Written by Garett Reid | NSCA, CSCS, CISSN, M.S.E.S.S
Fact checked by Sam Coleman, Co-Founder
FACT CHECKED
What are amino acids? Well, we can tell you that they're really important. The problem is that even though they are mentioned often, it's rare to see anyone expound on them. It would be akin to someone telling you how important vitamins are without ever going into the different vitamins, or what each vitamin does. We're going to change that with this article. You'll learn about what the amino acids are, their individual functions, and how much you need. It's a lot to break down, so let's get into it!
What Are Amino Acids?
That's the big question, isn't it?
We'll start by asking another question; what's protein? Everyone knows what protein does, but knowing what it is is a different story. Here's the thing, the term "protein" is just terminology that refers to a long string of amino acids; more than 50. When this string of amino acids is less than 50, it's known as a "peptide."" In other words, protein is made up of amino acids, and amino acids are made up of protein.
But that still doesn't explain what amino acids are.
Amino acids are various organic compounds containing amino and carboxylic acid functional groups. Now, over 500 different amino acids have been identified. For example, creatine is actually an amino acid.
However, of these 500+, 22 stand out. These are the proteinogenic amino acids, which are usually referred to when you hear the term "amino acids" in the fitness and bodybuilding world. This group of amino acids is the only one found in the genetic code of life, as they compose proteins!
The Proteinogenic Amino Acids
So, we've gone over what amino acids are and their general role. Now, let's get a little bit more specific. We mentioned that there are 22 amino acids that make up protein. However, of those 20, only 9 are really concerning, and 6 are a little concerning. Here's the deal.
11 of these amino acids are considered to be either non-essential or conditionally essential.
Non-essential amino acids are able to be synthesized internally through other compounds; this means you don’t need to consume them through your diet.
On the other hand, conditionally essential amino acids are amino acids that are synthesized internally in sufficient amounts under normal circumstances. However, during elevated stress, you may need to consume them through your diet.
These are the 11 non-essential and conditionally essential amino acids. We'll label the conditionally essential amino acid as *
- Arginine*
- Cysteine*
- Glutamine*
- Glycine*
- Proline*
- Tyrosine*
- Alanine
- Aspartic Acid
- Asparagine
- Glutamic acid
- Serine
The Essential Amino Acids
This leaves you with 9 other amino acids collectively known as your essential ones. These amino acids are not synthesized internally, meaning you must consume them in your diet.
These 9 essential amino acids are;
- Leucine
- Isoleucine
- Valine
- Tryptophan
- Phenylalanine
- Threonine
- Methionine
- Lysine
- Histidine
The BCAAs
Now, there's one more subgroup we need to identify first. These are the branch-chain amino acids, better known as your BCAAs. Your BCAAs are a group of three essential amino acids that are structurally unique. In addition, these three amino acids play the biggest role in muscle protein synthesis, making them pivotal in muscle building.
- Leucine
- Isoleucine
- Valine
What Do Amino Acids Do?
So, we have now labeled the amino acids and where they're grouped. There are a lot of amino acids, but we want to briefly explain the function of the essential amino acids and a few of the other amino acids used frequently in fitness, such as glutamine.
Before we get into it, realize that all these amino acids play a role in protein synthesis. Therefore, we’ll only mention this in the amino acids where it plays a crucial role.
With that said, we’ll link a much more intensive breakdown of each amino acid if you so with to visit.
Leucine (BCAA, EAA)
- Protein Synthesis And Muscle Maintenance: Leucine is crucial for muscle protein synthesis and actually stimulates the entire process. It’s regarded as the most important amino acid for building muscle.
- Regulating Blood Sugar: It helps to regulate blood sugar levels by promoting glucose uptake into cells, which can benefit energy metabolism.
- Hormonal Regulation: Leucine stimulates the release of insulin, which is important for nutrient uptake and metabolism.
- Energy Production: Leucine can be used as a source of energy during exercise, especially when glycogen stores are low.
Isoleucine (BCAA, EAA)
- Muscle Metabolism: Like leucine, isoleucine plays a key role in muscle protein synthesis and helps promote muscle recovery after exercise.
- Energy Production: It is involved in energy production, particularly during intense physical activity, by being converted into glucose when needed.
- Immune Function: Isoleucine is important for immune system function, helping the body respond to infections.
