What Are Amino Acids?
Amino acids are organic compounds that combine to form proteins. Proteins provide the basic structural components of our muscles, brain, nervous system, blood, skin, and hair. Protein is also essential for acid-base and fluid balance in the body and helps transport oxygen, fats, and important vitamins and minerals.
Amino acids are the building blocks of protein. Proteins, in turn, are necessary for many of the structures and functions in our bodies.
What Do Amino Acids Do?
Protein is an important macronutrient that we consume in foods like meat and poultry. The human body uses amino acids from protein to perform important body functions, such as:
Breaking down food: When protein is consumed and broken down through the digestive process, amino acids are what's left inside the body.
Promoting muscle growth: Animo acids are metabolized in the muscles to increase strength and endurance.
Repairing tissue: If muscle tissue becomes damaged from physical activity, amino acids are produced to stimulate muscle protein synthesis and aid in repair.
Amino acids make up the enzymes that facilitate the myriad chemical reactions in our bodies. They carry nutrients and other necessary molecules through our blood and across cell membranes and transport signals from one part of the body to another. Furthermore, the antibodies which protect us from illness are proteins.
Types of Amino Acids
Our bodies require 20 different amino acids to perform these tasks. Amino acids are sequenced and folded to combine in almost endless ways. Long chains of amino acids are linked by peptide bonds. The way in which the bonds are linked is called their primary structure and determines function in the body. The final structure is a protein.
Essential Amino Acids
Of the 20 amino acids that we need, our bodies can make 11 of them. The other nine we must get through our diets. These are called essential amino acids because it is essential that we eat them. The nine essential amino acids are:
Nonessential Amino Acids
The 11 nonessential amino acids are produced by the body. These are:
Branched Chain Amino Acids
There are some amino acids called "branched-chain amino acids" or BCAAs. You may have heard athletes and bodybuilders refer to BCAA supplements or foods that provide branched-chain amino acids.
The structure of a BCAA includes a "side chain" or "R group" made up of one carbon and three hydrogen atoms. A branched-chain amino acid includes three essential amino acids: leucine, valine, and isoleucine. These amino acids are metabolized in muscle and are considered to have the greatest impact on muscular development.
Conditional Amino Acids
An amino acid or another nutrient can be "conditionally essential." This means that an amino acid has become essential because the body experiences difficulty making it due to a disorder, illness, or aging.
Cysteine is a conditional amino acid in some populations, including infants, older adults, and people with certain medical conditions.
Health Benefits of Amino Acids
Research studies have investigated the benefits of amino acids, particularly branched-chain amino acids, in the body. Most of these studies focus on BCAA supplementation and whether or not it is necessary for optimal athletic function or performance.
The most widely promoted benefit of branched-chain amino acids is improved muscle development. Many reports, including one study published in 2018 by Frontiers in Physiology, have found that when exercisers ingest a beverage containing BCAA immediately following resistance exercise, they gain improved muscle function.1
However, other research questions the extent of the benefit, citing the influence of the massive supplement industry on scientific studies.2 Additionally, there is disagreement among researchers about whether or not BCAAs can provide any benefits at all during periods of caloric restriction.3
While BCAA supplementation is widely accepted as an effective method to achieve optimal muscle growth, simply buying and consuming supplements will not make your muscles gain strength and size. You must follow a comprehensive plan for training and nutrition.
Including a branched chain amino acid supplement in a comprehensive strength training and nutrition program may help improve stimulation of muscle protein synthesis and boost muscle development.
Branched-chain amino acids are also widely believed to improve muscle recovery following sports or intense exercise. Delayed onset muscle soreness (DOMS) can occur in the 24 to 48 hours following a strenuous workout. It can inhibit performance, especially when it is severe.
Research has demonstrated that BCAA supplementation can be a useful strategy to increase muscle recovery and reduce DOMS following strenuous strength-training activity.4 Other research has shown that BCAA supplementation can help endurance athletes reduce muscle damage,5 and that BCAA use is better than passive recovery or rest after various forms of exhaustive and damaging exercise.6
However, it is important to keep BCAA benefits in perspective. A comprehensive review published in 2017 concluded that while BCAAs provide benefits for muscle development, their ability to alleviate muscle damage is effective only under certain conditions.7 These conditions included high BCAA intake, supplementation lasting 10 or more days, and muscle damage that was described as low-to-moderate.
