Essential Amino Acids: Definition, Benefits, And Foods

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Medical News TodaySubscribeWhat to know about essential amino acids

Medically reviewed by Natalie Olsen, R.D., L.D., ACSM EP-C — Written by Jennifer Berry on January 21, 2019

Types
Essential amino acids and exercise
How to get essential amino acids
Conditional amino acids
Diet
Takeaway

The body needs 20 different amino acids to maintain good health and normal functioning. People must obtain nine of these amino acids, called the essential amino acids, through food.

Amino acids are compounds that combine to make proteins. When a person eats a food that contains protein, their digestive system breaks the protein down into amino acids. The body then combines the amino acids in various ways to carry out bodily functions.

A healthy body can manufacture the other 11 amino acids, so these do not usually need to enter the body through the diet.

Amino acids build muscles, cause chemical reactions in the body, transport nutrients, prevent illness, and carry out other functions. Amino acid deficiency can result in decreased immunity, digestive problems, depression, fertility issues, lower mental alertness, slowed growth in children, and many other health issues.

Each of the essential amino acids plays a different role in the body, and the symptoms of deficiency vary accordingly.

Types of essential amino acids

tofu-chickpeas-quinoa-and-salad-in-bowl — High protein foods, such as tofu and quinoa, contain amino acids.

There are many types of essential amino acids, including:

Lysine

Lysine plays a vital role in building muscle, maintaining bone strength, aiding recovery from injury or surgery, and regulating hormones, antibodies, and enzymes. It may also have antiviral effects.

There is not a lot of research available on lysine deficiency, but a study on rats indicates that lysine deficiency can lead to stress-induced anxiety.

Histidine

Histidine facilitates growth, the creation of blood cells, and tissue repair. It also helps maintain the special protective covering over nerve cells, which is called the myelin sheath.

The body metabolizes histidine into histamine, which is crucial for immunity, reproductive health, and digestion. The results of a study that recruited women with obesity and metabolic syndrome suggest that histidine supplements may lower BMI and insulin resistance.

Deficiency can cause anemia, and low blood levels appear to be more common among people with arthritis and kidney disease.

Threonine

Threonine is necessary for healthy skin and teeth, as it is a component in tooth enamel, collagen, and elastin. It helps aid fat metabolism and may be beneficial for people with indigestion, anxiety, and mild depression.

A 2018 study found that threonine deficiency in fish led to these animals having a lowered resistance to disease.

Methionine

Methionine and the nonessential amino acid cysteine play a role in the health and flexibility of skin and hair. Methionine also helps keep nails strong. It aids the proper absorption of selenium and zinc and the removal of heavy metals, such as lead and mercury.

Valine

Valine is essential for mental focus, muscle coordination, and emotional calm. People may use valine supplements for muscle growth, tissue repair, and energy.

Deficiency may cause insomnia and reduced mental function.

Isoleucine

Isoleucine helps with wound healing, immunity, blood sugar regulation, and hormone production. It is primarily present in muscle tissue and regulates energy levels.

Older adults may be more prone to isoleucine deficiency than younger people. This deficiency may cause muscle wasting and shaking.

Leucine

Leucine helps regulate blood sugar levels and aids the growth and repair of muscle and bone. It is also necessary for wound healing and the production of growth hormone.

Leucine deficiency can lead to skin rashes, hair loss, and fatigue.

Phenylalanine

drinks-of-ice-tea-or-soda-cola-in-glasses-with-straws — Some diet sodas contain sweeteners with phenylalanine.

Phenylalanine helps the body use other amino acids as well as proteins and enzymes. The body converts phenylalanine to tyrosine, which is necessary for specific brain functions.

Phenylalanine deficiency, though rare, can lead to poor weight gain in infants. It may also cause eczema, fatigue, and memory problems in adults.

Phenylalanine is often in the artificial sweetener aspartame, which manufacturers use to make diet sodas. Large doses of aspartame can increase the levels of phenylalanine in the brain and may cause anxiety and jitteriness and affect sleep.

People with a rare genetic disorder called phenylketonuria (PKU) are unable to metabolize phenylalanine. As a result, they should avoid consuming foods that contain high levels of this amino acid.

Tryptophan

Tryptophan is necessary for proper growth in infants and is a precursor of serotonin and melatonin. Serotonin is a neurotransmitter that regulates appetite, sleep, mood, and pain. Melatonin also regulates sleep.

Tryptophan is a sedative, and it is an ingredient in some sleep aids. One study indicates that tryptophan supplementation can improve mental energy and emotional processing in healthy women.

Tryptophan deficiency can cause a condition called pellagra, which can lead to dementia, skin rashes, and digestive issues.

