Glutamine is a type of amino acid naturally found in the human body. This conditionally essential amino acid is known for supporting intestinal and immune system health. In periods of disease and muscle wasting, it becomes an essential amino acid.
It has two different forms: L-glutamine and D-glutamine. These forms are almost identical but have slightly different molecular arrangements. L-glutamine is found in foods and supplements and is employed to synthesize proteins and perform other functions. D-glutamine, on the other hand, seems relatively unimportant in living organisms.
Glutamine plays a crucial role in immune function. During periods of illness or injury, the body may not produce enough of it, making glutamine supplements useful for boosting immune function and preserving protein stores. Glutamine also serves as an energy source for intestinal and immune cells, helping maintain the barrier between the intestines and the rest of the body and promoting the proper growth of intestinal cells. 
While there is limited evidence for using glutamine supplements for muscle gain or strength performance, they may help reduce fatigue and decrease muscle soreness during and after exercise.
Additionally, some studies have found that taking glutamine with other nutrients, including vitamins C and E, beta-carotene, selenium, and N-acetylcysteine, can result in weight gain and improved nutrient absorption in people with HIV and AIDS. Endurance athletes have also experienced reduced infection rates while taking glutamine supplements.
Those with liver and kidney disease or Reye syndrome should avoid consuming glutamine. Additionally, people with a history of psychiatric disorders or seizures should exercise caution when considering glutamine supplements, as they may exacerbate these conditions. Older adults with reduced kidney function may need to adjust their glutamine dose.
L-glutamine naturally comes from the diet, but if you prefer to take a supplement, a healthy dosage ranges from 3 to 6 grams daily. According to a paper in Regulatory Toxicology and Pharmacology, a safe amount for healthy people is 14 grams; for children, it is no more than 0.7 grams daily per kilogram of body weight.
L-glutamine supplements are sold in powder, capsule, and tablet form at health food stores, pharmacies, grocery stores, and online.
You can take l-glutamine at any time of the day. If you want to optimize your workouts and lessen the onset of fatigue, consider taking it 30 minutes before, during, and immediately after vigorous activity.
It is crucial to keep glutamine supplements in a dry location and avoid adding the powder to hot beverages, as heat can destroy it.
1. Durani S. (2008). Protein design with L- and D-alpha-amino acid structures as the alphabet. Accounts of chemical research, 41(10), 1301–1308. https://doi.org/10.1021/ar700265t
2. van Zanten, A. R., Dhaliwal, R., Garrel, D., & Heyland, D. K. (2015). Enteral glutamine supplementation in critically ill patients: a systematic review and meta-analysis. Critical care (London, England), 19(1), 294. https://doi.org/10.1186/s13054-015-1002-x
3. Demling R. H. (2009). Nutrition, anabolism, and the wound healing process: an overview. Eplasty, 9, e9.
4. Wang, B., Wu, G., Zhou, Z., Dai, Z., Sun, Y., Ji, Y., Li, W., Wang, W., Liu, C., Han, F., & Wu, Z. (2015). Glutamine and intestinal barrier function. Amino acids, 47(10), 2143–2154. https://doi.org/10.1007/s00726-014-1773-4
5. Legault, Z., Bagnall, N., & Kimmerly, D. S. (2015). The Influence of Oral L-Glutamine Supplementation on Muscle Strength Recovery and Soreness Following Unilateral Knee Extension Eccentric Exercise. International journal of sport nutrition and exercise metabolism, 25(5), 417–426. https://doi.org/10.1123/ijsnem.2014-0209
6. Glutamine. (n.d.). Mount Sinai - New York. Retrieved March 21, 2023, from https://www.mountsinai.org/health-library/supplement/glutamine
7. Shao, A., & Hathcock, J. N. (2008). Risk assessment for the amino acids taurine, L-glutamine and L-arginine. Regulatory toxicology and pharmacology : RTP, 50(3), 376–399. https://doi.org/10.1016/j.yrtph.2008.01.004