Of the three macro-nutrients that make up the human diet, protein arguably has the largest variety of functions. From assisting in cell division and repair to maintaining muscle tissue, protein is a vital pillar of support in the human body. Let’s look at what happens when you consume protein.
Let’s say you’re enjoying a nice steak. After you take a bite and swallow, the meat travels down to your stomach, where digestive acids begin to break it down. The bonds in the protein molecules are broken apart by digestive enzymes, turning the large, complex protein molecules into smaller, simpler chains called polypeptides. Finally, in the small intestine, digestive enzymes break up these chains into their smallest units: amino acids.
Amino acids can be thought of as the building blocks of protein molecules. All proteins are made up of a variety of amino acids, and proteins come in all shapes and sizes.
Human beings require 20 different amino acids in order to create all the protein our bodies need. From these 20 amino acids, our bodies create thousands of different kinds of proteins, all of them serving important roles in our bodies.
Although we can make most of the amino acids that we need, we cannot make all of them. There are nine amino acids, called “essential amino acids”, that our bodies cannot make. We must instead obtain these amino acids from our diets. Some essential amino acids include histidine, tryptophan, and valine. Some amino acids that our bodies are able to produce on their own include alanine, aspartic acid, glutamine, and glycine.
Unlike fat and sugar, our bodies do not have readily available stores of protein. We must consume protein every day, making sure to get all the amino acids we need. Long-term failure to do so may lead to muscle autophagy.
Generally speaking, protein-rich foods fall into one of two categories: those that contain a complete amino acid profile (i.e. all nine essential amino acids), and those that do not. The former are called “complete proteins”, whereas the latter is known as “incomplete proteins”. Examples of complete proteins include animal products such as meat, dairy, fish, and eggs. All plant foods, except for those derived from legumes, are incomplete proteins. Plant-based options for complete high-protein foods include beans, soy products, and nut butters.
Formerly, dietitians recommended paring different high protein plant foods together at a single meal as a way to consume all essential amino acids. It was thought that incomplete protein food items had to be eaten at the same time so that the body could create a complete amino acid profile. The Academy of Nutrition and Dietetics states that simply eating a variety of protein-rich plant foods (complete and incomplete) throughout the day can supply all nine essential amino acids, regardless if you pair proteins or not.
Many athletes choose to supplement their diets with isolated amino acids in the belief that doing so may enhance performance, recovery time, and stamina. So far, research into such claims has provided mixed results. Some studies seem to indicate that amino acid supplementation does improve performance, whereas many other studies find no noticeable increase in any of the variables that were looked at. The Journal of the International Society of Sports Nutrition offers a pretty comprehensive overview of the different types of amino acid supplements and their effects.
Regardless if you choose to supplement, you can still get all the amino acids you need as long as you consume a nutrient dense diet that meets your caloric needs.