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Whether you’re trying to grow muscle or improve your diet, you’ve no doubt heard how important it is to eat enough protein. 

But when we’re talking about your protein requirements, what we are really talking about is amino acids.

In this article, we’ll explore the role that these protein building blocks play in your body, plus discuss how you can make sure you’re getting enough of them through your diet. 

What are amino acids? 

Several raw eggs sit in a bowl in a lovely kitchen.

Scientifically speaking, amino acids are chemicals that are made of an amino group and a carboxylic acid group. In simpler terms, though, amino acids are the individual components that build protein molecules

A single protein molecule is made up of 20 different amino acids that are bonded together. These amino acids are: 

  • Histidine
  • Isoleucine
  • Leucine 
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
  • Arginine
  • Alanine
  • Asparagine
  • Aspartic acid
  • Cysteine
  • Glutamic acid
  • Glutamine
  • Glycine
  • Proline
  • Serine
  • Tyrosine 

Essential vs. nonessential amino acids

Amino acids can be further classified into two different groups: essential and nonessential. 

Your body makes 11 of these amino acids on its own, which means that you usually don’t need to eat them on a daily basis to reap their benefits.

These amino acids are called nonessential and include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.  

However, the remaining nine amino acids are essential, which means that your body doesn’t make them on its own, and you need to get them from your diet.

These nine essential amino acids (EAAs for short) are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. 

What do amino acids do?

A man stands outdoors holding weights.

1. Amino acids act as building blocks for muscles 

One of the most important and well-known roles of amino acids is their ability to build protein, which then goes on to create muscles and other tissues in the body.

In other words, amino acids are crucial for the structure of your physique

Your muscles are constantly going through a process of muscle protein synthesis, in which amino acids form protein molecules, and muscle protein degradation, in which protein molecules break into individual amino acids.

As a result, you need to have all of these amino acids in your system in order to maintain and/or grow your muscle mass. 

When it comes to muscle growth, the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine are especially important, since they are thought to trigger muscle protein synthesis.

Evidence has also found that BCAAs are important for helping with muscle recovery after a workout by minimizing soreness and muscle damage. 

However, adequate amounts of all of the EAAs are important for muscle growth and maintenance, since they are all involved in the process of muscle protein synthesis. 

2. Amino acids enhance brain function 

Besides your muscles, amino acids are essential for a crucial organ: your brain.

Many amino acids, like glutamate, can act as neurotransmitters, which are the chemicals that your brain cells use to communicate with each other. 

3. Amino acids support your immune system

Amino acids also seem to play a part in regulating your immune system.

Studies have found that amino acids play roles like activating your immune system’s cells and producing the antibodies that your body needs to fight off infection and disease.

There’s also evidence that amino acid supplementation can be helpful for improving the health of people who suffer from malnutrition. 

4. Amino acids regulate hormones and enzymes

Finally, amino acids play a number of roles in managing important hormones like ghrelin and leptin, both of which influence your metabolism.

There’s even some evidence that certain amino acids can impact insulin, the hormone that controls your blood sugar.

Because hormones are chemical messengers that your body’s various systems use to communicate with each other, this means that amino acids may have huge impacts on your overall health.  

Where can you get amino acids? 

Amino acids can be found in any food that has protein. Some popular sources of amino acids include: 

  • Animal proteins like meat, poultry, seafood, dairy, and eggs
  • Plant-based proteins like grains, legumes, nuts, and seeds 

You can also increase your amino acid intake through supplementation.

For example, many athletes and gym-goers take protein supplements, which are made from the same animal- and plant-based protein sources that you might get your whole food protein from.  

Additionally, you can also take isolated amino acid supplements that provide specific types of amino acids.

These supplements include amino acids that have been isolated and are therefore not considered whole protein sources. BCAA supplements are the most popular version of this, though there are also other amino isolate supplements out there for targeting specific amino acids. 

