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L-Glutamine

The body's most abundant amino acid — vital in illness and gut repair, but oversold for muscle and immunity in healthy athletes.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsAmino acidsGut healthRecovery

Glutamine is everywhere in the body and becomes “conditionally essential” when demand outstrips supply. That nuance explains why it helps some people and not others.

Key takeaways

  • Glutamine is conditionally essential — the main fuel for gut lining and immune cells.
  • It is genuinely useful in critical illness, trauma and gut-integrity problems.
  • In healthy, well-fed athletes, it has little effect on muscle growth or immunity.
  • A typical supplemental dose is ~5 g; it's safe.

What it is

Glutamine is the most abundant free amino acid in blood and muscle and a preferred fuel for rapidly dividing cells like those of the gut and immune system. Normally the body makes plenty.

The evidence

Supplementation shows real benefit when demand is very high — critical illness, burns, and some gut conditions. In healthy people with adequate protein, evidence for muscle, recovery or immunity is weak.

Dose & how to use

Common doses are 5–10 g/day. Higher, weight-based dosing is used in clinical settings under supervision.

Safety & who benefits

Safe for healthy adults. Most relevant in clinical/recovery contexts and possibly gut health; unnecessary as a routine muscle supplement.

Bottom line: important where the body is stressed — useful for gut and illness, largely redundant for healthy athletes.

References

Adult research summary for education, not a prescription. These are food supplements, not treatments for disease.

  1. McRae MP. Therapeutic benefits of glutamine: An umbrella review of meta-analyses. Biomed Rep 2017. pmc.ncbi.nlm.nih.gov

This article summarises nutrition and exercise science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.