Maastricht University is known for research into improving muscle health and muscle capacity, from athlete to patient. Van Loon: “There are two factors that have a major influence on muscle growth: exercise and nutrition. If we look at nutrition, protein consumption in particular plays a major role. We know that animal protein is of high quality and that consumption of 20-25 grams directly stimulates muscle synthesis. In recent years I have often been asked whether plant-based protein is a good substitute for animal protein when it comes to stimulating muscle growth. We first took inventory of which plant-based proteins there are, how well they are digested and how strongly they could stimulate muscle growth compared to animal proteins. It turned out that potato protein has a fairly balanced amino acid composition. We were able to conduct extensive research into potato protein thanks to funding from the potato industry. Potatoes only contain about 1.5% protein, so to get 20-30 grams of potato protein, you would need to eat 1.3-2 kilograms of potatoes in one meal. In our research we therefore first focused on the type of protein, and not so much on consuming that amount of protein from ‘regular’ food. We therefore used potato protein isolate in our study.”
Prof.dr. Luc van Loon
professor of Physiology of Exercise and Nutrition at Maastricht University
Proteins are broken down into amino acids after consumption. The proteins in our body consist of about 20 different amino acids, eight of which are essential amino acids. Our body cannot produce these essential amino acids. Animal protein sources such as eggs, meat and dairy contain all the amino acids that the human body needs to build body protein. Most plant proteins are deficient in one or more amino acids, generally the amount of methionine, lysine and/or leucine is limited.
Research design
“We first analyzed the isolate of potato protein and milk protein, which matched with what we found in the literature. Thirty grams of the potato protein isolate contains almost the same amount of essential amino acids compared to thirty grams of milk protein. The study group of the randomized, double-blind parallel group study consisted of 24 healthy young men who met our inclusion criteria. With one leg they performed an exercise on a leg extension device, while the other leg remained at rest. After the exercise, half of the participants received a drink containing 30 grams of potato protein, the other half drank 30 grams of milk protein. Blood tests and muscle biopsies were taken at fixed timepoints. The results show that both samples show a rapid increase in several amino acids in the blood, including the amino acid leucine, which we know stimulates protein production.”
Results
In the leg that performed the exercise, the response to the protein was much stronger than in the leg that remained at rest. Van Loon: “Of course we had expected this. The amino acids from the milk protein are available much more quickly than those from the potato protein, but we found no measurable difference in muscle protein synthesis. There was no difference in potato protein versus milk protein in stimulating muscle growth, neither in the first 2 hours nor in the first 5 hours after intake. This outcome is important for companies, as they can say that their potato protein works just as well, or at least not differently, than milk protein. It is of scientific and societal interest to us that it is indeed possible to stimulate muscle synthesis with plant-based proteins. But you should of course realize that this does not automatically mean that this is also possible with ‘regular’ food. In this study we have only looked at the protein itself, without the matrix in which it occurs. For instance, you should also investigate whether factors such as preparation (peeling, boiling, baking), the combination with other foods and the extent to which you chew have an influence. And are there other points that require attention in the case of older people, for example? We are now working on various follow-up studies on protein in daily practice.”
Discussion
“Plant-based proteins generally have a lower quality than animal proteins. It is interesting to see that consuming a lower quality protein does not necessarily mean that you cannot stimulate muscle synthesis,” says Van Loon. “For instance, previous research shows that to stimulate muscle growth you can compensate for a lower quality protein by consuming a larger amount of it. Which leads to the key question: does this mean that the standards for protein intake need to be adjusted? That you need more protein if you get your protein mainly from plant-based sources?”
Want to know more?
Read the original research paper or watch the webinar Plant-based proteins in sports nutrition (in English)
