As our food system adapts to the demands imposed upon it by climate change, the amount of protein consumed from plant-based sources is likely to increase relative to those from animal-based ones.
While there are many benefits to be gained from plant-based proteins, there are also certain nutritional negatives. For example, plant-based whole foods usually, according to a new study published in The Journal of Nutrition, contain antinutritional factors that lower protein digestibility, such as dietary fibre, trypsin inhibitors, and phytates. Beef, on the other hand, shows ‘rapid and complete digestibility upon ingestion.’
One of the key differences between plant-based and animal-based proteins are their ability to stimulate muscle protein synthesis, which is essential to skeletal muscle health. The study aimed to assess what these differences are, and how consequential they might be.
It should be noted that the study is funded by meat industry consumer organisation The Beef Checkoff and meat producer Vion Food Group.
Amino acids and muscle protein synthesis
To know why a certain food stimulates or does not stimulate significant levels of muscle protein synthesis, we must first understand the link between this muscle protein synthesis and the amino acid content of a food.
“Our muscles are composed of proteins, and these are continuously being broken down (old/damaged/unnecessary proteins) and synthesized. Every two to three months the proteins in our muscles are being renewed. In order to maintain and build up muscle proteins, our body needs proteins from our diets. When we ingest proteins, the proteins are being broken down into their building blocks – amino acids,” Philippe Pinckaers, one of the authors of the study, told FoodNavigator.
“In total, there are 20 amino acids, some of which the body can make itself (called non-essential amino acids), some of which the body cannot make itself (called essential amino acids). In order to build muscle proteins we need a sufficient amount of all amino acids, but since the body cannot make the essential amino acids itself, it is important that we ingest a sufficient amount of it though our diet.”
The difference between plant and beef
The study, which involved 16 test subjects, aged between 65 and 85, for their levels of muscle protein synthesis after either a plant-based meal or a meal containing beef (through which most of the protein came from the beef). Both meals had exactly the same amount of protein.
The results showed that the subjects showed a 127% greater plasma essential amino acid concentration after the meat meal than the plant-based meal. One amino acid, plasma leucine, was 139% higher. “Plant-derived proteins contain less leucine in comparison to animal-derived proteins. Thus when the same amount of protein is ingested, less leucine is ingested from the plant-derived source, and less will be available in the circulation,” Pinckaers told us.
It also depends on how digestible the protein in question is. Even if a food contains the same amount of leucine, if it is more digestible in one than the other, more will be released into the circulation.
Finally, the inclusion of whole foods, rather than protein isolates, was highly consequential. “The difference between protein isolates and protein rich whole foods, is that proteins are embedded in the so called ‘food matrix’. Thus proteins are not ingested in their isolation, but as a complete food product, along with other macronutrients (carbohydrates, fats) and micronutrients which all can affect how protein is digested and amino acids are absorbed in the circulation.
“The big difference between whole food animal and plant based sources is the amount of fibre and so called anti-nutritional factors. Although these components can be beneficial in some ways, they do lower the digestibility of the ingested food, and thereby hinder a quick release of amino acids becoming available in the circulation.”
Muscle protein synthesis was also 47% higher on average for those consuming the meat meal, with 12 out of the 16 participants experiencing a higher level of muscle protein synthesis for the beef meal. In fact, the researchers were unable to detect a significant increase in muscle protein synthesis after the vegan meal.
The lower levels of muscle protein synthesis was also linked to the age of the participants. Older adults are more likely to experience anabolic resistance, which reduces the stimulation of muscle protein synthesis by protein and amino acids.
While in this study beef-based meals were more successful at stimulating muscle protein synthesis than plant-based ones, this is due to a number of specific circumstances in the study. For example, the use of whole foods. There are a number of solutions to the problem of muscle protein synthesis that do not involve eating meat.
“Instead of consuming plant-based whole foods, one could use plant-protein isolates which are more easily digested and absorbed than whole foods. Thus, amino acid availability increases. Although in practice this would then mean to supplement on top of the diet,” Pinckaers told us.
Furthermore, “one could fortify the ingested protein source with their limiting essential amino acids. This is not very practical for consumers, but has been used by manufacturers of meat analogues, ensuring a sufficient amount of all amino acids available in a single serving.”
Pinckaers also suggests eating a wider variety of proteins, or simply consuming a greater amount of plant-based proteins, could go a way to solving the problem. Exercise is also a stimulator of muscle protein synthesis, which is why individuals in this study were told to refrain from exercise before eating the meals.
Finally, Pinckaers points out the importance of age in muscle protein synthesis. “Young individuals are very responsive to protein ingestion. This means that, as for now it does not seem that the source of protein matters, as long as a sufficient amount of protein is ingested. For older individuals however, we know that the anabolic response to protein ingestion is less, which means they need more protein to stimulate muscle protein synthesis.”
Sourced From: The Journal of Nutrition
‘Higher Muscle Protein Synthesis Rates Following Ingestion of an Omnivorous Meal Compared with an Isocaloric and Isonitrogenous Vegan Meal in Healthy, Older Adults’
Published on: 14 November 2023
Authors: P. J. M. Pinckaers, J. Domi, H. L Petrick, A. M. Holwerda, J. Trommelen, F. K. Hendriks, L. H. P. Houben, J. P. B. Goessens, J. M. X. van Kranenburg, J. M. Senden, L. C. P. G. M. de Groot, L. B. Verdijk, T. Snijders, L. J. C. van Loon