Glutamine enhances endurance in new study

Glutamine enhances endurance in new study

Glutamine is a supplement that inspires fervour and hatred in equal measure with its advocates considering Glutamine essential for hard training bodybuilders while its detractors say it is a worthless supplement for many.

A recent study (1) examined the effectiveness of L-Alanyl-L-Glutamine during hydration stress in endurance exercise. This is also known by the brand name Sustamine and is included within a range of bodybuilding supplements. The researchers in this study looked to examine the effects of L-Alanyl-L-Glutamine on performance as well as markers of fluid regulation, oxidative stress and immune and inflammatory health markers.



Ten physically active young males with an average age of 21 and a bodyfat level of 12% volunteered to participate in this study. At an initial testing session (T1) the men provided a blood draw and performed a maximal exercise test while fully hydrated. On four subsequent occasions, the subjects were dehydrated so that their body mass dropped by 2.5%. During their second test (T2), subjects dropped their weight by 2.5% and were kept dehydrated at this level while on tests 3-5, the subjects reached their goals and were then partially rehydrated to 1.5% of their baseline body mass (their drop in body mass was just 1%). During T3 the subjects rehydrated by drinking water while during T4 they consumed 0.05g/kg of a supplement containing LALG and during T5 they consumed 0.20g/kg of the LALG supplement.

Subjects in all tests exercised at 75% of their VO2 max on a cycle ergometer. During T2-T5 blood draws we’re conducted after dehydration (D), immediately before exercise (BE), and also after exercise (AE). Resting 24 hour blood samples were also taken and assessed for a range of markers including glutamine, testosterone, cortisol and a number of markers associated with inflammation and growth as well as salts such as potassium and sodium.


Glutamine concentrations for T5 (the high dosed glutamine group) were significantly higher after rehydration when tested before the exercise bout (BE) and after exercise (AE) compared to trials 2-4. When assessing the impact on performance, the research showed that compared to other tests (T1-3), time to exhaustion was significantly greater for T4 and even more so for T5. In addition, blood levels of sodium were more concentrated during T2 when the subjects were dehydrated compared to all other tests. This was true both when tested before and after exercise. No other statistically significant results were observed for the range of hormonal and biochemical markers tested.



The researchers concluded that AG supplementation “provided a significant ergogenic benefit by increasing time to exhaustion during a mild hydration stress. This ergogenic effect was likely mediated by an enhanced fluid and electrolyte uptake.”


Our Comments

With so many different forms of glutamine on the market it is nice to see a study supporting the usage of a particular type. L-Alanyl-L-Glutamine has shown promise in the past for increasing hydration and electrolyte absorption greater than the effects of glutamine alone (2) and this study shows a similar story.

The researchers themselves proposed that given the T4 group still performed significantly better in their exercise test without showing any significant increase in glutamine concentration, that the mechanism behind the performance improvement was likely via L-Alanyl-L-Glutamine’s ability to facilitate greater uptake of fluids and electrolytes through the gut. They proposed further that enhanced glutamine uptake via the muscles could result in greater uptake of sodium also (which was borne out in the studies showing lower concentrations of sodium in the supplemented trials). This would also help with performance during endurance activity by reducing muscle fatigue.

It would be interesting to see how this type of glutamine worked in an environment where carbohydrates were provided. To help isolate the effects of compounds studies will commonly provide nutrients to subjects in a fasted state. The possibility that this would influence the outcome cannot be dismissed. Having said that, given the potential hormonal and body composition advantages proposed for training while fasted, the usage of L-Alanyl-L-Glutamine could well help increase performance for those who regularly engage in fasted training such as intermittent fasting or those who practise morning cardio to help shed body fat.


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Further Reading

BCAAs + Glutamine useful even when protein intake is high


Author: Reggie Johal



1. Examination of the efficacy of acute L-alanyl-L- glutamine ingestion during hydration stress in endurance exercise Hoffman JR, et al. J Int Soc Sports Nutr. 2010 Feb 3;7:8.

2. Lima AA (2002): Effects of an alanyl-glutamine-based oral rehydration and nutrition therapy solution on electrolyte and water absorption in a rat model of secretory diarrhea induced by cholera toxin.

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