Protein is having a moment. And it should, given the vast array of functions it plays in the body. When we think of protein, we consider building muscle and optimizing metabolism. However, protein is also vital for overall gut health. Protein metabolites not only feed our gut bacteria, but they also play pivotal roles in supporting immunity and strengthening our defenses.

First, some brief physiology - when we consume dietary proteins, they are broken down into amino acids during the process of digestion. Optimal chewing and strong stomach acid support this process. These amino acids are then absorbed by the small intestine and transported to tissues and organs, including the gut, where they are utilized for various functions.

Role #1: Gut Barrier Function

Amino acids are crucial for maintaining the integrity of the gut barrier. The gut barrier acts as a protective fortress that prevents harmful substances, such as pathogens and toxins, from entering the bloodstream. The gut barrier is formed by specialized cells lining the intestinal walls, and amino acids are essential for the repair and regeneration of these cells.

Glutamine is one of the most abundant amino acids in the body. It is a primary fuel source for the cells lining the intestinal walls, supporting their rapid turnover and promoting gut barrier integrity. Glutamine also helps maintain the structure and function of tight junction proteins, which is critical for the selective permeability of the gut barrier.

Proline is another essential amino acid that plays a significant role in producing collagen and other connective tissues. Collagen helps maintain the structural integrity of the gut lining and supports tissue repair in cases of injury or inflammation.

Role #2: Mucin Production

Mucins are glycoproteins that form a protective layer of mucus in the gut lining. This mucus layer acts as a physical barrier against pathogens and aids in the smooth passage of food through the digestive tract. Mucins contain various amino acids, especially cysteine, threonine, and proline, essential for their structure and function. Balance can be important, as one study noted that a deficiency and also excess of dietary threonine can reduce intestinal mucin synthesis.

Role #3: Gut Microbiota Support

Amino acids play a role in shaping the composition of the gut microbiome. Some amino acids serve as energy sources for beneficial gut bacteria, promoting their growth and proliferation. In turn, these beneficial bacteria produce short-chain fatty acids (SCFAs) through fermentation of amino acids, which have numerous benefits for gut health, such as reducing inflammation and supporting the immune system and gut barrier.

Role #4: Immune System Support

The gut houses a significant portion of the body's immune system. What’s fascinating is that within the intestinal immune system, there are regional specializations. The small intestine protects the ability of the surface cells to digest and absorb food while also preventing it from infection. The large intestine houses trillions of microorganisms. While recognizing their importance, it keeps them at arm’s length through the production of thick mucosal layers, antibodies, and immune T cells. Amino acids are involved in the production of these immune cells and antibodies, helping to strengthen the gut's immune defenses against pathogens and infections.

Role #5: Gut Motility

Some amino acids, such as glutamine, arginine, and glycine, are involved in regulating gut motility. Proper gut motility ensures the timely movement of food through the digestive tract, promoting efficient digestion and absorption of nutrients.

Role #6: Neurotransmitter Production

Amino acids also play a role in synthesizing neurotransmitters, such as serotonin and dopamine, which are essential for regulating gut motility, mood, and overall gut-brain communication.

Amino acids are essential for various aspects of gut health, including digestion, gut barrier function, mucin production, gut microbiota support, immune system function, gut motility, and neurotransmitter production. Consuming a balanced diet that provides a variety of protein sources can ensure an adequate supply of amino acids to support optimal gut health and overall well-being.

References:

Beaumont, M., & Blachier, F. (2020). Amino Acids in Intestinal Physiology and Health. Advances in experimental medicine and biology, 1265, 1–20. https://doi.org/10.1007/978-3-030-45328-2_1

Mowat, A., Agace, W. Regional specialization within the intestinal immune system. Nat Rev Immunol 14, 667–685 (2014). https://doi.org/10.1038/nri3738

Yang, Z., & Liao, S. F. (2019). Physiological Effects of Dietary Amino Acids on Gut Health and Functions of Swine. Frontiers in veterinary science, 6, 169. https://doi.org/10.3389/fvets.2019.00169

https://www.frontiersin.org/articles/10.3389/fnut.2022.1066898/full