Glutamine Functions and Benefits for Your Microbiome

What is glutamine?

Glutamine is one of the 20 naturally occurring amino acids that the body uses to make protein, and serves as an energy source for muscle. Glutamine is a conditionally essential amino acid, meaning that during periods of illness, heavy exercise or stress, the body cannot make enough and supplementation may be necessary.

What foods contain glutamine?

Glutamine is found in a number of foods including:

Foods that contain glutamine | ThinkBiome
  • Beef
  • Eggs
  • Milk
  • Spinach
  • Cabbage
  • Tofu
  • Corn
  • Parsley

Glutamine is sensitive to heat and cooking may result in degradation. Thus, glutamine is often taken as a supplement in the biologically available form of L-Glutamine.

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Glutamine and the Microbiome

Why is glutamine so important for your microbiome?

Two reasons:

  1. Intestinal permeability
  2. Bacterial metabolism

The cells of the intestine (called enterocytes) form a selective barrier that lets essential things like dietary nutrients and water in, and keeps everything else out. Disruption of this barrier due to stress, infection or immunological challenges causes increased gut permeability (called “leaky gut”) and is associated with multiple diseases, such as food allergies, inflammatory bowel disease, celiac disease, irritable bowel syndrome, and type I diabetes.

Glutamine is the main energy source for these cells and plays many essential roles in the normal functioning of a healthy intestine. These roles include helping to keep the cells together, stopping them from dying unnecessarily when stressed, preventing bacteria from sticking to the intestinal wall and providing building blocks (protein synthesis) for healing. Basically, glutamine helps maintain a healthy environment for your gut microbiome.

This is borne out when looking at the changes in intestinal bacteria after supplementing L-glutamine. There are four major families of bacteria that have been identified in the gut microbiome:

  1. Firmicutes
  2. Bacteroidetes
  3. Actinobacteria
  4. Proteobacteria

The most studied of these are the Firmicutes and Bacteroidetes. It’s worthy to note here that hunter-gatherer tribes (where allergies and immune system diseases are almost non-existent) have very few Firmicutes in their gut microbiomes.

In animal studies glutamine supplementation positively affects the Firmicutes to Bacteroidetes ratio (increases the number of Bacteroidetes). The reason for this is not currently known. Glutamine supplementation affects how amino acids are metabolized by the gut microbiome, which ultimately affects the products those bacteria make. For example, supplementing glutamine causes some bacteria in the gut microbiome to stop (or at least decrease) their utilization of glutamate and for other bacteria to increase their production of glutamate. This is significant because glutamate has important functions in the body (such as muscle building and supporting brain function). This type of change alters the local environment of the gut, which may favor the growth of the Bacteroidetes family of bacteria.

The Firmicutes/Bacteroidetes ratio is a good biomarker for obesity, where the number of Firmicutes is higher than Bacteroidetes. This knowledge led one research group to study the effects of glutamine supplementation in obese individuals. They found that supplementing with 30g of glutamine per day over a two-week period altered the gut microbiome of overweight and obese individuals. This lowered the Firmicutes to Bacteroidetes ratio, which resembled published weight-loss programs. Now this doesn’t mean that an overweight person can simply start taking a glutamine supplement and magically lose weight, but is a great example of how glutamine can alter the composition of the human gut microbiome in a beneficial manner.

How much should someone supplement?

L-Glutamine is available orally in powder, capsule and liquid form. The dosing varies greatly depending on the reason for supplementation. Doses range from 5 – 30g per day based on the premise of taking 0.3g of glutamine per kilogram of bodyweight.

L-Glutamine is generally well tolerated, but taking more than 0.75g per kg bodyweight (51g for a 150lb person), has been shown to increase ammonia levels in the blood. People with kidney or liver disease should not take glutamine due to the metabolites produced, however the amounts found in food are safe to consume.

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Reading List

Arrieta MC, Bistritz L, Meddings JB (2006) Alterations in intestinal permeability. Gut 55:1512–1520.

Camilleri M, Madsen K, Spiller R, Greenwood-Van Meerveld B, Verne GN (2012) Intestinal barrier function in health and gastrointestinal disease. Neurogastroenterol Motil 24:503–512.

Dai et al., (2013) L-Glutamine regulates amino acid utilization by intestinal bacteria. Amino Acids. 45:501-512 DOI 10.1007/s00726-01201264-4.

Groschwitz KR, Hogan SP (2009) Intestinal barrier function: molecular regulation and disease pathogenesis. J Allergy Clin Immunol 124:3–20.

Ren et al., (2014) Dietary L-Glutamine supplementation modulates microbial community and activates innate immunity in the mouse intestine. Amino Acids. DOI 10.1007/s00726-014-1793-0.

Wang et al., (2015) Glutamine and intestinal barrier function. Amino Acids 47:2143–2154 DOI 10.1007/s00726-014-1773-4.

Zambom de Souza, et al. (2015) Oral supplementation with l-glutamine alters gut microbiota of obese and overweight adults: A pilot study. Nutrition. Volume 31:6 pp884 – 889.