A Complete Guide to Amino Acids

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Athletes such as bodybuilders and other strength training athletes pay close attention to their amino acid consumption. Some even take supplements to boost their intake and get the right balance of amino acids, especially branched-chain amino acids (BCAAs).

It's helpful to know the facts about these important peptides and to understand what they can and cannot do in your body in order to balance your nutritional intake and reach your health and fitness goals.

What Are Amino Acids?

Amino acids are organic compounds that form proteins when combined. 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 known as 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:

  • Break down food: When protein is consumed and broken down through the digestive process, amino acids are what's left inside the body.
  • Promote muscle growth: Animo acids are metabolized in the muscles to increase strength and endurance.
  • Repair tissue: If muscle tissue becomes damaged from physical activity, amino acids are produced to stimulate muscle protein synthesis and aid in repair.

Our bodies require 20 different amino acids. Together, these 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 its function in the body. Peptide bonds also have a secondary, tertiary, and quaternary structure. The final quaternary structure is a protein.

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. Ultimately, the tasks of proteins are almost too many to count.

Types of Amino Acids

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 include:

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

Nonessential Amino Acids

The 11 nonessential amino acids are produced by the body. These include:

  • Alanine
  • Asparagine
  • Aspartic acid
  • Cysteine
  • Glutamic acid
  • Glutamine
  • Glycine
  • Proline
  • Serine
  • Tyrosine

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

There is also a situation in which an amino acid or other nutrients 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 sometimes considered 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.

Muscle Building

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 BCAA supplementation provides benefits. The results were consistent with other research studies and found that when exercisers ingest a beverage containing BCAA immediately following resistance exercise, they gain improved muscle function.

However, other research reports question the extent of the benefit, citing the influence of the massive supplement industry on scientific studies. Additionally, there is disagreement among researchers about whether or not BCAAs can provide any benefits at all during periods of caloric restriction.

While BCAA supplementation is widely accepted as an effective method to achieve optimal muscle growth, it is important to remember that simply buying and consuming supplements will not make your muscles gain strength and size. A comprehensive plan for training and nutrition needs to be followed.

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.

Muscle Recovery

Branched-chain amino acids are also widely believed to improve muscle recovery following sports or intense exercise. Delayed onset muscle soreness (DOMS) is a condition that many heavy exercisers experience in the 24–48 hours following a strenuous workout. DOMS 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. Other research has shown that BCAA supplementation can help endurance athletes reduce muscle damage.

In addition, a research review published in 2017 by Nutrition found that BCAA use is better than passive recovery or rest after various forms of exhaustive and damaging exercise.

However, it is important to keep BCAA benefits in perspective. A comprehensive review published in 2017 by Nutrients concluded that while BCAAs are known to provide benefits for muscle development, their ability to alleviate muscle damage brought on by resistance training is effective only under certain conditions. These conditions included high BCAA intake, supplementation lasting 10 or more days, and muscle damage that was described as low-to-moderate.

There is some evidence to suggest that BCAA supplementation may help reduce muscle damage caused by strength or endurance training.

Immune Function and Disease Management

Researchers have investigated the role of branched-chain amino acids on immune function and disease management.

For example, a study published in 2018 by Nutrition and Metabolism considered the role of BCAAs in muscle wasting disorders. Researchers concluded that they may provide a therapeutic benefit in cases of chronic renal failure.

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 published in World Journal of Gastroenterology indicates that branched-chain amino acid 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.

Recommended 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. Believe it or not, 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 include:

  • 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

While it isn't likely that you can manage (and distinguish) your intake of specific amino acids, you can make sure that you consume enough overall protein and choose smart 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 BCAAs is in your daily diet.

When you consume foods with amino acids, not only do you benefit from the other nutrients that the food provides, but 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 we need are called complete proteins. Good sources of complete proteins generally include:

  • Animal products, such as meat, poultry, eggs, seafood, and dairy
  • Chia seeds
  • Soy
  • Quinoa

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 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 BCAA's include:

  • Brown rice
  • Chickpeas
  • Lentils
  • Lima beans
  • Meat products
  • Milk (specifically the whey in milk)
  • Nuts (almonds, Brazil nuts, and cashews)
  • Soy protein

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 to take amino acid supplementation, you may be able to increase the levels of nitrogen in your body. 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.

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.

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 buy or use supplements to get the amino acids that you need. It might be tempting to purchase a BCAA supplement in hopes of gaining more muscular or achieving athletic performance that you desire.

Remember that a comprehensive plan including proper training and recovery and good nutrition is necessary for your body to perform at optimum levels.

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13 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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