Amino Acids

Amino Acid Functions, Benefits, and Food Sources

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Some athletes (especially 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.

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 most commonly referred to as the building blocks of protein. Protein is an important macronutrient that we consume in foods like meat and poultry. But proteins inside the body serve several key functions.

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 proteins. Proteins, in turn, are necessary for many of the structures and functions in our bodies.

The Role of Amino Acids in the Body

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!

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 essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential amino acids include alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine. These amino acids are made by the body.

There is also a situation in which an amino acid or other nutrients can be "conditionally essential"—amino acids that become essential because the body has trouble making it due to a disorder, illness, or aging.

For example, cysteine is sometimes considered a conditionally essential amino acid in special populations including infants, the elderly, and people with certain medical conditions.

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.

BCAAs are essential amino acids that have a branched R chain—essentially a side chain. These amino acids are metabolized in the muscle and are considered to have the greatest impact on muscle development.

Branched-chain amino acids include leucine, valine, and isoleucine.

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 Development

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. Their findings 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 to 48 hours following a strenuous workout. DOMS can inhibit performance, especially when it is severe.

Published research has demonstrated that BCAA supplementation can be a useful strategy to increase muscle recovery and reduce DOMS following strenuous strength-training activity. Additional research has shown that BCAA supplementation can help endurance athletes reduce muscle damage.

Lastly, 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.

Research has shown 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. But 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.

Good Food Sources of 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. Several investigational reports have exposed a supplement industry that doesn't always provide products that include ingredients that they claim to include.

Recommended Levels

The amount we need of each of the amino acids is different. For example, according to the standards of the World Health Organization, a person who weighs 154 pounds (70 kg) needs 280mg of tryptophan daily, but 2100 mg of lysine and 2730 mg of leucine.

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.

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.

Amino Acid Food Sources

Even though most of us consume enough protein, we may not choose sources that provide all of the essential amino acids.

Foods that contain all of the essential acids in amounts proportional to what we need are called complete proteins. In general, animal products, such as meat, poultry, eggs, seafood, and dairy are good sources of complete proteins.

Soy, quinoa, and chia seeds are plant-sources of complete proteins. People who eat a vegetarian diet can rely on plant-based complete proteins, but can also be successful at meeting their needs when they combine complementary incomplete proteins.

If you are looking specifically to increase your intake of branched-chain amino acids, good sources include milk (specifically the whey in milk), soy protein, chickpeas, lima beans, meat products, lentils, brown rice, and nuts (almonds, Brazil nuts, and cashews).

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 the muscular body or 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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