Amino acids: building blocks of the body

Posted: May 23, 2024
In short
Amino acids are the building blocks of protein. The body uses 20 of them to build its proteins, and nine of these are essential: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine have to come from food (Lopez & Mohiuddin, 2024). Their best-documented benefit concerns muscle: in a meta-analysis of 49 trials with 1,863 adults, extra protein during strength training increased muscle mass and strength, with no further gain in muscle mass above about 1.6 g of protein per kg of body weight a day (Morton et al., 2018). For adults, EFSA recommends 0.83 g of protein per kg of body weight a day (EFSA, 2012).

Updated on: September 30, 2026

⏱ 13 min read

The term amino acid is often used in sports and nutritional science.

  • But what exactly are amino acids and what function do they have in the body?
  • Which amino acids are essential and how can we get them from our food?

Find out more about the function, relevance and food sources of amino acids.

What are amino acids?

Amino acids are small organic compounds that contain both an amino group and an acid group (Hou & Wu, 2018). Far more of them occur in nature than the human body uses to build proteins.

These can be divided into proteinogenic and non-proteinogenic acids. Non-proteinogenic amino acids are found in nature but cannot be used to build body proteins.

 

➤ Did you know that only 20 amino acids are important for the formation of protein in the human body?

 

These 20 amino acids are proteinogenic acids and form the basis of all proteins.

Organic compounds are often referred to as the building blocks of the body, as they play an important role in the human body.

What are the functions of amino acids?

Their tasks include the maintenance of vital processes, such as the synthesis of hormones and neurotransmitters. They therefore also influence numerous metabolic processes in our body and are able to form different tissues such as organs, muscles, skin and hair. They are also the body's main source of nitrogen.

A sufficient supply of amino acids can also:

  • Support weight loss: in 24 trials with 1,063 adults on a calorie-reduced diet, a high-protein diet led to 0.79 kg more weight loss and 0.87 kg more fat loss than a diet with standard protein, while more muscle mass was preserved (Wycherley et al., 2012)
  • Positively influence the build-up and maintenance of muscle mass, especially together with strength training (Morton et al., 2018)
  • Support regeneration after exercise: branched-chain amino acids (BCAAs) reduced muscle soreness compared with a placebo (Fedewa et al., 2019)
  • Help with sleep: tryptophan is the precursor of serotonin and melatonin, and tryptophan supplements shortened the time spent awake after falling asleep, especially at 1 g a day or more (Sutanto et al., 2022)

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What are proteinogenic amino acids?

There are a total of 20 different proteinogenic amino acids, all of which are important for human health. Selenocysteine, which sits at the active centre of enzymes such as glutathione peroxidase, is sometimes counted as a 21st (Lopez & Mohiuddin, 2024).

Proteinogenic means that they form the vital proteins. The number and combination of amino acids determines the quality of a protein source.

All amino acids share the same basic structure, but each has a different side chain. When we eat protein, the body breaks it down into single amino acids and uses them to build its own proteins, enzymes and messengers.

What types of amino acids are there?

Amino acids differ in the form in which they are formed. In other words, whether the body can produce them itself or whether they have to be ingested through food. The acids are basically divided into three types: essential, semi-essential and non-essential amino acids.

What are essential amino acids and what is their function?

There are a total of nine amino acids that can be assigned to this type. They cannot be formed by the body and therefore have to be taken in through food (Lopez & Mohiuddin, 2024).

These amino acids include 

  • Threonine

Threonine is important for healthy skin and connective tissue. It is a component of collagen and elastin and of the mucus proteins that protect the lining of the gut.

  • Lysine

This acid plays an important role in muscle building. It also contributes to maintaining bone strength and supporting recovery after injuries or operations. It helps to regulate hormones, antibodies and enzymes.

  • Valine

Valine is one of the three branched-chain amino acids (BCAAs), together with leucine and isoleucine. Muscles can use it directly as a source of energy. Valine is also often used as a supplement for muscle growth, tissue repair and energy.

  • Leucine

Leucine has a positive effect on the regulation of blood sugar levels. It also supports the growth and repair of muscles and bones, wound healing and the production of growth hormones.

  • Isoleucine

Isoleucine supports wound healing, blood sugar regulation, hormone production and the immune system. This amino acid is mainly found in muscle tissue and, like valine and leucine, belongs to the BCAAs.

  • Phenylalanine

Phenylalanine helps the body to use other amino acids as well as proteins and enzymes. The body converts phenylalanine into tyrosine, which is necessary for certain brain functions. People with the inherited metabolic disorder phenylketonuria (PKU) cannot break down phenylalanine properly and have to limit it in their diet.

  • Tryptophan

Tryptophan is necessary for the proper growth of infants and is a precursor of serotonin and melatonin.

  • Methionine

Methionine is one of the two sulphur-containing amino acids. In its active form, S-adenosylmethionine, it passes on methyl groups to many substances in the body (Lopez & Mohiuddin, 2024). The body also uses it to make cysteine and taurine.

  • Histidine

The body uses histidine to make histamine, a messenger involved in immune reactions and digestion. Sufficient intake is very important, especially during the growth phase, as otherwise growth retardation and functional disorders can occur.

