L-glutamine

What it is

Glutamine is a conditionally essential amino acid that your body makes and that is found in meat, dairy, eggs and beans. It is used heavily by gut lining cells and immune cells.

Supplements are taken for recovery after hard training, gut health and immune support. In hospital it has specific clinical uses under supervision.

Healthy people eating enough protein usually get plenty.

How it works

Glutamine is a fuel for fast-dividing cells, including those in the intestine and immune system. Stress, illness and very heavy training can lower blood levels, which is the logic behind supplementing, though lower levels do not automatically mean supplements help.

What the evidence says

• Weak Muscle recovery and performance in healthy people
  Most well-controlled trials find little or no benefit over adequate protein.
• Limited Gut barrier support (e.g. in IBS-type symptoms)
  Some small trials suggest benefit in particular groups; larger trials are needed.
• Weak Reducing infection after prolonged hard exercise
  Early findings have not held up consistently.
• Moderate Clinical nutrition in burns, critical illness and some cancer treatment
  Used under medical supervision; evidence varies and is not relevant to casual supplementing.

Evidence ratings are our plain-English summary of how much good human research exists, not a promise of results. How we rate evidence.

Dosage and timing

• Common over-the-counter range: 5 to 10 g daily, in one or two servings.
• Higher doses are studied but offer no clear extra benefit.
• Dissolve in cool or warm water; heat can degrade it.
• Check current guidance for long-term use at higher doses.

Forms and what to look for

• L-glutamine powder: cheapest, usually tasteless.
• Capsules: convenient but require many to reach 5 g.
• Glutamine peptides (e.g. in hydrolysed protein) are marketed as better absorbed, evidence is limited.
• Avoid products that list glutamine in a blend without a dose.

What to expect, and when

• You are unlikely to feel any difference.
• Any gut-related effect would take a few weeks of daily use to judge.

Side effects

• Usually well tolerated.
• Bloating, nausea or stomach discomfort at higher doses.
• Dizziness or headache in some.
• Rare reports of rash or itching.

Interactions

• Anticonvulsant medicines: glutamine may affect glutamate balance; ask a pharmacist.
• Chemotherapy: do not take without oncologist approval.
• Lactulose and some liver medicines: speak with a clinician.

Who should avoid it

• People with liver disease or a history of hepatic encephalopathy.
• Anyone with kidney disease.
• People with seizure disorders without medical advice.
• Anyone with a history of mania or bipolar disorder: speak to a clinician.
• Pregnant or breastfeeding people.

Risks and safety

• High doses may raise ammonia levels, which matters for people with liver problems.
• Not banned by WADA, but contamination is a general risk for supplements.
• Marketing often overstates benefits for gut healing.

Buying well: quality and testing

• Single-ingredient powder with stated grams per scoop.
• Informed Sport or NSF for athletes.
• Avoid claims to cure leaky gut or immune disease.
• Check the scoop size; some are tiny.

Bottom line

For most healthy people eating enough protein, glutamine adds little. It may suit those with specific gut complaints under a clinician or dietitian, or people with very high training loads and low protein intake. Spend the money on food first.