What Do Amino Acids Do? Their Role in the Human Body
We’ve all heard of amino acids, and most of us have probably even heard the term “essential amino acids” before. But how many of us have ever stopped to ask ourselves, what do amino acids do?
The term “amino acids” refers to a class of simple organic compounds whose members contain at least one amino group (–NH2) and one carboxyl group (–COOH). The word “amino” is a direct reference to the nitrogen (N) atom contained in the molecule. As such, the presence of nitrogen can be considered the defining characteristic of amino acids.
You may recall learning about the building blocks of protein in your high school biology class. But that’s actually a very accurate description of the role amino acids play in the body. Without them, protein would not be created and we would not be here discussing this topic at all.
But how exactly is this feat of protein synthesis accomplished?
Protein Synthesis (and Breakdown)
Your body uses amino acids in a number of different ways, but amino acids are most closely associated with the process of protein synthesis, whereby our cells generate new proteins.
There are actually more than 300 common amino acids, but only 20 of these are incorporated into body proteins. And of these 20 different amino acids, 9 are considered essential because they are not synthesized in the body and must be obtained through dietary sources.
Proteins are actually made up of long chains of amino acids. And even though 20 amino acids may not seem like very many, the body can actually put these 20 amino acids together in seemingly endless combinations, creating literally thousands of different proteins.
In fact, amino acids are so important that essential amino acids (EAAs) are the only dietary macronutrients (nutrients required in large amounts) that must be consumed for survival.
Let that bit of information just sink in for a moment.
Believe it or not, after infancy, we can survive without any carbohydrates at all for the rest of our lives, and we can last 6 months or more without any fats. But our bodies don’t have the ability to store proteins. And since our cells need proteins to function, without amino acids, we wouldn’t survive for long.
Because the body needs proteins to function, these same proteins will eventually be broken down as they're used by the cells. Amino acids thus play a further role in maintaining the balance between this breakdown and synthesis of new proteins.
Here’s how this process works.
In the process of protein breakdown, amino acids are released. These amino acids can then become precursors for the synthesis of new proteins. However, some of the amino acids released as byproducts of protein breakdown will be irreversibly oxidized (chemically combined with oxygen), making them unavailable for reincorporation into new proteins.
Nonessential amino acids (NEAAs) help produce new proteins so that the rates of protein breakdown and synthesis remain balanced. These particular amino acids are produced by the body, so we don’t need to obtain them through dietary sources.
Most dietary proteins are also composed of at least 50% to 60% NEAAs, so in most circumstances, we consume more than enough NEAAs through the food we eat.
By contrast, EAAs can only be obtained from the diet. So, if our diets are lacking in plenty of healthy whole foods, unless we’re supplementing with a high-quality amino acid program for nutritive support, we probably won’t be getting enough EAAs.
And this will result in a progressive loss of protein because the balance between protein synthesis and protein breakdown will be lost, with the rate of breakdown outpacing the rate of synthesis.
To avoid this imbalance and ensure our bodies have access to a steady supply of EAAs, we need to be sure we're including plenty of protein sources in our diets. Some great sources of EAAs include:
Amino Acids and Muscles
If we're not giving our bodies the fuel they crave, one of the first areas we may notice the imbalance is in our muscles.
In other words, without the amino acids the body needs for muscle tissue growth, maintenance, and repair, muscle mass will be lost and exercise performance—and even basic functioning—will suffer.
Let’s break this down and see why amino acids are so important for muscle health.
Muscle Growth and Repair
As we stated earlier, if the balance between protein synthesis and breakdown is tilted in favor of protein breakdown, the amount of protein in the body will decrease.
For muscles, less protein being synthesized means less muscle growth and more muscle breakdown.
Muscles are also the main reservoir of amino acids in the body. If the daily intake of amino acids can’t keep up with the demands of protein synthesis, your muscles will actually release some of their amino acids for use by other parts of the body.
Over time, this emphasis on protein turnover instead of protein synthesis can have implications for everything from exercise performance to maintenance of activities of daily living.
To correct this imbalance and, indeed, shift the focus heavily toward muscle protein synthesis, the world of bodybuilders and endurance athletes has long been interested in the benefits of branched-chain amino acids, or BCAAs.
The BCAAs—leucine, isoleucine, and valine—are touted by fitness junkies for their ability to preserve muscle stores of glycogen (the primary fuel used by muscles during exercise), minimize protein breakdown during exercise, and reduce post-workout muscle soreness and muscle recovery.
On the face of it, that does sound great.
However, as we’ve learned, muscle protein synthesis involves all 20 amino acids working together—linking together—in specific ways to build the protein our bodies need.
If any single EAA is in short supply, protein synthesis will stop as soon as we’ve exhausted its supply. The amino acid in shortest supply during protein synthesis is therefore known as the limiting amino acid.
Making a complete protein requires sufficient quantities of each of the 20 amino acids. Therefore, there is no single best amino acid or group of amino acids for both muscle growth and muscle repair, as the body needs all of them to produce protein.
However, balanced formulations of essential amino acid supplements that emphasize specific amino acids to target specific areas can be helpful.
Amino Acids for Complete Health and Wellness
With all this focus on protein synthesis, we may have given you the impression that that’s all amino acids do. But that would be far from the truth.
In fact, amino acids are involved in an array of processes that go far beyond their role as building blocks of proteins.
For example, certain amino acids serve as neurotransmitters or precursors for the production of other neurotransmitters, and thus help balance our moods and minds.
Amino acids also play a direct role in the regulation of blood flow and blood pressure and the production of nitric oxide—a potent vasodilator affecting everything from cardiovascular to brain health.
In addition, amino acids support immune function, serve as antioxidants, and promote detoxification of harmful substances in the liver.
As you can see, there are many benefits of amino acids, from building muscle to regulating blood flow to detoxifying the body. So, if somebody ever asks you, what do amino acids do? don't be shy. You now have an answer for them.