What are non-essential and semi-essential amino acids?

The acids assigned to this group can normally be formed by the body from other amino acids and are therefore non-essential. This means that, unlike the essential amino acids, they do not have to be ingested through food. 

However, if different conditions apply, they may have to be supplied via the food consumed. If this is the case, they are considered semi-essential amino acids. 

Factors that can lead to the body no longer being able to produce the amino acids itself include pregnancy, injuries, growth phases and often babies can also be affected.

These amino acids include:

  • Arginine

Arginine is needed by the body during sport, stress and illness. In addition to enzymes and messenger substances, it also supports the formation of skin, hair and muscles. The body uses it to form nitric oxide, which helps blood vessels to widen.

  • Aspartic acid and asparagine

Aspartic acid helps the body to get rid of nitrogen: it feeds into the urea cycle, in which the liver turns ammonia from protein breakdown into urea that is excreted in the urine. The body makes asparagine from aspartic acid.

  • Tyrosine

Tyrosine is the starting material for neurotransmitters and hormones: the body turns it into adrenaline, noradrenaline, thyroid hormones and the skin pigment melanin (Lopez & Mohiuddin, 2024). As a supplement, tyrosine can improve cognitive performance, especially in short-term stressful or mentally demanding situations (Jongkees et al., 2015).

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  • Cysteine

This amino acid is a major component of keratin which is known as the foundation stone for hair, skin and nails.

  • Glutamine and glutamic acid

These two amino acids are important for a wide range of functions in the body. They serve as a basic substance for the formation of other amino acids such as arginine, glycine, alanine and proline. Glutamine is the most abundant amino acid in the blood and an important fuel for the cells of the gut and the immune system; it is also available as L-glutamine powder. Glutamic acid acts as a messenger in the brain.

  • Glycine

This amino acid is particularly present in structural proteins such as collagen, where it makes up about every third building block. Glycine is also involved in the production of haem, the iron-containing part of haemoglobin, and of building blocks of DNA.

  • Alanine

If there is a lack of energy in the body, alanine is used as an energy source alongside glutamine. It is also responsible for the removal of nitrogen during protein breakdown.

  • Proline

This amino acid, in the form of hydroxyproline, is an important component of collagen. It is therefore important for the structure of bones, skin, tendons and connective tissue.

  • Serine

Serine is a component of compounds that are found in the nerve cell membrane. It therefore plays an important role in our nervous system.

Do amino acids help with muscle growth and recovery?

Muscles are made of protein, so the answer depends mainly on getting enough protein and all the essential amino acids. A meta-analysis of 49 randomised trials with 1,863 adults found that extra protein during at least six weeks of strength training increased strength and fat-free mass. Above a total intake of about 1.6 g of protein per kg of body weight a day, fat-free mass did not increase any further (Morton et al., 2018).

Essential amino acids can also help when muscles are at risk. In one study, older adults stayed in bed for ten days and took either a placebo or 15 g of essential amino acids three times a day; the amino acids showed the potential to preserve muscle function (Ferrando et al., 2010).

Are BCAAs beneficial?

The branched-chain amino acids leucine, isoleucine and valine are popular for recovery after training. In a meta-analysis of eight studies, BCAA supplements clearly reduced muscle soreness after exercise compared with a placebo (Fedewa et al., 2019). To build new muscle protein, however, the body needs all nine essential amino acids, not just the three BCAAs (Wolfe, 2017). BCAAs therefore work best as an addition to a diet that provides enough complete protein.

How much protein do you need?

The European Food Safety Authority (EFSA) recommends 0.83 g of protein per kg of body weight a day for adults (EFSA, 2012). For a person weighing 70 kg, that is about 58 g of protein a day.

Older people need more. An international expert group recommends at least 1.0 to 1.2 g of protein per kg of body weight a day for people over 65, 1.2 g or more for those who are physically active and 1.2 to 1.5 g for most older adults with an acute or chronic illness. Losing muscle and physical function in older age increases the risk of falls and of losing independence (Bauer et al., 2013).

People with severe kidney disease who are not on dialysis may need to limit their protein intake (Bauer et al., 2013). Anyone with kidney disease should therefore talk to their doctor before increasing protein intake or taking amino acid supplements.

Which foods contain amino acids?

There are many foods that contain amino acids. Depending on how "complete " the essential acids are, there are more efficient or less valuable sources.

The following list provides an overview of valuable sources of amino acids:

Fish (tuna, salmon, prawns)

Fish and seafood are particularly protein-rich foods, which is why they should be an integral part of a balanced diet. Fish is also an excellent source of the essential amino acids valine, leucine, threonine, lysine and tryptophan. It is particularly easy to digest and the proteins are very readily available to the body.

Beef and chicken

 

➤ Did you know that beef provides all the amino acids that the body cannot produce itself?

 

This is also the reason why it has an extremely positive effect on muscle protein synthesis. However, depending on which cut of beef is consumed, it should be noted that the calorie content can vary greatly. Chicken meat offers a lower-calorie option and also provides all the essential amino acids. When choosing meat, however, attention should be paid to quality and, if possible, regional products from organic farming should be used.

