Should You Consider Taking Glutamine?
Written by Calvin Sun

Along with creatine and BCAAs, L-glutamine is one of the most popular yet misunderstood supplements in the fitness industry. I often get questions from clients and readers about the function of glutamine, the benefits it can provide, and its proper usage. The purpose of today’s article is to answer some of these common questions and provide you with enough information to decide whether or not glutamine should be a part of your supplement regimen.

What Is Glutamine?

Glutamine is one of the naturally occurring amino acids found in dietary protein and is one of six considered to be a conditionally essential amino acid. While these amino acids are typically in adequate supply, they become conditionally essential when stress, illness, trauma, or other conditions create a need that exceeds its current availability. In other words, glutamine often becomes conditionally essential in athletes because the rate of depletion exceeds the rate of replenishment from the body’s own synthesis and intake from dietary food sources. Research has found that over-trained athletes have depleted levels of glutamine compared to healthy, well-trained athletes [1, 5]. Glutamine supplementation can be useful for a variety of applications.

Why Should I Consider Glutamine?

Glutamine has several benefits including improved immune function [1,2], improved glycogen replenishment after intense exercise [3,4], healing of the gut [6,8,9], and it can even help curb cravings for sweets.

Immune Function

Glutamine plays an essential role in the proliferation of lymphocytes, a type of white blood cell that plays an important role in normal immune function [1]. Other research has found that depleted glutamine levels appear to have a correlation with diminished immune function [2]. If you have ever engaged in an intense, high-volume training cycle and found yourself more susceptible to colds and other illness, it’s possible that depleted glutamine levels may have played a role. Anecdotal evidence from our own pool of athletes suggests that taking glutamine during these training cycles can help improve immune function and reduce the risk of getting sick during competition season.

Gut Repair

Research has found that glutamine can assist in healing and repair of the gut lining. One animal model study compared glutamine, glycine, and untreated control groups of mice that had undergone irradiation of their gastrointestinal tract. Researchers found that while both glycine and glutamine helped with repair, glutamine proved to have superior results with regard to healing and repair of the gut lining [9].

Increased intestinal permeability (also referred to as “leaky gut syndrome”) is a problem that can lead to autoimmune disorders such as rheumatoid arthritis, Hashimoto’s thyroiditis, lupus, psoriasis, and celiac disease. Depression, anxiety, migraine headaches, muscle pain, and chronic fatigue are all possible indicators that you might have a leaky gut. Glutamine supplementation can help with repair of the gut lining and reduce the permeability of the intestines. Of course, if you suspect that you might have leaky gut syndrome or might have an autoimmune disorder, it’s best to consult with a medical professional who specializes in treating these types of conditions. You’ll likely need to remove foods from your diet that cause gut irritation, as well as take other supplements, like probiotics, to assist in restoring your gut health.

Recovery For Athletes

Research has found that the intramuscular concentration of glutamine is correlated with the rate of net protein synthesis [3]. There is also research that suggests glutamine can help promote replenishment of glycogen stores after intense exercise. In one study published in the Journal of Applied Physiology, researchers compared glucose-only, glutamine-only, and glucose combined with glutamine protocols in athletes who had their glycogen stores depleted. Researchers found that glutamine consumption post-workout resulted in a 25% increase in glycogen synthesis rates compared to the glucose-only group [4].

Reduce Sugar Cravings

If you’re trying to kick your sugar habit, glutamine supplementation might be helpful for dealing with those sweet cravings. Expert coaches, like Charles Poliquin, often recommend 1 to 2 grams of glutamine in water before meals to help reduce carbohydrate intake or 2 to 10 grams to help curb cravings. In my experience, this method has worked very well for my nutrition coaching clients. While I couldn’t find any peer-reviewed studies that directly studied glutamine and its role in sugar cravings, other research can help provide a scientific basis for why it works.

In the aforementioned study published in the Journal of Applied Physiology, the ability of glutamine to regulate glycogen synthesis and glucose production might explain why oral supplementation can help reduce sugar cravings. If these cravings are the result of low plasma concentrations of glucose, glutamine can serve as precursor to glucose in gluconeogenic pathways [11] and, in turn, reduce activation of the hypothalamus which results in increased feelings of satiety and fullness [12].

How Do I Take Glutamine?