Immune Function and Disease Management
Researchers have also investigated the role of branched-chain amino acids on the body's response to disease. For example, a study published in 2018 considered the role of BCAAs in muscle wasting disorders. Researchers concluded that BCAAs may provide a therapeutic benefit in cases of chronic renal failure.8
New strategies and further research are needed to understand the role of these amino acids in cases of liver cirrhosis, urea cycle disorders, burn, trauma, sepsis, and cancer.
Improved Liver Function
There is some evidence to suggest that amino acids can improve liver function. A 2013 study showed that BCAA supplementation can help individuals with chronic liver disease manage their symptoms. Patients with advanced liver disease and low concentrations of BCCA who received clinical BCAA supplementation experienced positive results.9
Recommended Amino Acid Intake
According to the National Academy of Medicine guidelines, adults should consume a minimum of 0.8 grams of protein for every kilogram of body weight per day. That means you should consume about seven grams for every 20 pounds of body weight. Most of us consume enough protein.
The amount we need of each of the nine amino acids is different. The recommended daily allowances RDA) for 2.2 pounds (1 kilogram) of body weight are:10
Histidine: 14 mg
Isoleucine: 19 mg
Leucine: 42 mg
Lysine: 38 mg
Methionine (and cysteine): 19 mg
Phenylalanine (and tyrosine): 33 mg
Threonine: 20 mg
Tryptophan: 5 mg
Valine: 24 mg
It isn't necessary to manage your intake of specific amino acids. Just ensure that you consume enough overall protein from healthy protein sources.
Foods High in Amino Acids
While the bulk of research into essential amino acids—specifically branched-chain amino acids—focuses on supplementation, many nutrition experts will tell you that the best way to consume amino acids is in your daily diet.
When you consume foods with amino acids, you benefit from the other nutrients that the food provides. You also have the confidence of knowing exactly what you are consuming.
Foods that contain all of the essential acids in amounts proportional to what the body needs are called complete proteins. Good sources of complete proteins include:
Animal products, such as meat, poultry, eggs, seafood, and dairy
While most complete proteins come from animal products, those who follow a vegetarian diet can rely on certain plant-based proteins to meet their needs. They key is to combine complementary incomplete proteins (such as legumes and whole grains) to create a complete protein.
If you are looking specifically to increase your intake of branched-chain amino acids, there are several plant-based options to choose from. Good sources of plant- and animal-based BCAAs include:
Milk (specifically the whey in milk)
Nuts (almonds, Brazil nuts, and cashews)
Even though most of us consume enough protein, we may not choose sources that provide all of the essential amino acids.
Frequently Asked Questions
What are amino acid supplements good for?
Since health experts recommend fulfilling your amino acid requirement from food sources, amino acid supplements may not be necessary for you unless your doctor recommends them. If you choose amino acid supplementation, you may be able to increase the levels of nitrogen in your body.11 Amino acid supplements may also help maintain adequate levels of amino acid in your muscles.
What makes one amino acid different from another?
The 20 different amino acids, or side chains (R groups), are also divided into two main groups: polar and non-polar. These two main groups describe how the side chains interact with the environment, which affects their function in the body.
Can amino acids be bad for you?
Health experts warn that supplementing with amino acids for nutrition could be dangerous to your health. Pharmacological or clinical supplementation under the supervision of a medical professional should be safe, however.12
A Word From Verywell
Amino acids play an important role in your body, especially when it comes to muscle development. Essential amino acids are especially important because we need to consume them in our diet. Branched-chain amino acids are of particular interest to athletes because of their presumed impact on muscle growth and recovery.
However, it is not necessary to use supplements to get the amino acids that you need. A comprehensive plan including proper training and recovery and good nutrition is necessary for your body to perform at optimum levels.