Why your protein sources matter 

A knife and fork flank an appetizing piece of meat.

Though you can get amino acids from a wide variety of foods with protein, not all protein sources are equally effective when it comes to amino acids.

There are two key factors to keep in mind when evaluating the quality of your protein sources: their completeness and their bioavailability

  • Complete vs. incomplete proteins: Complete proteins are proteins that contain all of the essential amino acids that your body needs in optimal amounts. Incomplete proteins, on the other hand, have one or more amino acids that are present in smaller amounts than you actually need.
  • Bioavailability: Bioavailability is the amount of protein in a food source that your body can actually use. For example, many plant-based foods have antinutritional factors that negatively impact the digestibility of their proteins.   

There are several ways that researchers gauge protein quality.

For example, the protein digestibility corrected amino acid score (PDCAAS) measures protein quality based on how well your body can break down and absorb protein, as well as the amounts of amino acids that are present. 

As a very general rule, plant-based protein sources tend to be incomplete proteins, since they usually don’t have adequate amounts of all of EAAs.

Many of them are also less bioavailable than animal protein since they have other factors that inhibit your ability to absorb all of the protein available. 

Because these two factors vary so much, it’s important to include a variety of high-quality protein sources in your diet if you want to make sure you’re getting adequate amounts of your essential amino acids

How to make sure you’re getting enough amino acids

Based on body weight, the individual EAA estimated requirements for adults are: 

  • Histidine: 8-12 mg/kg 
  • Isoleucine: 10 mg/kg 
  • Leucine: 14 mg/kg 
  • Lysine: 12 mg/kg 
  • Methionine + cystine: 13 mg/kg 
  • Phenylalanine + tyrosine: 14 mg/kg 
  • Threonine: 7 mg/kg
  • Tryptophan: 3.5 mg/kg 
  • Valine: 10 mg/kg 
  • Total: 84 mg/kg 

However, it can be hard to track your individual amino acid intake, especially since nutrition fact labels usually don’t break it down.

Instead, a much easier way to make sure you’re getting adequate amounts of amino acids is simply to make sure that you’re eating enough total protein.  

High-quality protein sources have adequate amounts of all of the amino acids that your body needs.

By ensuring you’re getting enough total protein, and incorporating a variety of different sources, you should be getting all of the amino acids that your body needs to function (and grow, if that’s one of your goals). In other words, by getting enough high-quality protein, you’re also getting enough amino acids. 

The total protein recommendation for adults is 0.8 g/kg of your body weight. However, if you’re looking to build muscle, you should aim for 1.0-1.6 g/kg (depending on your physical activity levels). 

The caveats: special considerations for vegans and vegetarians

Peas, seeds, and other protein sources sit in bowls on a counter.

Because many plant-based protein sources are considered lower in quality than animal-based protein, it’s important to note that people who only or mostly eat plant-based foods will need to pay special attention to their diets if they want to ensure they’re getting enough amino acids

Individual plant-based proteins will usually have one or more amino acids that are not present in optimal amounts. However, other kinds of plant-based proteins often have different limiting amino acids. So, an easy solution here is to eat complementary protein sources! 

Complementary protein sources are two or more different plant-based proteins that can make up for amino acid deficits when eaten together.

For example, beans are low in methionine while grains are low in lysine and threonine. By eating these protein sources together, you can make up the difference and get all the amino acids you need in adequate amounts! 

As a result, vegans and vegetarians should make sure that they’re consuming a wide variety of plant-based proteins every day. By incorporating a mixture of legumes, nuts, seeds, grains, and vegetables into their diets, they can get both enough total protein and enough amino acids. 

Conclusion

When it comes to maintaining your body composition, not to mention your health as a whole, amino acids are a crucial piece of the puzzle.

By eating a diet filled with high-quality protein sources (and by combining plant-based protein sources when necessary), you’ll be filling up on all the amino acids you need to survive and thrive.

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