Glutamine · Weak evidence
What glutamine is for and what the evidence says
The short answer. Glutamine is the most abundant amino acid in the body and it is used by muscle and gut. The problem with the supplement is something else: the body makes it and the diet provides plenty, so adding more changes nothing measurable in a healthy person. Reviews place it among the supplements with limited or no evidence for performance and body composition. Where it is used is in hospital, with critically ill patients, which is a different situation with different doses.
Reviews find no consistent effect. It is listed because it sells, not because it works. No figure on this page is attributed to a specific product: the effect belongs to the ingredient and every number carries its source next to it.
01 What it does and how much
Each row is a measured effect, with the figure the study gives and the source number. Where the evidence gives no figure, the column says so instead of making up a percentage.
| Effect | How much | Detail |
|---|---|---|
| Sports performance | no demonstrated effect | The ISSN review explicitly lists it among supplements with limited or no evidence of improvement. The usual 5 g is the dose it has been studied at, not a dose shown to work. [1] |
| Body composition | no demonstrated effect | There is no support for the idea that it helps healthy people who train gain muscle or lose fat. [1] |
| Immunity and respiratory infections in athletes | no consistent effect | It is glutamine’s classic promise, and the specific review on dose and efficacy finds no consistent benefit at the doses used in sport. [2] |
| Clinical use in critically ill patients | a different context | In severe burns and critically ill patients it does have a studied role. Carrying that over to the gym is the leap marketing makes: neither the metabolic situation nor the doses are anything alike. [2] |
02 How to take it
- Dose. 5 to 10 g a day is what the studies use, without that meaning it works.
- When. There is no evidence-backed timing, because there is no effect to optimise.
- How long before you notice it. There is no demonstrated effect to wait for.
Details that change the result
- It is safe and cheap. The case against it is not risk: it is that the money goes much further on protein or creatine.
- A diet with enough protein already supplies several grams of glutamine a day without buying anything.
- If someone sells it to you to "close the catabolic window" or "repair the gut" after training, they are selling you an extrapolation from the clinic.
03 When it makes sense and when it does not
Worth it if
- On medical advice in a clinical setting. There the decision is not for a supplement website.
- Beyond that there is no sports case that justifies the cost.
Not worth it if
- To gain muscle, recover better or avoid catching colds from training.
- Before you have total protein, creatine and rest covered, which is where the real return is.
04 Sources
Every figure above comes from here. They are position stands from scientific societies, meta-analyses and peer-reviewed reviews: if a claim cannot hang from one of these lines, it is not on the page. References are cited in their original form.
- Kerksick CM et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15:38. La glutamina aparece entre los suplementos con evidencia limitada o nula. doi:10.1186/s12970-018-0242-y
- Gleeson M. Dosing and efficacy of glutamine supplementation in human exercise and sport training. J Nutr. 2008;138(10):2045S-2049S. doi:10.1093/jn/138.10.2045S
This is not medical advice. It is what some studies say about an ingredient, not a protocol for you. With an illness, medication or pregnancy involved, the decision belongs to a healthcare professional who knows you.
Questions about glutamine
Answered with the data on this page
- Does glutamine help you recover better?
- There is no solid evidence that it improves recovery in healthy people who train. Sports nutrition reviews place it among supplements with limited or no evidence. Recovery is driven by sleep, total daily food and training load.
- Then why is it sold so much?
- For two reasonable facts misapplied: it is the most abundant amino acid in muscle and it has a real use in critically ill hospital patients. Neither means that adding more improves anything in someone healthy and well fed.
- Does glutamine help the gut?
- Gut cells use it as fuel, which is where the idea comes from. It has been studied in patients with severe gut damage; in healthy people on a normal diet there is no evidence supporting it as a digestive supplement. With a real digestive problem, see a doctor.
And now, which to buy
Prices, kept apart from the evidence
This page explains what glutamine does and deliberately names no brand. The comparison is the other half: 116 products from 15 stores from €16.49 per kg, sorted by price and by how verifiable their certification is.
Other guides
What each supplement does, with its sources