- Hemoglobin Production: It contributes to the production of hemoglobin, which is essential for transporting oxygen in the blood.
- Blood Sugar Regulation: Isoleucine can help stabilize blood sugar levels, supporting overall metabolic health.
Valine (BCAA, EAA)
- Muscle Metabolism: Valine plays a crucial role in muscle growth and repair. It helps stimulate protein synthesis, making it vital for athletes and those in strength training.
- Energy Production: Valine can be used as an energy source, especially during exercise, to help maintain endurance.
- Nitrogen Balance: It helps maintain a positive nitrogen balance, crucial for muscle maintenance and growth.
- Cognitive Function: Valine supports brain function by helping regulate neurotransmitters and improving overall mental clarity.
- Immune System Support: Like other branched-chain amino acids (BCAAs), valine can help support immune function and reduce muscle breakdown.
Tryptophan (EAA)
- Serotonin Production: Tryptophan is a precursor to serotonin, a neurotransmitter that helps regulate mood, sleep, and appetite. Adequate levels of tryptophan can contribute to improved mood and reduced symptoms of depression.
- Melatonin Synthesis: It also plays a role in the production of melatonin, the hormone that regulates sleep-wake cycles and helps to promote better sleep quality.
- Niacin Formation: Tryptophan can be converted into niacin (vitamin B3) in the body, which is important for energy metabolism and overall health.
- Immune Function: It may help modulate immune responses and has been linked to overall immune health.
- Stress Response: Tryptophan can influence the body's response to stress and may help improve resilience to stressful situations.
Phenylalanine (EAA)
- Precursor to Neurotransmitters: Phenylalanine is a precursor to important neurotransmitters such as tyrosine, dopamine, norepinephrine, and epinephrine. These neurotransmitters are crucial in mood regulation, cognition, and the body's stress response.
- Mood Regulation: By influencing the production of neurotransmitters, phenylalanine may help support mood and mental well-being.
- Metabolism: It is involved in various metabolic processes and contributes to the production of melanin, the pigment responsible for skin and hair color.
Threonine (EAA)
- Collagen and Elastin Production: Threonine plays a crucial role in the production of collagen and elastin, which are crucial for skin, connective tissues, and overall structural integrity.
- Immune Function: Threonine supports immune system function by aiding in the production of antibodies, which help the body respond to infections.
- Nutrient Absorption: It plays a role in the digestive system, helping to maintain the health of the intestinal lining and improving nutrient absorption.
- Neurotransmitter Regulation: Threonine synthesizes certain neurotransmitters, which can influence mood and cognitive function.
Methionine (EAA)
- Precursor to Other Compounds: Methionine is a precursor to cysteine, another amino acid, and important molecules such as taurine and glutathione.
- Methylation Reactions: Methionine is involved in methylation processes, contributing methyl groups to various biochemical reactions. This is important for DNA methylation, gene regulation, and neurotransmitter synthesis.
- Detoxification: It plays a role in the liver's detoxification processes, helping to eliminate heavy metals and other toxins from the body.
- Metabolism: Methionine is involved in lipid metabolism, helping to prevent fat accumulation in the liver.
- Mood Regulation: Methionine, which is involved in the synthesis of neurotransmitters, may also contribute to mood regulation and cognitive function.
Lysine (EAA)
- Collagen Formation: Lysine is important for the production of collagen, which is essential for the health of skin, cartilage, and connective tissues.
- Immune Function: Lysine supports the immune system by producing antibodies and helping the body fight infections.
- Calcium Absorption: It enhances calcium absorption and may play a role in bone health.
- Hormone and Enzyme Production: Lysine produces various hormones and enzymes, contributing to overall metabolic processes.
- Herpes Simplex Virus: Some studies suggest that lysine may help reduce the frequency and severity of herpes simplex virus outbreaks.
Histidine (EAA)
- Histamine Production: Histidine is a precursor to histamine, a neurotransmitter involved in immune responses, gastric acid secretion, and regulation of physiological functions like sleep-wake cycles.
- pH Regulation: Histidine plays a role in maintaining the body's acid-base balance and can act as a buffer in the blood.
- Metal Ion Binding: It is important for the binding of metal ions, which is essential in many enzymatic processes.
- Cellular Repair and Growth: Histidine is involved in tissue repair and growth, making it significant during recovery from injury or illness.
