What is L-Glutamine?
L-Glutamine is the most abundant amino acid found in muscle. It is a conditionally essential amino acid meaning it is produced naturally by the body; however, at certain times L-Glutamine ingestion via dietary intake is necessary to sustain normal L-Glutamine levels as the body cannot naturally make enough to do so.
Why should you consume L-Glutamine?
Muscle L-Glutamine levels are reduced following endurance exercise lasting longer than two hours(1). Reduced L-Glutamine levels attenuate the body’s immune system response. The release of a signalling molecule, interleukin-6, that stimulates the immune response is suppressed(2), and white blood cell differentiation is reduced(1), which decreases the formation of new cells and reduces immunological function. Ingestion of L-Glutamine appears to alleviate the decline in L-Glutamine levels(3), and potentially reduces immune cell damage(4), and therefore attenuates the reduction in the immune system response following endurance exercise. Ingestion of L-Glutamine is shown to reduce the self-reported incidence of illness in endurance athletes(5). Reduced immune system suppression following exercise decreases the risk of illness and infection which would otherwise cause a reduction in exercise performance.
L-Glutamine ingestion during endurance exercise lasting longer than an hour prevents a significant reduction in L-Glutamine levels which in turn decreases ammonia concentration in the blood(6). L-Glutamine ingestion may therefore be able to attenuate any reduction in performance as a result of reduced L-Glutamine levels or increased ammonia concentration(6). However the effects of L-Glutamine ingestion on endurance exercise performance warrant further research.
When should you consume L-Glutamine?
Based on the available evidence L-Glutamine should be consumed after endurance exercise lasting longer than two hours in order to restore muscle L-Glutamine levels that were decreased during exercise.