If you are trying to repair and heal your gut, you can mix 5 grams of glutamine in water and consume on an empty stomach to help facilitate repair of the epithelial lining of the gut. This procedure can be repeated throughout the day between meals as needed. If you are an athlete looking to improve net protein synthesis, immune function, and glycogen replenishment, the scientific literature has found that 8 to 10 grams of glutamine to be an effective dose. I would suggest adding your glutamine to your post-workout shake for best results. If you are focused on fat loss, you can try using 2 to 5 grams of glutamine mixed in water or in capsule form to help curb sweet cravings throughout the day.

Can I Take Too Much Glutamine?

The upper limit for dosage mentioned in most scientific literature is 0.65 grams per kilogram of bodyweight. For a 150 pound person, that’s about 44 grams of glutamine in a day. In the research I cited for this article, human test subjects took up to 30 grams a day with no acute adverse effects.

Is There A Brand You Recommend? 

I like NOW Foods L-Glutamine Powder and BulkSupplements Pure L-Glutamine Powder. It’s very affordable at less than 19 cents per 5 gram serving. If you prefer capsules, I suggest Thorne Research L-Glutamine Capsules. I have personally used each of these brands and recommend them to my clients and athletes.

Based on current research and anecdotal evidence from our own clients, glutamine is a safe and effective supplement for gut health, immune function, recovery for athletes, and curbing sugar cravings. If you’re interested in learning more about effective supplementation, stay tuned to the blog as we will be releasing our new book on the subject in February 2017.

Still have a question about glutamine? Feel free to post below in the comments.

References:
1. Gleeson, M. Dosing and Efficacy of Glutamine Supplementation in Human Exercise and Sport Training. J. Nutr. October 2008, vol. 138 no. 10 2045S-2049S.
2. Soeters PB, Grecu I. Have we enough glutamine and how does it work? A clinician’s view. Ann Nutr Metab. 2012;60(1):17-26. doi: 10.1159/000334880. Epub 2011 Dec 30.
3. Rennie MJ, Edwards RH, Krywawych S, Davies CT, Halliday D, Waterlow JC, Millward DJ. Effect of exercise on protein turnover in man. Clin Sci. 1981;61:627–39.
4. Bowtell JL, Gelly K, Jackman ML, Patel A, Simeoni M, Rennie MJ. Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exercise. J Appl Physiol. 1999;86:1770–7
5. Antonio J, Street C. Glutamine: a potentially useful supplement for athletes. Can J Appl Physiol. 1999 Feb;24(1):1-14.
6. Kozar RA, Schultz SG, Bick RJ, Poindexter BJ, DeSoignie R, Moore FA. Enteral glutamine but not alanine maintains small bowel barrier function after ischemia/reperfusion injury in rats. Shock. 2004;21:433.
7. T C Welbourne. Increased plasma bicarbonate and growth hormone after an oral glutamine load. Am J Clin Nutr May 1995. vol. 61 no. 5 1058-1061.
8. Quan ZF, Yang C, Li N, Li JS. Effect of glutamine on change in early postoperative intestinal permeability and its relation to systemic inflammatory response. World J Gastroenterol. 2004;10:1992–4.
9. Diestel CF1, Marques RG, Lopes-Paulo F, Paiva D, Horst NL, Caetano CE, Portela MC. Role of L-glutamine and glycine supplementation on irradiated colonic wall. Int J Colorectal Dis. 2007 Dec;22(12):1523-9. Epub 2007 Aug 10.
10. Simpson CW1, Resch GE, Millington WR, Myers RD. Glycyl-L-glutamine injected centrally suppresses alcohol drinking in P rats. Alcohol. 1998 Aug;16(2):101-7.
11. Nunes Santiago A1, de Godoi-Gazola VA, Fachin Milani M, de Campos VC, Rodrigues Vilela V, Diaz Pedrosa MM, Bazotte RB. Oral glutamine is superior than oral glucose to promote glycemia recovery in mice submitted to insulin-induced hypoglycemia.
12. Page KA, Chan O, Arora J, Belfort-Deaguiar R, Dzuira J, Roehmholdt B, Cline GW, Naik S, Sinha R, Constable RT, Sherwin RS. Effects of fructose vs glucose on regional cerebral blood flow in brain regions involved with appetite and reward pathways. JAMA. 2012 Jan 2;309(1):63-70. doi: 10.1001/jama.2012.116975.

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