based protein blends to a whey protein supplement, looking at the appearance of the essential amino acids in the blood of their participants. If you imagine a brick wall being the complete protein source, the bricks are the different amino acids which make up that protein. Animal-based proteins have previously been the most popular form of protein powders, generally for their higher availability and taste, but also because of their efficacy over plant-based alternatives . This is usually down to their increased content of the amino acid leucine, a potent stimulant for muscle protein synthesis (MPS).
When a complete protein is digested, it’s broken down into its ingredients which are then transported around the body in the blood. To investigate how much of the complete protein is broken down and therefore available to be used by the muscle, scientists measure the amount of these amino acids that appear in the blood after digestion. The size of this blood amino acid response provides insight into the potential muscle protein response following digestion.
In this experiment, scientists took healthy, adult men with a history of resistance training. They randomly assigned these men into groups, and each participant received each supplement through the study in random order. The supplements were a whey protein, and the three plant-based supplements contained different combinations of pea, pumpkin, sunflower and coconut protein. Interestingly, all supplements were matched for leucine content at 2.6 grams, meaning the amount of leucine appearing in the blood after digestion should be the same. Furthermore, each protein scored the same (1.0) on the Protein Digestibility Corrected Amino Acid Score (PDCAAS), meaning each supplement was scored the same for the quality of its amino acids and the human ability to digest it . All of this suggests that the supplements should have performed quite similarly in the analyses.
What the scientists observed was a similar increase in blood amino acids between all three plant-based blends. However, there was a significantly higher (30-40%) response for the whey protein powder (see below). This included the amount of leucine appearing in the blood. That said, the plant-based protein blends caused an approximate two-fold increase. Despite these results, the study did not measure the muscle protein synthesis response. So, from this study at least, it isn’t possible to say whether there was any difference (in the MPS response) between the supplements.
Plant-based protein blends have certainly come along way over the last few years and provide a safe alternative to dairy-based supplements. Whilst this study showed that plant-based blends may not be absorbed as efficiently as whey protein, these blends were still absorbed with good efficiency. Furthermore, from this study, we cannot conclude whether plant-based proteins are any less effective than whey protein in stimulating muscle protein synthesis when matched for leucine content. If you are considering buying a protein supplement and want the best bang for buck, dairy-based proteins are still the first recommendation. However, this study demonstrates that plant-based supplements can still be an effective way of increasing the protein content of your diet.
- Brennan, J,L, Keerati-U-Rai, M, Yin, H, Daoust, J, Nonnotte, E, Quinquis, L, St-Denis, T, Bolster, D.R. (2019). Differential Responses of Blood Essential Amino Acid Levels Following Ingestion of High-Quality Plant-Based Protein Blends Compared to Whey Protein-A Double-Blind Randomized, Cross-Over, Clinical Trial.Nutrients 6;11(12)
- Van Vliet, S.; Burd, N.A.; van Loon, L.J. (2015). The skeletal muscle anabolic response to plant-versus animal-based protein consumption. J. Nutr, 145, 1981–1991.
- FAO Food and Agriculture Organization of the United Nations/World Health Organization. Protein Quality Evaluation: Report of the Joint FAO/WHO Expert Consultation; FAO Food and Nutrition: Paper 51; Food and Agriculture Organization of the United Nations: Rome, Italy, 1991.