Amino Acids: Function, Recommended Intake, and More

Medically Reviewed By Sade Meeks, MS, RD
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Amino acids are chemicals known as protein building blocks. They help form proteins, an essential role in the body. We can obtain amino acids through our diets. This article will review what makes up amino acids, their role in the body, and how you can make sure you are getting the correct amounts in your diet.

What are amino acids? 

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Amino acids each function differently, depending on their structure. They form proteins by linking up and bonding together with peptide bonds between them.

Experts may refer to essential and nonessential amino acids.

Some nonessential amino acids are considered conditional.

You need to have all 20 amino acids to maintain your health. However, essential amino acids are not made naturally in the body, unlike nonessential. Therefore, you need to get these other amino acids elsewhere. 

What do amino acids do?

You need all 20 amino acids to keep your body functioning well.

Besides building protein, amino acids produce hormones and neurotransmitters, which help regulate mood, behavior, and sleep. Amino acids also help with:

  • digestion
  • repairing tissue
  • transporting nutrients
  • building muscle
  • strengthening the immune system

Essential amino acids explained

Your body can make nonessential amino acids, but it cannot make essential amino acids. Therefore, you need to get these from an outside source. Essential amino acids can come from the food in your diet or from supplements. 

The nine essential amino acids are:

  • histidine
  • isoleucine
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • threonine
  • tryptophan
  • valine 

Nonessential amino acids explained

Nonessential amino acids and their roles in the body include:

Nonessential amino acidRole in the body
alaninetransferring ammonia to the liver and helping manage blood sugar 
arginineboosting nitrous oxide and helping remove ammonia in the body 
asparaginecarrying ammonia for the body to release and keeping the nervous system functioning
aspartateregulating hormones and producing neurotransmitters
cysteineimportant for protein synthesis, detoxification, and diverse metabolic function
glutamatehelping detoxify the liver and aiding in the inflammatory response
glutaminecarrying nitrogen to tissues and regulating pH balance
glycineacting as a neurotransmitter in the central nervous system and having many roles, such as antioxidant, anti-inflammatory, cryoprotective, and immunomodulatory in peripheral and nervous tissues
prolineaiding in wound healing and boosting the immune system
serinemaking antibodies and helping form the myelin sheath that covers nerve fibers
tyrosineproduced from the essential amino acid phenylalanine, making several hormones including dopamine and thyroid hormone

Conditional amino acids 

Conditional amino acids are considered nonessential amino acids. While your body can make these under normal circumstances, there are certain periods where they are considered essential. An essential amino acid is one that your body cannot make in adequate amounts. 

Infants, and those who are sick, pregnant, or had an injury to the body, might need to take supplements to ensure the right amount of amino acids. 

Conditional amino acids include:

  • Arginine: Doctors recommend this during pregnancy to accommodate a growing fetus.
  • Glutamine: This may be necessary if you are critically ill.
  • Tyrosine: Extra tyrosine may be necessary during periods of high stress.
  • Glycine: This may be useful during pregnancy to accommodate a growing fetus.
  • Serine: Extra serine can be necessary during pregnancy.

Amino acids in food 

One good way to get enough essential amino acids is to eat animal proteins because the body can absorb them efficiently. Complete proteins are foods that contain all nine of the essential amino acids and include:

  • poultry
  • beef
  • eggs
  • dairy products
  • quinoa
  • soy
  • pea protein

Some foods are incomplete proteins, meaning they do not contain all the essential amino acids. If you follow a vegetarian or vegan diet, work with a dietician to make sure you are combining incomplete proteins. This can help ensure that you get all nine amino acids. These foods include:

  • certain grains
  • nuts
  • seeds
  • beans

Learn more dietary sources of protein here.

According to the World Health Organization (WHO), adults have a daily requirement of essential amino acids per 2.2 pounds (lb), or 1 kilogram of body weight, as follows:

  • Histidine: 10 milligrams (mg)
  • Isoleucine: 20 mg
  • Leucine: 39 mg
  • Lysine: 30 mg
  • Methionine: 10.4 mg
  • Phenylalanine: 25 mg
  • Threonine: 15 mg
  • Tryptophan: 4 mg
  • Valine: 26 mg

As long as you eat a balanced diet, you should not need to track your amino acid intake. 

What are the benefits of amino acid supplementation?

There are several reasons why you may want to take amino acid supplements. 

Exercise performance

Branched-chain amino acids (BCAA) may be useful when you want to recover more quickly from working out. Isoleucine, leucine, and valine are BCAAs that many athletes take to help decrease fatigue and improve their performance. 

Improve mood

Since many amino acids aid in neurotransmitter production that regulates mood, giving yourself a boost of amino acids may help regulate your moods.

For instance, tryptophan produces serotonin, and not having enough serotonin can lead to difficulty sleeping or depression. Taking tryptophan might help boost your mood and help you sleep better. 

Recovering from surgery

Ensuring you have adequate amounts of amino acids can help heal wounds. You may need a boost of certain amino acids after an injury or trauma to your body.

If you have had surgery, amino acid supplements can help you recover faster and might prevent complications from an infection. 

Visit our food, nutrition, and diet hub here.

Taking amino acid supplements safely

If you are not getting enough essential amino acids in your diet, consider talking with your healthcare professional about which supplement is best for you. Like many supplements, they are not approved by the Food and Drug Administration (FDA). 

Amino acid supplements can come in powders, capsules, or liquids. If you take amino acids for exercise, you can take them before, during, or after working out to aid muscle recovery. Taking BCAA may work better if you take them after a workout. 

Dosage

Your dosage will depend on what amino acid supplement you are planning on taking and why you are taking it. For example, one 2021 study indicates that 0.14–3 grams of tryptophan per day could help improve mood. Taking 115.6 mg of BCAA per lb can help decrease muscle soreness if taken daily, according to another 2021 study

Talk with your healthcare professional about your individual dosage when it comes to supplements. High levels of amino acids can be harmful to your body. 

Side effects

As with all medications and supplements, there can be side effects when taking amino acid supplements. Side effects will vary depending on the amino acid supplement you are taking. For example, taking BCAAs in high doses can increase your chance of high blood pressure, according to a 2019 study

In general, the FDA considers amino acid supplements to be safe. However, these supplements may interact with your other medications. If you are pregnant or breastfeeding, it is important to talk with your healthcare professional if you want to start a new supplement.  

Summary

There are 20 amino acids present in your body. They are responsible for making proteins and playing other important roles. Your body naturally produces 11 of these amino acids, but you need to get the other nine from outside sources. 

It is not usually necessary to take amino acid supplements since most people can get their essential amino acids by eating protein. 

Discuss with your healthcare professional or dietician if you are concerned you may not be getting enough amino acids from your diet. 

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Medical Reviewer: Sade Meeks, MS, RD
Last Review Date: 2022 May 31
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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