Amino acids are organic compounds that are needed by the body to make protein, and they are also used in other processes such as neurotransmitter function in the brain and the production of creatine. Nine of these amino acids cannot be made in the body. They are known as essential amino acids because it is essential to have them in your diet (1).

If you are trying to build muscle, work out regularly, or want to prevent progressive muscle loss, you may be looking into taking amino acid supplements on top of your normal diet. What you may not realize is that increasing the amount of amino acids you take in can also help to treat liver disease, reduce your risk of type 2 diabetes, and could even help you get a good night's sleep. We are going to take you through the different types of amino acid supplements, the evidence behind how they work, and some frequently asked questions 

What do amino acids do for you?

Your body needs a constant supply of amino acids to help with muscle repair and growth. It is able to reuse some of the amino acids that are present but some are always lost, so they need to be replaced (1)
Most people can get all of the amino acids they need from their diet, but if you want to increase the level of amino acids you intake, without having to eat a large amount of food, amino acid supplements could be a good route to take.

Increase muscle growth

Since amino acids are needed to help repair and grow muscles, you might be wondering if they can help with your muscle building. Studies have shown that supplementing the diet with amino acids can increase lean muscle mass, increase strength, and improve physical function (2). In this study, a mixture of essential amino acids was used.

Muscle growth can increase by 50% after a significant intake of protein (3). The effect levels off after a certain point, after which more protein doesn't have any effect on muscle growth. It is clear, however, that increasing your amino acid intake can help your muscles to grow. 

Decrease muscle soreness

A common complaint after taking part in exercise is delayed onset muscle soreness (DOMS). DOMS usually starts 24-48 hours after exercising and is a result of microscopic damage to muscle fibers. DOMS isn't just uncomfortable, although it obviously is, it can also decrease performance when working out next. Finding a way to reduce muscle soreness, therefore, is important for anyone who is hoping to increase their fitness or athletic performance.

Taking amino acid supplements can help to reduce DOMS and muscle damage when they are taken on recovery days (4). In this study, a mixture of essential and non-essential amino acids was used, so it is impossible to say if there was one particular amino acid that had the effect. 

Prevent muscle wastage

As we age, our muscle mass decreases. This can be a serious cause for concern both for keeping fitness levels up and because reduced muscle mass can increase the risk of falls and reduce the ability of people to take part in everyday tasks.

When older people were given amino acid supplements, this stimulated protein synthesis and reduced the rate at which muscle mass was lost (5). Supplementation is particularly important for this group because the ability to synthesize amino acids from the protein found in the diet also decreases with age. The muscles retain their ability to grow and repair in response to essential amino acids and BCAAs, however, so taking these directly as a supplement can give benefits to reducing muscle loss that increased protein in the diet cannot. 

Benefits for people with liver disease

The liver is an important part of the protein synthesis process, protein degradation, detoxification, and amino acid metabolism
Several studies have shown that amino acid supplements can help to treat liver diseases such as fatty liver disease, liver injury, hepatic fibrosis, alcohol-induced liver injury, and hepatitis (6). Treating these liver problems at an early stage can help prevent more serious liver diseases such as cirrhosis and liver cancer. When people with cirrhosis of the liver were given amino acid supplements, their model for end-stage liver disease (MELD) scores improved (7).

Antioxidant Supplements and Precursors 

Whole Health's Lysine Ultra

Learn more about lysine ultra

Whole Health's Branched-Chain Amino Acids

Learn more about branched-chain amino acids

Now's Acetyl-L-Carnitine

Learn more about acetyl-L-carnitine

Each of these amino acids can have different effects on the body and its functions, so it is important to have a clear idea about what you are hoping to achieve by taking amino acid supplements before deciding on which one to take. Perhaps the amino acids that have been the focus of most research are branched-chain amino acids.

Lysine Ultra (60 Capsules)
Lysine Ultra (60 Capsules)
Lysine Ultra (60 Capsules) Supplement Facts Label

Lysine Ultra (60 Capsules)

$9.61
NOW® Branched Chain Amino Acids (120 Capsules)
NOW® Branched Chain Amino Acids (120 Capsules)

NOW® Branched Chain Amino Acids

$15.34
NOW® Acetyl-L-Carnitine 500mg (100 Veg Capsules)
NOW® Acetyl-L-Carnitine 500mg (100 Veg Capsules)

NOW® Acetyl-L-Carnitine 500mg (100 Veg Capsules)

$26.99

What are branched-chain amino acids?

Branched-chain in this case refers to the molecular structure of the amino acids. The branched-chain amino acids are leucine, valine, and isoleucine. All of these amino acids are important for making proteins, but they also help to regulate signaling pathways that control protein synthesis (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568273/). Leucine, in particular, is thought to be important because the level of leucine can determine how many of the other amino acids can be utilized. Without enough leucine, therefore, there is no point in increasing the levels of the other amino acids.


Taking branched-chain amino acids alone is thought to stimulate extra protein synthesis by using the stores of other amino acids (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568273/). Although many people argue that it is also important to take enough of the other essential amino acids in order to see a benefit. 

What are the benefits of branched-chain amino acids?

A major benefit of branched-chain amino acids is the role they play in improving liver function, especially for those living with liver disease. They can improve liver function and reduce the risk of complications associated with advanced liver disease (https://www.sciencedirect.com/topics/neuroscience/branched-chain-amino-acid).

