Glutamine

With glutamine, the science of how it works is far more impressive than the trials in healthy people. These are the questions our naturopaths ask in store to help you tell the two apart.

A good fit if

• Your gut lining is the reason, and you'll take a powder at a dose you can actually reach
• You can give it eight weeks, which is how long the one strong gut trial ran
• You'd rather buy the plain powder than a peptide blend with an unproven absorption story
• Your kidneys are healthy and you take no prescription medicines
• You're comfortable with an honest maybe. The theory is good, but the combined trials across mixed groups of people found no effect

Check with us first if

• You have any kidney concern. In people with diabetic kidney disease, glutamine can cause kidney scarring (glomerulosclerosis) and raised creatinine. It's the clearest safety signal outside hospital.
• You have liver disease or anything that affects how your body handles ammonia. Your body breaks glutamine down into glutamate and ammonia, which both affect your nervous system.
• You plan to take it long term. The safety research says plainly that long-term use by healthy people of all ages hasn't been fully studied.
• You have type 2 diabetes. 30 g a day for six weeks made no difference to blood sugar or insulin after meals, so it isn't a blood sugar strategy either way.
• You take any prescription medicine. No specific interaction with glutamine taken by mouth has been recorded, but no data doesn't mean no interaction.
• You're buying it for training. A review of 47 studies found no benefit, and a protein powder is the better choice for recovery.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.

• L-glutamine free-form powder. Best known for: The standard retail product: plain crystalline amino acid, near-tasteless, dissolved in water. Absorption: No head-to-head absorption study exists here; every trial in the gut evidence used oral glutamine. Typical use: The form used in the one strong gut trial at 5 g three times daily, and the only format you can realistically reach 15 g a day with.
• L-glutamine capsules and tablets. Best known for: The same substance in a smaller per-unit dose. Absorption: No separate evidence. It's the same molecule. Typical use: Convenience only. Reaching 15 g a day means 15 to 30 capsules depending on strength, which is the practical problem with the format.
• Alanyl-glutamine dipeptide. Best known for: Two amino acids bonded together, more stable in solution, which is why hospital intravenous products use it. Absorption: No oral absorption comparison against free glutamine exists here. Typical use: Permitted for oral medicines only in Australia. Every trial held here used it intravenously or in dialysis fluid, and those results don't transfer to a scoop of oral powder.
• Effervescent glutamine. Best known for: A dissolving-tablet format. Absorption: Not studied comparatively. Typical use: One small tolerability trial gave 12.4 g a day for 60 days to 30 older adults and found no change in any measured parameter and no adverse effects.
• Glutamine in arginine or HMB combination formulas. Best known for: Sold as recovery or wound-repair blends. Absorption: Not applicable. Typical use: Confounded. A 15-study review states glutamine was examined only in combination with arginine, which limits any insight into its isolated effect. Never attribute a blend's result to the glutamine in it.
• Glutamine peptides (protein hydrolysate powders). Best known for: Marketed as better absorbed than free glutamine. Absorption: No evidence held here supports that. Typical use: A hydrolysate is a different ingredient from the permitted glutamine item, and the better-absorbed claim has no source behind it.
• Glutamic acid and glutamate. Best known for: Different substances that get confused with glutamine because of the names. Absorption: Not applicable. Typical use: Glutamic acid is permitted only for topical medicines for dermal application in Australia. It is not an oral glutamine substitute, and monosodium glutamate is a different substance again.

Reference values. There isn't one. Glutamine has no Australian reference value. It isn't one of the nutrients the NHMRC covers, so there's no recommended intake and no percentage of daily needs. Any figure given that way has been made up.

Typical supplemental range. Australian powders are usually taken at about 5 g a scoop, one to three times a day. In the trial for gut trouble after an infection, people took 15 g a day as 5 g three times a day for eight weeks. That's the one dose that both matches what's sold here and has a strong result behind it. Other trials used 12.4 g a day for 60 days in older adults, and 30 g a day for six weeks in type 2 diabetes, which had no effect on blood sugar or insulin. In athletes, short-term doses of 20 to 30 g within a few hours, and 0.1 g per kilo four times a day for two weeks, caused no significant side effects.

Upper level. There's no legal limit, so every limit here is based on the evidence rather than the rules. The general view is that up to 30 g a day can be taken without important side effects. Above 200 mg per kilo of body weight, an analysis of athlete studies found a drop in neutrophils, a type of white blood cell. That isn't a benefit, and it's worth knowing if you dose by the scoop rather than by your weight.

Worth knowing. There's less to say about timing than the marketing suggests. The only routines we've seen tested are three doses spread across the day, and one trial that gave it in half a glass of ice-cold water 5 to 10 minutes before each main meal. Nothing supports taking it on an empty stomach or in a post-workout window, so don't let a label tell you otherwise. What you need depends on your age, diet and health, so talk to one of our naturopaths.

This list is the part of the page we will not shorten. If any of it applies to you, talk to one of our naturopaths or your doctor before starting.

• Critically ill adults with multi-organ failure. Early combined intravenous and enteral glutamine was associated with higher 28-day, in-hospital and 6-month mortality.
• Diabetic nephropathy or impaired kidney function. Glutamine can cause glomerulosclerosis and raised serum creatinine in that setting.
• Liver disease, or any condition affecting ammonia handling. Glutamine is metabolised to glutamate and ammonia, both with neurological effects.
• Anyone planning chronic use. The safety literature states chronic consumption by healthy people of all ages has not been fully studied.
• Pregnancy and breastfeeding. No evidence either way; route to a practitioner and do not reassure.
• Children. Tolerated in supervised clinical trials, but no retail dose for healthy children is established.
• Above 200 mg per kilo of body weight. An athlete meta-analysis found reduced neutrophils at that level.
• Anyone on prescription medicine. No interaction is documented, which is not the same as no interaction existing.
• The TGA advisory cache is empty, so this entry cannot state whether any safety advisory about glutamine exists.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before starting.