Glutamine: What It Does, Indian Food Sources and What the Trials Show

Glutamine is the most abundant free amino acid in the human body and a non-essential one: your muscles make it, so no daily requirement exists for it. Reviews of isotope studies put the body's own production at 40 to 80 g a day, several times what food supplies. ICMR-NIN sets no value for glutamine, and FSSAI permits it in supplements without a set amount. Trials in healthy, well-fed people have not shown that extra glutamine improves immunity, performance or body composition. This entry belongs to the proteins and amino acids section.

What is glutamine, and what does it do?

Glutamine is one of the twenty amino acids from which the body builds its proteins, and one of those it can make for itself. ICMR-NIN's Dietary Guidelines for Indians, 2024, count nine amino acids as essential because the body cannot synthesise them, and glutamine is not among the nine. A 2018 review in the journal Nutrients describes a 70 kg adult as holding 70 to 80 g of glutamine, about 80 per cent of it in skeletal muscle, where it makes up 50 to 60 per cent of the free amino acids.

Its work is that of a carrier and a fuel. Glutamine moves nitrogen between organs and carries ammonia through the blood in a harmless form. Cells lining the intestine burn it for energy, in larger quantity than glucose by the review's account, and immune cells consume it at a rate similar to or greater than glucose.

How much glutamine do you need?

No daily amount has been set, because a healthy body makes far more glutamine than it eats. The Nutrients review estimates production at 40 to 80 g a day. Intake from food is much smaller: in a study of 70,356 American women, using a database built from protein sequences, the mean was 6.84 g a day. This entry found no Indian survey that reports glutamine intake. The requirement you do have to meet is the one for protein as a whole.

ICMR-NIN's 2020 recommendation is 0.83 g of protein per kg of body weight a day, 54 g for a 65 kg man and about 46 g for a 55 kg woman, rising to 1 g per kg for people whose cereal-based diets supply low-quality protein. Its amino acid pattern, printed as Table 8.2 of the 2024 guidelines, gives a figure in mg per gram of protein for each essential amino acid, such as 45 mg for lysine, covered in the entry on lysine, and 59 mg for leucine. Glutamine has no row. The protein calculator works out your own protein figure.

The Indian position: no ICMR-NIN requirement and an FSSAI listing without an amount

Schedule II of FSSAI's health supplement and nutraceutical regulations names L-glutamine, beside L-glutamic acid, among the non-essential amino acids a health supplement may contain. The schedule prints no amount against any amino acid. The general rule in the regulations is that added nutrients shall not exceed the recommended daily allowance specified by ICMR, with Codex standards applying where ICMR has specified none, and ICMR has specified none for glutamine.

Every pack must carry the words HEALTH SUPPLEMENT, the amount of each nutrient, the advisory NOT FOR MEDICINAL USE written prominently, a warning not to exceed the recommended daily usage, a statement that the product is no substitute for a varied diet, and any known side effects or interactions. Labelling and advertising may not claim that the product prevents, treats or cures a human disease. A tub that promises to heal a leaky gut is making the kind of claim this rule forbids.

ICMR-NIN's 2024 guidelines do not discuss glutamine by name. Their advice covers the whole category: protein supplement powders in high amounts are not advisable, most athletes can get the protein they need through food alone, and no single supplement form of a nutrient should be overdone.

Glutamine in Indian foods

Every protein food contains glutamine bound into its protein, so there is no special glutamine food. There is a measuring problem, though. The Indian Food Composition Tables 2017 determine most amino acids after acid hydrolysis, a step that converts glutamine into glutamic acid. The glutamic acid column in IFCT therefore reports the two together, and the table below should be read that way. On this combined measure wheat stands out: whole-wheat atta protein carries 29.61 g per 100 g of protein, against 18.92 g for raw milled rice and 21.50 g for toor dal.

How much of that column is glutamine itself? A 2009 study in the European Journal of Clinical Nutrition worked it out from protein sequences instead of hydrolysis. Glutamine was 4.4 per cent of egg protein, 4.8 per cent of beef protein, 8.1 per cent of milk protein, 9.1 per cent of tofu protein, 11.1 per cent of white rice protein and 16.2 per cent of maize protein. Across all the foods it ranged from 1 to 33 per cent, with wholegrain bread at the top. NNWA's table of protein in Indian foods ranks foods by protein, and the atta page gives wheat's full panel.

Does glutamine help the gut?

The biology is real, but the trial evidence in people is thin. Intestinal cells burn glutamine as fuel, and the Nutrients review notes that free glutamine taken by mouth is mainly metabolised in the gut and adds little to blood levels or tissue stores. A 2024 meta-analysis in the journal Amino Acids pooled 10 randomised, placebo-controlled trials with 352 participants and found that glutamine did not significantly change intestinal permeability overall.