- Antioxidant Activity: It may help protect cells from oxidative stress by participating in the body's antioxidant defense system.
Glutamine (Conditional)
- Nitrogen Transport: Glutamine is a major carrier of nitrogen in the body, important for various metabolic processes.
- Immune Function: Glutamine supports the immune system by providing energy to immune cells, particularly during stress or illness.
- Gut Health is crucial for maintaining the integrity of the intestinal lining, promoting gut health, and aiding in the prevention of conditions like leaky gut syndrome.
- Energy Source: Cells can use glutamine as an energy source, especially during intense physical activity or stress.
- Acid-Base Balance: It helps regulate the body's acid-base balance by participating in the production of ammonia, which removes excess hydrogen ions.
The Amino Acid Profile Of Protein
Now we know that amino acids have both independent and collective functions as they build up protein. In fact, one of the primary factors determining if a protein is high-quality or not is its amino acid profile.
The amino acid profile is like the "DNA" of a protein source, and it differs between every source. This also plays a major role in the entire plant vs. animal protein debate, which we'll get into right now.
A Complete Protein Vs. Incomplete Protein
One of the biggest points of contention in the fitness industry is the battle between animal protein and plant protein. Which is better? There are many important points here, but probably the biggest is the difference between a complete protein and an incomplete protein.
Above, we spoke about the 9 essential amino acids and how you must consume them. Well, each of those can be considered a nutrient, and your body must consume a certain amount daily to meet its nutritional needs, very much like minerals and vitamins.
With that in mind, let's pretend you only eat one protein source. Now consider;
- Complete protein- Would have the proper ratios of amino acids to meet your nutritional needs.
- Incomplete protein- Is either completely lacking in one of the nine essential amino acids or provides an insufficient amount.
Below, we'll list the minimum percentage of each essential amino acid that a protein must have to meet these needs, assuming you eat a sufficient amount of total protein.
- Leucine 5.5%
- Isoleucine 2.5%
- Valine 3.2%
- Tryptophan 0.7%
- Phenylalanine 4.7%
- Threonine 2.7%
- Methionine 2.5%
- Lysine 5.1%
- Histidine 1.8%
Remember that these are the minimum numbers; many proteins will have much higher percentages for some of these.
With that in mind, while we say "incomplete protein"," there are few true proteins that are completely missing an amino acid. Many are just insufficient in one of the essential amino acids. These will be labeled as the "limiting amino acid"." For example, many legumes, like peas, lack the amino acid methionine.
Now, while a protein may be lacking in these essential amino acids, you could technically eat it as your sole source of protein. However, you would just need to eat more to compensate for that limiting amino acid.
The Limiting Amino Acid And Vegans
We want to discuss the limiting amino acid in more detail. As mentioned, it is the amino acid that is farthest away from your daily requirements. Although amino acids all have their individual functions, they also work together and are required for an array of physiological processes, including muscle protein synthesis.
This means that lacking sufficient quantities of just one amino acid can halt all other processes!
Think about a team race with 20 people. It doesn't matter if 19 members can finish the race in 1 hour; if the 20th member takes 3 hours, the whole team finishes in hours. This is why the concept of plant protein is such a hot topic.
To be clear, we are not saying that vegans can't build muscle. This is especially true today, as plenty of vegan protein powders with optimal amino acids are on the market.
However, a vegan who only eats whole foods is already challenged with getting enough total protein. If they don't eat the proper mixture of protein sources, their processes will be hampered even more!
Here's a crude thought experiment: let's say a vegan ate 150g of protein. However, their limiting amino acid equated to eating just 120g of protein; they would only get the benefits of eating those 120g.
Now, this isn't exactly how it works, as again, there are so many processes going on, but that's a good way to look at it. The best way to get around this as a vegan is to simply eat a diverse range of protein. Perhaps the most common mixture, and studies, is pea and rice protein.
BCAA Percentage Of A Protein
So, we know you need a minimum of all the essential amino acids. Assuming those are met, there's one group of amino acids you want to have a surplus of, the BCAAs.
Numbers can vary depending on the source, but when looking at crude protein, you ideally want a protein source at least 20% BCAA. For example, if you have 100 grams of protein, you would want 20g of leucine, isoleucine, and valine.