They are also the amino acids responsible for reducing perceived exertion and mental fatigue during exercise (https://pubmed.ncbi.nlm.nih.gov/16424144/) and have an impact on reducing muscles loss in older people (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3183816/).

The evidence for BCAAs providing an extra boost to muscle protein synthesis is more mixed, and more research needs to be done to find out if the theory behind why they should do this will play out in practice. Part of the issue is that most of the research to date has been conducted with rats, who have a different muscle composition to humans (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568273/). As well as this, the evidence is that taking BCAAs alone, without an added intake of other essential amino acids, does not help to increase protein synthesis. A full complement of the essential amino acids is likely important for muscle growth and repair.

BCAAs can, however, help to reduce the risk of type 2 diabetes, and can improve insulin function in people who have diabetes. For this reason, BCAAs have been put forward as a treatment for people with pre-diabetes that could help to prevent it from becoming full-blown diabetes (https://www.sciencedirect.com/science/article/pii/B9780128000939000326). 

Branched-chain amino acids and diet

If you would prefer to obtain your branched-chain amino acids from your diet, rather than from supplements, several food sources are rich in branched-chain amino acids:

  • soya protein
  • whey/milk
  • chicken
  • fish
  • eggs
  • chickpeas
  • lentils
  • wholewheat
  • brown rice
  • almonds
  • brazil nuts
  • cashew nuts
  • pumpkin seeds

In Conclusion

Amino acids are a vital compound that helps to support protein synthesis, muscle growth, muscle repair, the synthesis of certain neurotransmitters, and also have an impact on insulin function. Because of this wide array of benefits, making sure that you have enough amino acids is important if you want to remain healthy, retain your muscle mass, or increase your muscle mass. Taking amino acid supplements can help you to ensure that you are getting enough amino acids. Branched-chain amino acids are a particular class that has benefits for improving liver function, preventing fatigue when exercising, retaining muscle mass in older people (when taken alongside other essential amino acids), and in reducing the risk of type 2 diabetes. The evidence that taking them alone to boost muscle growth is mixed and a full complement of essential amino acids is likely important for muscle growth to be at its peak.

F.A.Q- Frequently Asked Questions

Is it safe to take amino acids every day?

There is very little evidence to suggest that taking amino acid supplements every day would be harmful. There is some suggestion that they could increase the risk of osteoporosis long-term, but the evidence to support this idea is mixed (https://www.ncbi.nlm.nih.gov/books/NBK234922/).

Even so, to err on the side of caution, the recommendation is to take no more than double the amount of the recommended dietary allowance (RDA), which is 0.75g/kg for adult males and females (https://www.ncbi.nlm.nih.gov/books/NBK234922/).

Is it OK to take amino acid supplements without working out?

Taking amino acid supplements without working out is unlikely to do you harm, but you also won't see the same benefits in terms of muscle growth that you would if you took them before exercising. Muscles get bigger through tearing and repairing, and it is here that amino acids are able to promote protein synthesis. Your body will excrete any excess amino acids out of the body, so if the amino acids you have taken in your supplement aren't used to help rebuild your muscles, they will just go straight through your body

Can amino acid supplements make you gain weight?

Amino acids are a source of calories, so could contribute to weight gain if they are part of a diet that is above the recommended number of calories. They are not high in calories, however. A gram of amino acid contributes four calories, compared to nine calories from a gram of fat (https://www.livestrong.com/article/430037-can-amino-acids-make-you-gain-weight/).

Amino acids can be used as a source of energy for your body (as a last resort behind carbohydrates and then fats) and excess amino acids can be stored in the body as fat, if they are not used in protein synthesis (https://www.livestrong.com/article/430037-can-amino-acids-make-you-gain-weight/). 

Do amino acids damage the liver?

While amino acids can be useful in treating a variety of liver diseases, excess levels of amino acids (and BCAA in particular) can cause damage to the liver that can result in non-alcoholic fatty liver disease and hepatic injury (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6619856/#:~:text=Increased%20circulating%20BCAA%20has%20been,metabolic%20disorders%20and%20liver%20injury.).

Staying within the recommended dosage for the amino acid supplements you take should be enough to prevent you from having enough of an excess of amino acids to cause liver damage. Your body is quite efficient at excreting amino acids, as long as it isn't overloaded too much. 

Do amino acids affect the kidneys?

For people with chronic kidney disease, a high level of amino acids can cause problems. They can increase the renal plasma flow (RPF), induce hyperfiltration, and increase the acid load, all of which could speed up the progress of kidney disease (https://faseb.onlinelibrary.wiley.com/doi/abs/10.1096/fasebj.31.1_supplement.1030.22). Of all the amino acids, BCAAs show the most dramatic effect on the kidney.

If you do have problems with your kidneys, it would be a good idea to speak to your physician before taking any amino acid supplements. 

Do amino acids help you sleep?

A combination of the amino acids GABA and 5-HTP has been shown to induce sleep in mice who have been subjected to caffeine-induced sleeplessness and because of this have been put forward as a potential treatment for people with insomnia (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5974066/).

Article Sources

  • https://www.ncbi.nlm.nih.gov/books/NBK234922/
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2430042/
  • https://www.scientificamerican.com/article/do-amino-acids-build-bigger-muscles/
  • https://pubmed.ncbi.nlm.nih.gov/17342883/
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3183816/
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6619856/
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478300/
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478300/

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