Glutamine
Overview:
Glutamine, an amino acid that is found naturally in a variety of food sources is considered a “conditionally essential” amino acid, as it is only essential given its benefits in repairing the muscular deterioration after a traumatic event like a serious injury or disease. The supplement is commonly found in large amounts in meat and eggs, as it exists in significant concentrations in both whey and casein proteins. While it is required in large amounts to achieve a ‘surplus’, Glutamine is consumed so frequently, due to its abundance in meats, eggs, milk and other every-day foods, that its required level of supplementation is minimal in most cases.
Benefits:
While efficacy is still being examined, it appears that glutamine is a useful contributor to protein synthesis in active individuals operating with a sub-optimal level of glutamine, as studies have demonstrated a link between glutamine levels and anabolic activity. A ‘surplus’ results in muscle growth, while a ‘deficit’ results in catabolism (references 1,2,3), therefore inferring that a surplus is desirable. Additionally, glutamine has been seen to improve ease of longer-duration cardiovascular activity (reference 6) and improve muscle glycogen stores in the absence of carbohydrates (reference 7) and therefore provide utility for individuals using diets comprised of limited carbohydrate intake (such as the popular keto diet).
Side-Effects:
The “Observed Safety Limit” of Glutamine intake (the most you can consume without experiencing side-effects) is to the tune of 14g/day of excess supplementation (in excess of what is consumed naturally through the diet) and otherwise no negative side-effects have been documented as statistically significant or dangerous (reference 8). Limited studies show that when consuming .75g/kg of bodyweight (a 175lb person would be consuming nearly 60g/day), there may be increases in plasma ammonia levels (reference 9), but these are well above the doses suggested below.
Synergies:
Glutamine has not been shown to enhance the effects of other supplements in studies to date (references 4,5).
Dosage:
As described above, Glutamine is found naturally in large amounts across the average diet. Supplementation can be anywhere from 1g to 5g, leaning more toward the lower end due to larger consumption being unnecessary in excess of healthy individuals’ diets.
Further Reference:
1. Ward E, et al Oral glutamine in paediatric oncology patients: a dose finding study . Eur J Clin Nutr. (2003)
2. Shao A, Hathcock JN Risk assessment for the amino acids taurine, L-glutamine and L-arginine . Regul Toxicol Pharmacol. (2008)
3. Bowtell JL, et al Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exercise . J Appl Physiol. (1999)
4. Carvalho-Peixoto J, Alves RC, Cameron LC Glutamine and carbohydrate supplements reduce ammonemia increase during endurance field exercise . Appl Physiol Nutr Metab. (2007)
5. Lehmkuhl M, et al The effects of 8 weeks of creatine monohydrate and glutamine supplementation on body composition and performance measures . J Strength Cond Res. (2003)
6. Wilkinson SB, et al Addition of glutamine to essential amino acids and carbohydrate does not enhance anabolism in young human males following exercise . Appl Physiol Nutr Metab. (2006)
7. MacLennan PA, et al Inhibition of protein breakdown by glutamine in perfused rat skeletal muscle . FEBS Lett. (1988)
8. MacLennan PA, Brown RA, Rennie MJ A positive relationship between protein synthetic rate and intracellular glutamine concentration in perfused rat skeletal muscle . FEBS Lett. (1987)
9. Zhou X, Thompson JR Regulation of protein turnover by glutamine in heat-shocked skeletal myotubes . Biochim Biophys Acta. (1997)