To break this down even further, it will usually come in a 2:1:1 ratio of leucine/isoleucine/valine.
For example, here are some typical BCAA percentages and breakdowns of various proteins. Remember this is a crude protein (we'll get into that after).
- Whey Protein Concentrate 23.2% 2: 1.1 : 1.1
- Casein 20.8% 2 : 1.1 : 1.4
- Pea Protein Concentrate 17.3% 2 : 1.1: 1.2
- Soy Protein Concentrate 17.3% 2 : 1.2: 1.2
- Rice Protein Concentrate 18.3% 2: 1.1: 1.6
As we can see, both whey and casein, milk-based proteins, have a larger percentage of BCAAs, with whey having the most. This explains why whey is the most popular source of protein powders.
That said, it's not uncommon to see high-quality protein isolates produce a protein powder with a BCAA percentage of 25% or greater. This could simply be due to the processing methods or a company purposefully adding BCAAs to their powder.
For example, Science Research Whey Protein Isolate delivers 6.9g of BCAA per 25g of protein, which is almost 28% BCAA. This is achieved by specifically adding leucine.
It's important to remember that leucine is the most important amino acid for muscle protein synthesis. To maximize muscle protein synthesis, it's generally recommended that each serving of protein delivers at least 3g of leucine, while more could be better. One of the higher thresholds we've seen is 5g.
For example, let's say you take Optimum Nutrition Gold Whey, one of the most popular protein powders on the market. One serving of 24g protein only delivers 2.64g of leucine. Therefore, you could do a scoop and a quarter or a scoop and a half to increase the leucine.
Amino Acids And Muscle Protein Synthesis
Now, let's look at the specific relationship between amino acids and muscle protein synthesis. Yes, this is why talking about amino acids can be complicated: there are so many processes going on.
That said, the most important process we're concerned with is muscle protein synthesis. Muscle protein synthesis is the process of creating new muscle tissue. While we usually associate it with resistance training or eating protein, it actually occurs at all times, albeit at different rates.
At the same time, another process occurs, which is called muscle protein breakdown. This is the process of muscle being broken down into amino acids, which are transported for certain processes. In other words, these amino acids are constantly combined to make muscle and break down. This is why your total protein intake is so important.
That said, rates of muscle protein synthesis increase during resistance training and the consumption of protein or amino acids. This leads us to the big question…
Should You Take BCAAs Or EAAs?
Due to the role these supplements play in muscle protein synthesis, BCAAs and EAAs are among the biggest supplements on the market. So, which one should you take?
Well, the real question is if you should take any!? This is where supplement companies trick people. Remember that BCAAs and EAAs are protein! In other words, if you're already eating sufficient amounts of protein, taking EAAs and BCAAs isn't really necessary as you're already taking them.
For example, one study that was often used was from 1997. In this study, wrestlers were in a caloric deficit and only eating around 80g of protein at an average weight of 150lbs. This is about half of what bodybuilders are generally advised to take (1g/lb or 2g/kg).
Some wrestlers were then given a large intake of 52 g of BCAAs daily. This resulted in preserving more muscle while losing some fat. While that sounds good for a sales point, it only tells us that BCAAs work well while in a caloric deficit and eating low amounts of protein.
In reality, most people eating sufficient amounts don't need supplementation. If you are training intensely with a lot of volume or frequency it may help.
However, if you did want to try, the general consensus is you should take EAAs due to the need of all the essential amino acids.
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Do Amino Acids Have Calories?
One aspect of supplementation with amino acids is some people will claim they have 0 calories. This makes sense as many nutrition labels have them listed as having 0 amino acids. However, this is not true.
You see, nutrition labels only label our macronutrients as having calories (protein, carbs, fats). If we remember, protein is really just a bunch of amino acids and has 4 calories per gram. Therefore, this means that amino acids have about 4 calories per gram (there is variance between the individual amino acids).
However, because isolated amino acids aren’t counted as protein, they’re usually labeled as having 0 calories.
Amino Acids Are Protein And Protein Is Amino Acids
The main thing to remember when looking at amino acids is that you’re actually looking at the building blocks of protein. They support muscle growth along with a host of other functions making them a crucial part of your fitness lifestyle. Therefore, the next time you hear “amino acids”, you now know they’re talking about the building blocks of your muscle.
Garett Reid
Author