Amino acids are the essential components required to build a protein. We know protein is imperative for muscle growth however, some amino acids may be more impactful. Let’s dive in.
How Does Muscle Grow?
Your muscles need two things to grow: protein and resistance training. You will create tiny tears in your muscle fibers when you challenge your muscles through resistance exercises, such as bodyweight exercises, using a resistance band, free weights, or weight machines.
These fibers tear during training so they can grow back stronger and thicker. This is where new muscle grows, through a process known as muscle protein synthesis (MSP), and helps to rebuild the damaged muscle fibers.
To do this, your body requires protein to stimulate MPS, treat damaged muscle tissue, and create new muscle fibers. If you don’t get adequate protein when doing this type of training, your body will break down muscle tissue instead [1].
What is Muscle Protein Synthesis
MPS is a pathway in the body that is responsible for creating new muscle tissue. Many things can help stimulate MPS, such as exercise and protein, as mentioned above. To be more specific, essential amino acids are required. These include 9 of the 20 total amino acids (the other 11 your body can synthesize on its own) [2].
These 9 amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. These are known as your essential amino acids because your body cannot make them, you must obtain them from your diet.
You can find these amino acids in foods such as meat, poultry, seafood, eggs, dairy products, soy, beans, legumes, nuts, and seeds.
Amino Acids and Muscle Synthesis: What is the Link?
Amino acids are essential for MPS because they are the building blocks for creating new muscle tissue. When these are readily available, your muscle tissue cells can use them to create new proteins, increasing total muscle mass [3].
This is especially true for the 9 essential amino acids mentioned above. Since your body cannot synthesize these, you must obtain adequate amounts through your diet.
What are the Best Amino Acids for Muscle Growth?
A diet rich in all 9 essential amino acids is the best way to see muscle growth. However, some research suggests certain essential amino acids may be more beneficial for building muscle.
Branched-chain amino acids (BCAAs), isoleucine, leucine, and valine have become popular athletic supplements because of their potential impacts on MPS, particularly leucine.
BCAAs are a type of essential amino acid that has a branched-chain chemical structure. This structure is what makes it unique compared to the other 17 amino acids. Leucine plays an important role in signaling MPS but all 3 BCAAs are believed to help increase MPS at rest and during recovery after resistance exercise [4].
It’s important to note that, although the research on BCAAs and MPS is promising, it does not show any significant benefits over complete proteins for muscle growth. Research still supports the best outcome for muscle growth when adequate protein is consumed throughout the day, versus individual essential amino acids.
What are Essential Amino Acids?
As mentioned earlier, essential amino acids are 9 of the 20 amino acids our body needs for various functions, including muscle growth. There are 9 that are considered essential because our body is unable to make them on its own and requires us to obtain them from our diet.
Complete vs Incomplete Protein
When a food contains all 9 of the essential amino acids, it is considered a complete source of protein. This is true for animal products, such as meat, poultry, seafood, eggs, and dairy products.
However, there are also plant-based proteins that do not always contain all 9 essential amino acids but can still contribute to your overall protein intake, also known as incomplete protein sources.
To make incomplete protein sources complete, you can pair them with other foods, such as other complete proteins or foods that contain the amino acid the other is missing.
For example, many will pair beans and rice together to create a complete protein from 2 incomplete sources.
Beans are low in the essential amino acid methionine but high in lysine while rice is high in methionine but low in lysine. Combining them ensures you get adequate amounts of all 9 essential amino acids required for them to be complete.
However, you don't have to pair your proteins at every meal to ensure they are “complete” to get what you need. As long as you are including a variety of different plant and/or animal sources of protein in your diet you will likely get adequate amounts and not have to be concerned about whether or not they are all made complete.
Do I Need an Amino Acid Supplement?
While there are many different essential amino acid (EAA) and branched-chain amino acid (BCAA) supplements on the market, Most people do not need to take an amino acid supplement.
If you are getting enough protein in your diet, it’s not needed. However, some feel that additional BCAAs concentrated in their diet through a supplement may further boost muscle growth and recovery. The research on this is lacking but it’s not harmful.
EAAS vs BCAAs: Which is Better?
For the general population, obtaining adequate protein through dietary sources is not difficult. If you have higher protein needs that are hard to meet when trying to build muscle, a protein supplement that contains all 9 essential amino acids may help more than just a BCAA supplement.
TL;DR
Newer research supports the potential benefits of BCAAs for muscle growth as they are believed to help stimulate MPS. However, the research is limited, and stronger evidence supports adequate intake of all 9 essential amino acids to promote new muscle tissue over just emphasizing BCAAs.
With that said, BCAA supplements are not harmful as they are just amino acids but the jury is still out on whether they will provide substantial impacts on muscle growth and recovery over a complete protein.