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Exercise & Recovery

What is lysine? A quick guide to this essential amino acid

10/06/20242 min read

Written byMedico Digital

Grilled Toast witch Asparagus, Poached egg, bacon on stone background

Lysine is one of nine essential amino acids, but what does it do? From lysine-rich foods to its possible health benefits, learn the lysine basics here

Summary

1What is lysine?

Lysine is classified as one of the nine ‘essential’ amino acids (the building blocks of proteins needed for muscle growth and repair).

Jump to details below

2The effects of not enough lysine

It could lead to a range of negative effects associated with malnutrition, including symptoms like: loss of appetite, nausea, dizziness and more...

Jump to details below

3The possible health benefits of lysine

As well as its role in muscle growth, other possible health benefits include: May improve bone health, may reduce anxiety, may protect against...

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What is lysine?
How much lysine do we need?
The effects of not enough lysine
Lysine-rich foods
The possible health benefits of lysine
The final say
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Exercise & Recovery

If you’ve not heard of lysine before, you’re definitely not alone.

But, according to emerging research, this essential amino acid can do a lot – from playing a major role in calcium absorption, building muscle protein and recovering from sports injuries to potentially helping with the production of hormones, enzymes and antibodies.¹

What is lysine?

Lysine is classified as one of the nine ‘essential’ amino acids (the building blocks of proteins needed for muscle growth and repair).^2-4,6 It’s described in this way because current literature explains that the human body can’t create it naturally, meaning we must rely on our diets to get enough of it.^2,5

Fortunately, this can be relatively easy to do, as lysine can be found in several different foods, including various protein-rich foods that support your muscle function (but more on these later).^6,7

However, while lysine can be sourced by choosing the right foods, getting too much of it may also lead to stomach difficulties, including abdominal cramps and diarrhoea.⁵ So, it’s important to be aware of how much you should be taking in.

How much lysine do we need?

Some researchers estimate that healthy adults who weigh approximately 70kg need between 800–3,000mg of lysine per day, with daily doses of up to 3g shown to be generally well-tolerated.⁵

On the flip side, consuming very high doses of lysine (more than 10g per day) may cause certain side effects, including nausea and those stomach difficulties mentioned above.⁵

Exactly how you get your recommended daily allowance of lysine is up to you. Many people are fortunate to have a relatively nutritious and well-balanced diet that includes foods that are good sources of lysine. The foods you digest are broken down into amino acids, including lysine, which the body then uses to make new proteins.^7,8

However, you can also take supplements to help boost your lysine levels. In a study, taking a supplement of 25–40 g of lysine monohydrochloride over three to five days was found to show no major side effects.⁹ So, taking them in this form may be particularly useful if you struggle to get enough of it through your diet alone; however consult your doctor before consuming any lysine supplements.

The effects of not enough lysine

So, what can you expect to happen if you don’t have enough lysine in your body?

Since lysine is an essential amino acid, not getting enough of it could lead to a range of negative effects associated with malnutrition, including symptoms like:^2,10,11

loss of appetite
unintentional weight loss
feeling tired all the time
nausea
dizziness
taking a long time to recover after becoming unwell
becoming unwell more often
poor concentration
feeling cold most of the time
low mood, anxiety or depression

However, of all the essential amino acids, lysine appears to be the most well-conserved by the body, so being deficient in it is uncommon.^9,12

Lysine-rich foods

Foods that are high in protein are also rich in lysine, which makes them ideal for making sure that you reach the recommended daily allowance of this important amino acid.⁵

You can either choose animal-based protein or you can get your protein intake from plant-based sources. However, it’s recommended that you get protein from a variety of foods rather than just a single source.¹³

Some of the best sources of protein (and so, by default, lysine) include:^7,13

meats, such as chicken, pork, lamb and beef
eggs
dairy products, such as milk, yoghurt and cheese
fish and shellfish
tofu
nuts and seeds
pulses, like beans, lentils and peas

With plenty of options to choose from, packing your diet full of protein shouldn’t be too challenging. Nevertheless, some people prefer to boost their intake using lysine supplements as well as eating a healthy, balanced diet.

Lysine supplements are usually supplied in tablet form. However, you could also opt for more general amino acid supplements, or boost your protein levels with protein powders, shakes and snacks.

As with any supplement, you should ensure that you take the correct dosage, and always consult your GP before deciding to take lysine supplements in addition to your usual diet.⁵

The possible health benefits of lysine

As well as its role in muscle growth, lysine could also be associated with a range of other possible health benefits.^1,5,9These can include:

May improve bone health

Healthy bones are essential for your day-to-day life, working with your muscles to support your body and movement. Research from an older study indicates that lysine, along with other essential amino acids, may play an important role in keeping your bones healthy.¹⁴

This is because lysine, along with other essential amino acids, is believed to be associated with higher bone mineral density. Despite this, newer studies need to be developed to form a conclusion.^14,15

May reduce anxiety

If you’ve ever experienced anxiety, you’ll know all too well just how crippling it can be.