Soybeans

Soybeans are among the most protein-rich plant foods. The composition of amino acids in this food is very good and it contains all the essential acids. In addition, the beans are easily digested, making it particularly efficient for building up the body's own protein.

Nuts

Walnuts, peanuts and cashews, as well as pistachios, pumpkin seeds and chia seeds, contain a number of important amino acids. This makes nuts and nut butters a very efficient source of protein, fat and fiber. The values and the amino acids contained vary depending on the type of nut. A review of vegetarian and vegan diets concluded that legumes, nuts and seeds are enough to cover the protein needs of adults and that fears of a lack of individual amino acids have been largely overstated (Mariotti & Gardner, 2019).

Spirulina

 

➤ Did you know that spirulina can contain up to 70% protein?

 

This special algae contains all the essential amino acids and is therefore "complete". Spirulina is one of the richest protein sources of microbial origin, with protein levels similar to meat and soybeans (Lupatini et al., 2017).

Nevertheless, it is important to pay attention to the quality of the spirulina supplement, as the values depend heavily on how good the product is and how it has been processed. Spirulina should be taken dried, in capsule form, as tablets or in powder form.

Other good sources of protein are milk, eggs, peas, lentils, quinoa and oatmeal.

Side effects: who should be careful with amino acid supplements?

For supplements, a risk assessment of the available human studies found strong evidence that healthy adults can safely take up to 3 g of taurine, 14 g of L-glutamine and 20 g of L-arginine a day. Higher amounts have also been tested without adverse effects, but the data are not sufficient to be sure about long-term use (Shao & Hathcock, 2008). It is best not to exceed the daily dose stated on the pack.

Some groups should take extra care:

  • Kidney disease: people with severe kidney disease may need to limit protein and should talk to their doctor before taking amino acids (Bauer et al., 2013).
  • Phenylketonuria (PKU): people with this inherited disorder have to avoid phenylalanine and should only take amino acid products that are suitable for them.
  • Pregnancy, breastfeeding and medication: anyone who is pregnant, breastfeeding or taking medication should talk to their doctor before taking single amino acids.

Conclusion

  • Amino acids form the basis of all proteins and are known as the building blocks of the body. They are necessary for the maintenance of vital processes and influence our metabolic processes.
  • It is important to ensure that the nine essential amino acids are taken in with food, as they cannot be produced by the body itself.
  • Foods such as beef, fish and nuts can be consumed.
  • If necessary, the semi-essential acids should also be supplied externally. Babies, growing children, pregnant women and people with injuries in particular may find that the body can no longer produce the amino acids itself.

Frequently asked questions

What foods have all 20 amino acids?

Protein-rich animal foods such as meat, fish, eggs and dairy products provide all 20 amino acids, including all nine essential ones. Among plant foods, soybeans and spirulina also contain all the essential amino acids. A varied plant-based diet with legumes, nuts and seeds covers the protein needs of adults as well.

What are the symptoms of low amino acids?

A lack of individual amino acids is rare and usually results from eating too little protein overall, for example in older age or during illness. Typical consequences are a loss of muscle mass, strength and physical function. Older adults therefore need more protein than younger adults.

What are the side effects of amino acids?

For healthy adults, amino acid supplements are well tolerated at the usual amounts; studies found strong evidence of safety for up to 14 g of L-glutamine and 20 g of L-arginine a day. People with kidney disease or phenylketonuria, pregnant and breastfeeding women and anyone taking medication should talk to their doctor first.

Are BCAAs actually beneficial?

BCAAs can help with recovery: in a meta-analysis, they clearly reduced muscle soreness after exercise compared with a placebo. For building muscle, however, the body needs all nine essential amino acids, so BCAAs work best as an addition to a diet with enough complete protein.

Can amino acids enhance brain function or focus?

Some amino acids are the raw material for messengers in the brain. Tyrosine is the precursor of dopamine and noradrenaline, and a review found that it can improve cognitive performance, especially in short stressful or mentally demanding situations.

 

Sources (in English):

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Lupatini, A. L., Colla, L. M., Canan, C., & Colla, E. (2017). Potential application of microalga Spirulina platensis as a protein source. Journal of the science of food and agriculture, 97(3), 724–732. doi: 10.1002/jsfa.7987

Mariotti, F., & Gardner, C. D. (2019). Dietary Protein and Amino Acids in Vegetarian Diets-A Review. Nutrients, 11(11), 2661. doi: 10.3390/nu11112661

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Fedewa MV, Spencer SO, Williams TD, Becker ZE, Fuqua CA (2019). Effect of branched-Chain Amino Acid Supplementation on Muscle Soreness following Exercise: A Meta-Analysis. International Journal for Vitamin and Nutrition Research, 89(5-6):348-356. doi: 10.1024/0300-9831/a000543

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Important Notice

This guide is for informational purposes only and does not replace professional medical advice.

The content of the Herbano Health Editorial team is carefully researched and based on current scientific studies.

Content created with the support of artificial intelligence and edited by the Herbano Editorial team.