What L-glutamine is, and where it comes from.

Quick answer. Yes, L-glutamine is an amino acid. It is one of the 20 amino acids in the genetic code and a building block of protein. The body makes its own from glutamic acid and ammonia, so it is classed as non-essential, and it is found in all protein-containing foods, most of all meat, fish, eggs and dairy. Immufix contains 1g per 25g scoop. No health claim for glutamine is authorised in Great Britain, so we describe it and make no claim for it.

Is L-glutamine an amino acid?

Yes. Glutamine is one of the 20 amino acids in the genetic code, the set the body strings together to build proteins. A 2018 review in the journal Nutrients describes it as "a proteinogenic amino acid, i.e., amino acids that are incorporated into proteins", accounting for "5 to 6% of bound amino acids".

The same review notes that glutamine is "nutritionally classified as a non-essential amino acid". That does not mean unimportant. It means the body can make it, so it does not have to come from food in the way the essential amino acids do.

The Norwegian Scientific Committee for Food Safety (VKM), in its 2016 risk assessment, puts it this way: "Glutamine is a non-essential amino acid in the human body (considered conditionally essential in states of disease and stress)." The World Health Organization's report on protein and amino acid requirements also lists glutamine among the amino acids that are "conditionally indispensable".

What does the L in L-glutamine mean?

Amino acids can exist in two mirror-image forms, called L and D. VKM explains that L-glutamine "is the predominant form of glutamine naturally occurring in the body and used in supplements". On a label, glutamine and L-glutamine mean the same ingredient.

How does L-glutamine work in the body?

Most of the glutamine in your body is made there. It is built by an enzyme called glutamine synthetase from glutamic acid and ammonia, and broken back down by another enzyme, glutaminase. These are textbook facts about the body's own chemistry. They are not effects of taking glutamine as an ingredient.

The figures are large compared with any amount in food or supplements:

• 70 to 80g of glutamine is distributed through the body of a healthy 70kg adult, according to the Nutrients review.
• 40 to 80g a day is the body's own estimated production, from isotope studies cited in the same review.
• About 6.8g a day was the average glutamine intake from food among more than 70,000 women in the US Nurses' Health Study.

As for what glutamine does, VKM summarises its general roles as follows: "In addition to its role in protein synthesis and the handling by the body of ammonia (via urea cycle), L-glutamine participates in other complex metabolic pathways". In plain terms, it is part of the protein the body builds, and it carries nitrogen between tissues. Its two nitrogen-containing groups are what let it play that carrier role.

None of this tells you what an extra gram from a supplement does. That is a separate question, and the answer under GB law is set out below.

Which foods contain glutamine?

VKM states that "L-glutamine is available from all protein-containing foods. High-protein foods contain the most (e.g. meat, fish, eggs and dairy products)."

Exact figures are harder to find than you might expect. Standard lab methods turn glutamine into glutamic acid during testing, so, as a 2009 study in the European Journal of Clinical Nutrition puts it, "the content of glutamine in food proteins is not available in nutrient databases". The UK food composition dataset (CoFID 2021) has no amino acid tables either. The researchers instead calculated glutamine from the known sequences of food proteins. Their figures for six foods:

Source: Lenders et al., European Journal of Clinical Nutrition, 2009, gene sequencing method. Values are per 100g of food as described in the study.

The pattern is simple: more protein, more glutamine. A 100g portion of beef provides about 1.2g, slightly more than the 1g in a scoop of Immufix.

How is L-glutamine made for food use?

Glutamine is a permitted food ingredient. In a 2020 opinion, the European Food Safety Authority (EFSA) noted that "Glutamine is authorised for use in food for nutritional purposes", and that it is also used as a flavouring.

The same EFSA opinion, written for its use in animal feed, describes one commercial route: L-glutamine of at least 98% purity "produced by fermentation" using the bacterium Corynebacterium glutamicum. The finished product is "a white crystalline powder".

Is L-glutamine safe to take?

VKM assessed L-glutamine in food supplements at doses from 3,500mg to 16,500mg a day. For adults it concluded that all of these doses "are considered unlikely to cause adverse health effects", and it reached the same conclusion for adolescents and for children aged 10 to 14. VKM also noted a lack of long-term studies in healthy people.

The 1g in a scoop of Immufix is below the lowest dose VKM assessed. If you have a medical condition or take medication, ask your GP or pharmacist before adding any supplement.

Is there a health claim for L-glutamine?

No. Health claims for foods in Great Britain must be on the GB nutrition and health claims register. Many glutamine claims have been submitted over the years, and every one is listed as "Non-authorised". The usual reason given is that "on the basis of the scientific evidence assessed, this claimed effect for this food has not been substantiated."

That is why our label lists the amount and nothing else, and why this article explains what glutamine is rather than what it might do. Glutamine has no nutrient reference value either, so there is no % NRV beside it. Our guide to what NRV means explains why.

Where Immufix fits.

Immufix is one scoop (25g) in around 200ml of water, once a day. Each scoop includes 1g of L-glutamine, alongside 250mg of L-methionine, another amino acid covered in our guide to what methionine is. We make no claim for either. The claims on the pack belong to the vitamins and minerals. Vitamin C contributes to normal collagen formation for the normal function of skin. Riboflavin, niacin and biotin contribute to the maintenance of normal skin. Every amount is on the science page.

The short version.

• L-glutamine is an amino acid, one of the 20 in the genetic code, and a building block of protein.
• The body makes its own, an estimated 40 to 80g a day, so it is classed as non-essential.
• All protein foods contain it. 100g of beef has about 1.2g; 100g of egg about 0.6g.
• VKM found supplement doses up to 16,500mg a day unlikely to cause adverse effects in adults.
• No health claim for glutamine is authorised in Great Britain. Immufix contains 1g per scoop and claims nothing for it.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you have a medical condition, are pregnant, breastfeeding or taking medication, speak to your GP or pharmacist before taking any food supplement.