Well, a small amount of research carried out in poor Syrian communities, indicates that lysine supplementation could play a role in reducing anxiety by blocking receptors that are involved in your body’s stress response.¹⁶Another study in 2007 also shows the possible positive correlation between lysine supplementation and 180 Japanese adults suffering from anxiety and high stress levels. However, research is limited in this area and further research is needed to support this.

May protect against and heal cold sores

Cold sores are more of a nuisance than a serious problem, but getting enough lysine could slow down or prevent their growth.¹⁷

Cold sores are caused by a virus called herpes simplex virus type 1, which triggers fluid-filled blisters to form on the lips and in the corners of the mouth. Some research suggests that taking lysine supplements could reduce the risk of developing cold sores and help them to heal faster However, there isn’t much evidence to support this and further research including longer duration of supplementation and higher dosage levels needs to be investigated^1,9,17

The final say

Lysine is one of several essential amino acids that could help optimise your health and wellbeing.^1,5,9

While you should be able to get enough lysine through the foods you consume, you can also increase your level by taking supplements. Just be careful not to take too much and always remember that these supplements shouldn’t be used as a substitute for a nutritious and balanced diet.

Disclaimer

The advice in this article is for information only and shouldn’t replace medical care. While we strive for accuracy and balance, please be aware that this article may discuss products available for purchase through Holland & Barrett. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements mustn’t be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Sources

Singh, M et al. Medicinal Uses of L-Lysine: Past and Future. International Journal of Research in Pharmaceutical Sciences. 2011;2(4). Available from: https://www.researchgate.net/publication/267817166_Medicinal_Uses_of_L-Lysine_Past_and_Future.
Lopez, MJ. & Mohiuddin, SS. Biochemistry, Essential Amino Acids. [Updated 2024 Apr 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557845/.
NHS Gloucestershire Hospitals Foundation Trust. Amino Acids [Internet]. [cited 2024 Apr 16]. Available from: https://www.gloshospitals.nhs.uk/our-services/services-we-offer/pathology/tests-and-investigations/amino-acids/.
The British Heart Foundation. Heart Matters: How much protein do I need to gain muscle? [Internet]. [cited 2024 Apr 16]. Available from: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/nutrition/ask-the-expert/how-much-protein-should-i-eat-to-gain-muscle.
Thorne Research, Inc. L-Lysine. Alternative Medicine Review. 2007;12(2):169-172. Available from: https://altmedrev.com/wp-content/uploads/2019/02/v12-2-169.pdf.
Aliu E, et al. Amino acid disorders. Ann Transl Med.2018;6(24):471. https://doi.org/10.21037/atm.2018.12.12.
Larson A, Goodman S. Table 5. [Nutritional Requirements for L-lysine, L-Carnitine,...]. [Internet]. Nih.gov. University of Washington, Seattle; 2019 [cited 2024 Jul 4]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546575/table/glutaric-a1.T.nutritional_requirements_f/
British Nutrition Foundation. Protein [Internet]. [cited 2024 Jun 6]. Available from: https://www.nutrition.org.uk/nutritional-information/protein/.
Patel, K. (2022) Lysine. Examine. Available from: https://examine.com/supplements/lysine/research/.
NHS. Symptoms of Malnutrition [Internet]. [cited 2024 Apr 17]. Available from: https://www.nhs.uk/conditions/malnutrition/symptoms/.
Solís-Ortiz S, Arriaga-Avila V, Trejo-Bahena A, Guevara-Guzmán R. Deficiency in the Essential Amino Acids l-Isoleucine, l-Leucine and l-Histidine and Clinical Measures as Predictors of Moderate Depression in Elderly Women: A Discriminant Analysis Study. Nutrients [Internet]. 2021 Oct 29 [cited 2024 Jul 4];13(11):3875–5. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8623361/
Rubey RN. Could lysine supplementation prevent Alzheimer’s dementia? A novel hypothesis. Neuropsychiatric disease and treatment [Internet]. 2010 Oct 1 [cited 2024 Jul 4];707–7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2987503/
Larson A, Goodman S. Glutaric Acidemia Type 1 [Internet]. Nih.gov. University of Washington, Seattle; 2019 [cited 2024 Jul 4]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546575/
Jennings, A., et al. Amino acid intakes are associated with bone mineral density and prevalence of low bone mass in women: Evidence from discordant monozygotic twins. J Bone Miner Res. 2016;31(2):326–35. https://doi.org/10.1002/jbmr.2703.
Protein, lysine and vitamin D: critical role in muscle and bone health. Critical Reviews in Food Science and Nutrition [Internet]. 2022 [cited 2024 Jul 4]; Available from: https://www.tandfonline.com/doi/abs/10.1080/10408398.2020.1855101
Smriga, M., et al. Lysine fortification reduces anxiety and lessens stress in family members in economically weak communities in northwest Syria. Proc Natl Acad Sci USA. 2004;101(22):8285–88. https://doi.org/10.1073/pnas.0402550101.
Mailoo VJ, Rampes S. Lysine for Herpes Simplex Prophylaxis: A Review of the Evidence. Integrative medicine (Encinitas, Calif) [Internet]. 2017 [cited 2024 Jul 4];16(3):42–6. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6419779/