If you’ve searched for gut health supplements, then chances are L-glutamine was a top suggestion. Glutamine, the body’s most abundant amino acid, is used by skeletal muscles, the GI tract, kidneys, immune cells, and more. Glutamine is the primary fuel source for enterocytes – the cells that make up the inner surface of the intestines. In fact, the gut uses more glutamine than any other system in the body, and the small intestines make up the bulk of that use.

So, what are the enterocytes doing with all that glutamine? Tissue integrity, including regulating intestinal barrier function, is one of glutamine’s major roles. Enterocytes use it as an energy source to do their work, including cellular repair and proliferation. The cells that line the intestinal barrier are constantly under assault – digesting food, absorbing nutrients, eliminating waste, and resisting toxins. This results in considerable wear and tear on these tissues, which is why these cells are regenerated every 4-5 days; this constant turnover requires significant nutrient support.1  

The gut barrier consists of a special type of connection between cells, called tight junctions, which allows for the proper absorption of substances, such as water, nutrients, and ions into the mucosal tissues and blood, while restricting the movement of pathogens and toxins. When the enterocytes and tight junctions become damaged – from use, illness, stress, etc. – increased intestinal permeability can be the result.

Increased Intestinal Permeability – aka “Leaky Gut”

Commonly referred to as “leaky gut,” increased intestinal permeability can play a negative role in autoimmune and inflammatory diseases.2 Clinical studies show that a lack of glutamine in the small intestine, whether from insufficient intake or increased needs by other tissues due to illness, injury, or intense exercise, can lead to decreased thickness of the small intestinal lining and a resultant increase in intestinal permeability.3

Leaky gut can also be a concern for athletes. Increased exercise intensity causes the demand for glutamine by skeletal muscles to increase, decreasing the available glutamine in the body’s total amino acid pool and leaving the intestines and other glutamine-dependent tissues to compete for what remains.

With high-intensity endurance exercise, like distance running, the diversion of blood flow to skeletal muscles and to essential organs like the brain and heart leads to a lack of blood and oxygen in the intestines. This can also be a cause of damage to the gut barrier, leading to increased intestinal permeability and accompanying adverse gastrointestinal symptoms.4

Glutamine and Gut Immune Function

Glutamine also plays a role in immune function and inflammatory response in the gut.* Approximately 70-80 percent of immune cells reside in the GI tract, and many immune cells – like fibroblasts, lymphocytes, and macrophages – use glutamine as metabolic fuel. Glutamine helps regulate inflammatory signaling pathways, including nuclear factor kappa beta (NF-kβ), which can increase production of inflammatory cytokines – namely IL-6 and TNF-α – and over-stimulate the immune response.1

Glutamine can positively affect the gut microbiome as well.* A 2015 clinical trial tested whether supplementation with L-glutamine could alter the gut microbiome in adults with overweight and obesity issues. The experimental group received glutamine daily for 14 days while the control group received the amino acid alanine. The group who received glutamine experienced a statistically significant reduction in the ratio of Firmicutes-to-Bacteroidetes bacterial species while the ratio increased in the alanine group. A higher ratio is associated with obesity and is considered a less desirable microbial composition for health.5

Dietary Sources of Glutamine

By now you might be wondering, “Where does glutamine come from?” Glutamine is classified as a “conditionally-essential” amino acid, meaning your body can make the glutamine it needs under normal conditions, but increased demands, such as with illness, exercise, or stress, make the body dependent on external sources to maintain its glutamine pool. Food sources of glutamine are often those that are high in protein, like beef, chicken, fish, eggs, and dairy products. Bone broth is an easy-to-digest source of glutamine that is also high in vitamins, minerals, and essential fatty acids. Plants are good sources of glutamine, too. Beans, beets, cabbage, spinach, carrots, kale, and whole grains all provide dietary glutamine.

In supplement form, L-glutamine is available as a powder or in capsules. Gut health-supportive formulas, like Thorne’s EnteroMend, provide multi-nutrient support for a healthy intestinal lining, normal inflammatory response, and immune function in the GI tract.* If you’re interested in learning more about your gut microbiome and its role in your overall health, check out Thorne’s Gut Health Test.

For more on glutamine, read these articles available at Take 5 Daily:

  1. Top 3 Reasons to Add Glutamine to Your Recovery Plan
  2. Are You an Athlete Who Suffers from Leaky Gut?
  3. 8 Foods and Drinks That Promote Gut Health

References

  1. Kim MH, Kim H. The roles of glutamine in the intestine . . . . Int J Mol Sci 2017;18(5):1051. doi:10.3390/ijms18051051
  2. Ulluwishewa D, Anderson RC, McNabb WC, et al. Regulation of tight junction permeability by intestinal bacteria and dietary components. J Nutr 2011;141(5):769-776. doi:10.3945/jn.110.135657
  3. Bischoff SC, Barbara G, Buurman W, et al. Intestinal permeability . . . . BMC Gastroenterol 2014;14:189. doi:10.1186/s12876-014-0189-7
  4. Ribeiro FM, Petriz B, Marques G, et al. Is there an exercise-intensity threshold capable of avoiding the leaky gut? Front Nutr 2021;8:627289. doi:10.3389/fnut.2021.627289
  5. de Souza AZ, Zambom AZ, Abboud KY, et al. Oral supplementation with L-glutamine alters gut microbiota of obese and overweight adults: A pilot study. Nutrition 2015;31(6):884-889. doi:10.1016/j.nut.2015.01.004