Essential amino acids and exercise

Many studies show that low levels of protein and essential amino acids affect muscle strength and exercise performance.

According to a 2014 study, not getting enough essential amino acids may cause lower muscle mass in older adults.

An additional study shows that amino acid supplements can help athletes recover after exercise.

How to eat foods with essential amino acids

Doctors previously believed that people had to eat foods that provided all nine essential amino acids in one meal.

As a result, unless an individual was eating meat, eggs, dairy, tofu, or another food with all the essential amino acids, it was necessary to combine two or more plant foods containing all nine, such as rice and beans.

Today, however, that recommendation is different. People who eat vegetarian or vegan diets can get their essential amino acids from various plant foods throughout the day and do not necessarily have to eat them all together at one meal.

Conditional amino acids

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A person should speak to their doctor before taking essential amino acid supplements.

Although 11 of the amino acids are nonessential, humans may require some of them if they are under stress or have an illness. During these times, the body may not be able to make enough of these amino acids to keep up with the increased demand. These amino acids are “conditional,” which means that a person may require them in certain situations.

People may sometimes wish to take essential amino acid supplements. It is best to seek advice from a doctor first regarding safety and dosage.

Incorporating essential amino acids into the diet

Although it is possible to be deficient in essential amino acids, most people can obtain enough of them by eating a diet that includes protein.

The foods in the following list are the most common sources of essential amino acids:

Lysine is in meat, eggs, soy, black beans, quinoa, and pumpkin seeds.
Meat, fish, poultry, nuts, seeds, and whole grains contain large amounts of histidine.
Cottage cheese and wheat germ contain high quantities of threonine.
Methionine is in eggs, grains, nuts, and seeds.
Valine is in soy, cheese, peanuts, mushrooms, whole grains, and vegetables.
Isoleucine is plentiful in meat, fish, poultry, eggs, cheese, lentils, nuts, and seeds.
Dairy, soy, beans, and legumes are sources of leucine.
Phenylalanine is in dairy, meat, poultry, soy, fish, beans, and nuts.
Tryptophan is in most high-protein foods, including wheat germ, cottage cheese, chicken, and turkey.

These are just a few examples of foods that are rich in essential amino acids. All foods that contain protein, whether plant-based or animal-based, will contain at least some of the essential amino acids.

Takeaway

Consuming essential amino acids is crucial for good health.

Eating a variety of foods that contain protein each day is the best way for people to ensure that they are getting adequate amounts of essential amino acids. With today’s modern diet and access to a wide variety of foods, deficiency is rare for people who are generally in good health.

People should always talk to a doctor before using supplements.

Nutrition / Diet

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Compound summary for CID 6106: Leucine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/L-leucine#section=Top
Compound summary for CID 6137: Methionine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/L-methionine#section=Top
Compound summary for CID 6140: Phenylalanine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/L-phenylalanine
Compound summary for CID 6274: Histidine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/L-histidine#section=Top
Compound summary for CID 6287: Valine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/L-valine#section=Top
Compound summary for CID 6288: Threonine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/L-threonine#section=Top
Compound summary for CID 6305: Tryptophan. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/6305
Compound summary for CID 6306: Isoleucine. (n.d.)https://pubchem.ncbi.nlm.nih.gov/compound/l-isoleucine#section=Top
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Thalacker‐Mercer, A. E., & Drummond, M. J. (2014, August 12). The importance of dietary protein for muscle health in inactive, hospitalized older adults. Annals of the New York Academy of Sciences, 1328(1), 1–9.Retrieved fromhttps://nyaspubs.onlinelibrary.wiley.com/doi/full/10.1111/nyas.12509
Vera-Aviles, M., Vantana, E., Kardinasari, E., Koh, N. L., & Latunde-Dada, G. O. (2018, October 21). Protective role of histidine supplementation against oxidative stress damage in the management of anemia of chronic kidney disease. Pharmaceuticals, 11(4), 111https://www.mdpi.com/1424-8247/11/4/111/htm
Waldron, M., Whelan, K., Jeffries, O., Burt, D., Howe, L., & Patterson, S. D. (2017, January 27). The effects of acute branched-chain amino acid supplementation on recovery from a single bout of hypertrophy exercise in resistance-trained athletes [Abstract]. Applied Physiology, Nutrition, and Metabolism, 42(6), 630–636http://www.nrcresearchpress.com/doi/abs/10.1139/apnm-2016-0569?#.XEWxdc_7S88

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Medically reviewed by Natalie Olsen, R.D., L.D., ACSM EP-C — Written by Jennifer Berry on January 21, 2019

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