Also known as: Sustamine, Alanylglutamine, Glutamine dipeptide, AG dipeptide
EnduranceEmerging evidence
Glutamine bonded to alanine, which solves the two problems with plain glutamine: it is stable in solution and absorbed intact. Studied mainly for hydration and endurance rather than muscle.
Typical dose
1.0–2.0 g per day
During prolonged exercise, dissolved in the drink
What it is
L-alanyl-L-glutamine is a dipeptide, two amino acids joined together. That bond changes the practical behaviour of glutamine considerably.
Free glutamine is unstable in water and degrades over hours, and much of an oral dose is consumed by the intestinal cells before it reaches the bloodstream.
The dipeptide is stable in solution, tolerates heat and pH changes, and is absorbed intact through peptide transporters before being split inside the body. That makes it usable in ready-to-drink products where plain glutamine is not.
How it works
Absorption through peptide transporters is faster and more efficient than the amino acid transporters free glutamine relies on, producing a larger rise in blood glutamine from the same amount.
The hydration angle rests on sodium-coupled transport. Amino acid and peptide uptake in the intestine drags sodium and water across with it, enhancing fluid absorption in a similar way to the glucose in an oral rehydration solution.
Glutamine also serves as a primary fuel for intestinal cells and supports gut barrier integrity, which is relevant during prolonged exercise when gut permeability increases.
What the evidence shows
Trials have reported improved fluid absorption and better time to exhaustion when the dipeptide was added to a rehydration drink during prolonged exercise in the heat.
Research has confirmed the superior absorption compared with free glutamine, which is the least contested part of the case.
Trials are small and several come from the same research group. The formulation advantage is real and useful; the performance findings are promising rather than settled.
Dosing
Trials have used around 1 to 2 g added to a fluid volume of roughly 500 to 1,000 ml, taken during exercise rather than before it.
It makes most sense in prolonged sessions, particularly in heat, where fluid absorption is the limiting factor. For a 45-minute gym session there is little for it to do.
Use it in the drink rather than as a capsule, since the hydration mechanism depends on it being in the fluid you are absorbing. It combines sensibly with electrolytes and carbohydrate, which enhance fluid uptake through separate routes.
At a glance
Common forms
Sustamine, Generic L-alanyl-L-glutamine, Within hydration and endurance drinks
Half-life / duration
Absorbed rapidly; acts during the session
Timing
During prolonged exercise, dissolved in the drink
Competition status
Permitted — not on the WADA Prohibited List
Category
Endurance
Safety and side effects
L-alanyl-L-glutamine is well tolerated, with few adverse effects reported. It tends to cause less digestive discomfort than large doses of free glutamine.
Both component amino acids are ordinary dietary constituents present in any protein-containing meal.
Speak to your doctor before use if you take regular medication or are under medical care. Not established at supplemental doses in pregnancy or breastfeeding.
Who should avoid it
Speak to your doctor before use if you take regular medication or are under medical care. Not established at supplemental doses in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
