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WORDS Belinda Reynolds

Glutamine is the most abundant amino acid in the body and is of paramount importance for overall health. Training at high intensities has been found to deplete available glutamine levels in the body, and low concentrations have been noted in athletes experiencing significant discomfort from overtraining. 1,2

Sportspeople often think of glutamine as a supplement for muscle protein synthesis, repair and growth - and for good reason. Glutamine, along with the branched chain amino acids (BCAAs) make up a large component of muscle protein mass. Its benefits, however, go far beyond this. Not only does glutamine assist the formation of other amino acids (e.g. L-arginine), it plays fundamental roles in energy production, the clearance of “fatigue factors” from the blood during training (e.g. ammonia, phosphorous) and regulating acid-base balance, to enhance performance 1,3. It also supports immune function 4, reduces exercise-induced inflammation, and maintains intestinal health in athletes 1,5. In a 2008 trial, when glutamine (3.5g) was given together with maltodextrin (50g) half an hour before exercise, and results compared with maltodextrin alone, the blend was proven to be superior. Subjects on the mixture showed a greater increase in the distance covered during an exercise test. The blend also led to an increase in the length of time for which the intermittent exercise was tolerated, and athletes experienced reduced feelings of fatigue, all when compared to maltodextrin alone 6. These results are believed to be due to glutamine’s role in the krebs cycle (a key energy-producing process in the body), and a resultant ability of glutamine to enhance the efficiency of metabolic processes. Glutamine also appears to increase a process known as gluconeogenesis in the liver that maintains glucose and glycogen availability to working muscles.

More recent trials have further supported glutamine’s role in enhancing performance, with a carbohydrate plus glutamine combination proving superior in prevention of decreases in anaerobic power, thus improving athletic physical performance (2). Interestingly in this paper, the glutamine and carbohydrate combination was superior in efficacy to both carbohydrate alone and glutamine alone, supporting the importance of incorporating multiple essential components of performance and recovery into a training program 2.

In addition to enhancing performance, glutamine can also reduce undesirable effects that high-intensity training can exert on the body, which compromise recovery and overall health if not addressed. It has been found that increases in the permeability of the intestinal lining develop from heavy exercise. The result is gastrointestinal discomfort, an increased passage of unwanted molecules into the body, and thus a worsened internal inflammatory state, slower recovery, compromised future performance and poorer resistance to infection. As glutamine is used as a key energy source for fuelling repair of the intestinal tract, it’s no surprise that glutamine supplementation is shown to prevent this exercise-induced increase in gut permeability and the resultant release of inflammatory mediators in the body 5. This has significant implications not only for supporting your ongoing training, but health in general.

High-intensity training also sees the accumulation of certain compounds in the muscles and blood (e.g. phosphorous, lactate and ammonia). These contribute to pain, diminished ability to perform at your peak, and premature exhaustion (e.g. ammonia interferes with cellular ATP synthesis), therefore approaches which minimise their build-up are useful.

A small trial found that at 6g per day for seven days, glutamine was able to reduce blood phosphorous (which can decrease power) during the recovery stage after maximal intensity exercise. Creatine kinase (a marker of tissue damage) was also reduced, plus the glutamine supplementation attenuated increases in inflammatory markers 1. An additional preliminary trial found that glutamine supplementation (at 100mg per kg of body weight) helped to protect against undesirable exercise-induced increases in ammonia 3.

In conclusion, although more research is warranted, glutamine appears to be a useful addition to the training protocol of sports people, not just in the recovery stages, but also taken prior to training and for preventative reasons.

1. Koo GH, Woo J, Kang S, et al. Effects of Supplementation with BCAA and L-glutamine on Blood Fatigue Factors and Cytokines in Juvenile Athletes Submitted to Maximal Intensity Rowing Performance. J Phys Ther Sci 2014;26(8):1241-1246.
2. Khorshidi-Hosseini M, Nakhostin-Roohi B. Effect of glutamine and maltodextrin acute supplementation on anaerobic power. Asian J Sports Med 2013;4(2):131-136.
3. Bassini-Cameron A, Monteiro A, Gomes A, et al. Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way. Br J Sports Med 2008;42(4):260-266.
4. Cruzat VF, Krause M, Newsholme P. Amino acid supplementation and impact on immune function in the context of exercise. J Int Soc Sports Nutr 2014;11(1):61.
5. Zuhl M, Dokladny K, Mermier C, et al. The effects of acute oral glutamine supplementation on exercise-induced gastrointestinal permeability and heat shock protein expression in peripheral blood mononuclear cells. Cell Stress Chaperones 2015;20(1):85-93.
6. Favano A, Santos-Silva PR, Nakano EY, et al. Peptide glutamine supplementation for tolerance of intermittent exercise in soccer players. Clinics (Sao Paulo). 2008;63(1):27-32.

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