Glutamine (C5H10N2O3)

Glutamine is the most abundant amino acid in the muscle cells, and in the body in general (about 60 per cent), and is stored in skeletal muscles, but is also found in the blood. Although glutamine is a dispensable amino acid, its supplementation becomes essential with certain conditions, such as some gastrointestinal disorders. Glutamine has many biochemical functions, including protein synthesis and increased glycogen production, and is used at a high rate by cells of the immune system.

Since prolonged or intense training causes glutamine levels to fall sharply, glutamine supplementation is thought to guard athletes from infection by maintaining the immune system, and is also claimed to increase strength, muscle mass and time to exhaustion. However, scientific evidence does not generally support such claims; there has been no strong evidence to suggest that glutamine supplementation improves lean body mass, strength in resistance training, or increased glycogen synthesis.


Interestingly though, a couple of more recent trials (in 2010 and 2012) found that glutamine supplementation significantly improved time to exhaustion in trained endurance athletes, and visual reaction time and skill performance in basketball players. In the endurance trial the athletes who showed positive results ingested very different amounts of glutamine; 0.05g per kg of BM or 0.2g per kg of BM, so for a 75-kg athlete this is 3.75g and 15g of glutamine, respectively.

In the basketball trial, the athletes who ingested either one or two grammes of glutamine in 500ml of water did significantly better than those who ingested water alone. As it stands, the intakes vary considerably, the positive trials are few and they are way outnumbered by those that do not show any confirmed benefits. For these reasons its usage is not advocated in this article and so no dosage is suggested.


Glutamine comes in two forms

D-glutamine and L-glutamine. They are mirror images of each other but it is L-glutamine that is of use to the body. In commercial products, the terms glutamine and L-glutamine are often used interchangeably (as in this text), so whether they are labelled ‘Glutamine’ or ‘L-Glutamine’ makes no difference. However, a closer inspection of the ingredients will often show that the content of L-glutamine is not always 100 per cent, and sometimes it is as low as 60 per cent. The serving suggestions are normally about 5g once or twice a day with fluids.

There are no known side-effects associated with glutamine supplementation

Trials have tested a variety of doses, including 20-30g a day – in one case 28g a day for 14 days, and 0.65g per kg of BM (that is over 50g for an 80-kg athlete). None showed any adverse side-effects, and in blood tests no abnormal levels of glutamine were observed. However, it is not certain whether glutamine supplements are safe if you are pregnant or lactating, so in such cases it is strongly advisable to seek medical advice beforehand.

Animal proteins are the richest source of glutamine – especially beef, chicken, pork, all types of fish, milk and other dairy products – but other good sources include beans, cabbage, spinach and parsley.

You can find more information about sport nutrition here!

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