L-Glutamine

●○○Limited Evidence

The most abundant amino acid in muscle, but supplementation adds little for healthy athletes with adequate protein intake. Most useful for gut permeability and immune support.

Effective Dose

5–10g / day

per clinical evidence

Evidence Level

Limited

Protein & Amino Acids

Mechanism

Conditionally essential amino acid; gut barrier support, immune substrate

primary action

Best For

Gut health

Immune support, Overtraining recovery

This profile is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications.

What Is L-Glutamine?

Glutamine is the most abundant free amino acid in skeletal muscle and plasma. It becomes conditionally essential under extreme physiological stress (burns, surgery, severe illness, overtraining). In healthy athletes eating adequate protein, plasma glutamine depletion rarely occurs, limiting supplementation benefit.

How It Works: The Science

Glutamine is the primary fuel for rapidly dividing cells — enterocytes (gut lining) and immune cells (lymphocytes, macrophages). It supports gut barrier integrity by fuelling tight junction protein synthesis and may reduce intestinal permeability under physiological stress. In muscle, it is involved in glycogen synthesis and osmotic cell volumisation.

Primary Mechanism

Conditionally essential amino acid; gut barrier support, immune substrate

Evidence-Based Benefits

Supports gut barrier integrity under stress

moderate

Multiple ICU and clinical studies — reduces gut permeability in critically ill patients

Reduces infection rates in elite endurance athletes

limited

Castell et al. (1996) — reduced upper respiratory illness post-marathon

May accelerate glycogen resynthesis post-exercise

limited

Antonio & Street (1999) — modest effect; carbohydrate is far more effective

Dosage Guide

Effective Dose

5–10g / day

5–10g/day, often taken post-workout or before bed. Higher doses (20–40g) are used in clinical settings for gut permeability. For athletes, 5g is the commonly studied supplemental dose.

Safety Profile & Side Effects

Extremely safe. The body produces ~50–80g of glutamine per day endogenously. No adverse effects at supplemental doses.

Who Should (and Shouldn't) Take It

Best for

Gut healthImmune supportOvertraining recovery

Who it's for

Athletes undergoing very high training loads with signs of overtraining or frequent illness. Those with diagnosed gut permeability issues or IBS. Healthy athletes eating 1.6g+/kg protein per day gain minimal benefit.

Frequently Asked Questions

What is the recommended dose of L-Glutamine?

5–10g/day, often taken post-workout or before bed. Higher doses (20–40g) are used in clinical settings for gut permeability. For athletes, 5g is the commonly studied supplemental dose.

Is L-Glutamine safe?

Extremely safe. The body produces ~50–80g of glutamine per day endogenously. No adverse effects at supplemental doses.

How does L-Glutamine work?

Who should take L-Glutamine?

Related Ingredients

BCAAs (Leucine / Isoleucine / Valine)EAAs (Essential Amino Acids)Probiotics (Lactobacillus / Bifidobacterium)

Medical Disclaimer

Ingredient profiles are for informational purposes only and do not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications. Full disclaimer →