A subgroup given very large amounts for under two weeks did show a reduction. One trial, published in Gut in 2019, reported striking results in adults whose irritable bowel syndrome began after an infection: 43 of 54 people on glutamine met the main target, against 3 of 52 on placebo. Its authors asked for large trials to confirm the finding. These were patients under medical care, not healthy adults with occasional bloating. NNWA's guide to gut health basics covers what ordinary food can do.

Does glutamine improve immunity or performance in people who train?

On the published trials, no. The idea grew from an observation: blood glutamine falls after prolonged hard exercise. A review in the Journal of Nutrition found that supplements can hold blood glutamine steady during and after such exercise, yet they do not prevent the changes in immune function that follow it. The level, the review adds, does not fall low enough to slow the multiplication of lymphocytes.

A systematic review in Clinical Nutrition in 2019 gathered 47 studies in athletes and pooled 25 trials. Its conclusion was that glutamine has no effect on athletes' immune systems, aerobic performance or body composition. The one positive signal was a slightly greater reduction in body weight, with no matching change in lean mass or body fat percentage. The Nutrients review agrees: in healthy people on a balanced diet, glutamine supplements do not prevent episodes of illness.

Why is glutamine in critical illness a matter for doctors?

Because the largest trial found harm where benefit was expected. During severe illness, major surgery, trauma and sepsis, the body's demand for glutamine can outrun what it makes, and the amino acid is then described as conditionally essential. A trial in the New England Journal of Medicine in 2013 randomised 1,223 critically ill adults with multiorgan failure, all on ventilators, in 40 intensive care units. Death within 28 days was 32.4 per cent with glutamine against 27.2 per cent without, and deaths in hospital and at six months were significantly higher.

The lesson for a coach or a family member is narrow. Glutamine for a patient in hospital, during cancer treatment or after major surgery is a prescribing decision for the treating team. Nothing in this entry is a guide to it, and a tub bought over the counter should not be added to a patient's diet without that team's agreement.

Can you run short of glutamine?

Not through diet, as far as the evidence shows for a healthy person. No deficiency disease is tied to a low glutamine intake, and the body's own output dwarfs what food supplies. Blood levels do fall in catabolic states: the Nutrients review gives a normal fasting range of 500 to 800 micromoles per litre, dropping to 300 to 400 in such conditions. Those are illnesses, not eating patterns. The risk worth attention in India is a plate short of quality protein, which is a question about dal and milk, not glutamine.

A worked example: a vegetarian lifter's day

This is an illustrative case, not a real person. A 26-year-old vegetarian in Hyderabad weighs 70 kg, lifts weights four evenings a week and is looking at a tub of glutamine with a 5 g scoop. His usual day holds rotis from 150 g of atta, 100 g of rice, 60 g of toor dal, 500 g of milk, some of it set as curd and counted here as milk, 50 g of paneer and 30 g of groundnuts.

Common mistakes and myths about glutamine

The first mistake is to treat similar words as one. Glutamine and glutamic acid are two different amino acids, listed separately in FSSAI's schedule. The second is to read a glutamic acid figure on a food table or a label as glutamine, when hydrolysis has merged the two. The third is to assume plant protein is poor in glutamine: by the sequence method it makes up 11.1 per cent of white rice protein and 4.8 per cent of beef protein.

Glutamine supplements: safety, side effects and when to see a doctor

For healthy adults the short-term record is reasonable. The Journal of Nutrition review reports no ill effect from single intakes of about 20 to 30 g, and no harm in one study where athletes took 28 g a day for 14 days. A 2008 risk assessment in Regulatory Toxicology and Pharmacology found no systematic pattern of adverse effects and named 14 g a day of supplemental glutamine as its observed safe level for normal healthy adults. These figures describe what was tolerated in studies. They are not a recommended amount, and this entry gives no dose.

See a doctor, not a supplement shop, for loose stools that last more than a few weeks, blood in the stool, weight loss you did not intend or infections that keep returning. Stop the supplement and seek advice if you feel unwell after starting it. Do not stop or change a prescribed medicine because you have begun taking an amino acid.

Learning about amino acids at NNWA

Amino acids, protein requirements and the evidence behind sports supplements are taught in the Sports Nutrition course and the Diploma in Nutrition at NNWA, a private skill academy in Kolkata whose classes run online in English and Hindi. Both prepare people to coach healthy clients and to send medical cases to a doctor. Neither is a degree or a dietitian qualification.