Written by Isabel Amir with Amanda Forman

Did you know that that April is IBS Awareness Month? in 1997 IFFGD, the International Foundation for Gastrointestinal Disorders, designated April as IBS Awareness Month. If you have irritable bowel syndrome (IBS), you are not alone – IBS is common with prevalence estimated at 5% to 10% worldwide, and many of our patients. Yet many people remain undiagnosed and unaware that their symptoms indicate a medically recognized disorder.

What is the Gut Microbiome?

When you think of the gut microbiome what do you picture? Just like an ecosystem, which has living components such as plants, animals, and fungi/bacteria, and environmental components such as soil, air, and light, the gut microbiome also has components such as fibers and bacteria. Just as all of the components in the ecosystem work symbiotically,  and can either contribute to the health or destruction of the ecosystem, so too do the components of the gut contribute to a healthy gut or gut dysfunction.  Preparing the soil with nourishment lays the foundation for a vibrant garden, or if your soil is laden with heavy metals or chemicals that can disrupt the healthy bacteria the soil and garden can suffer. Fiber and optimal growth of good bacteria strains, act as the fertilizer for your gut and lay the foundation for your gut to function more efficiently. On the flip side, if nutrient dense foods are scarce and excessive foods that are inflammatory or intolerances/allergies are present and consumed, you may have gastrointestinal symptoms and upset the balance in your own ecosystem.

The human body contains trillions of various microorganisms (i.e. microbiota and microbes) The “microbiome” is a collection of all the microbes—bacteria, fungi, viruses—that occur naturally in and on our bodies. These microbiomes are found in various locations in and on the body: the skin, mouth, nasal cavity, and, most well-known, the gut. The majority of the gut microbiota reside in the colon, or the large intestine. The gut microbiome plays a pivotal role in our overall health and has been referred to as the “second brain” for this reason.

The Function of the Gut Microbiome

DIGESTION 

The bacteria in the gut help break down food such as carbohydrates and fiber, especially. By breaking down fiber—found in complex carbohydrates like fruits, oats, whole grains, beans/legumes—the gut produces substrates called short-chain fatty acids (SCFAs). These include acetate, propionate, butyrate, valerate. The SCFAs act as food for our gut to help maintain the gut lining, anti-inflammatory properties, proper metabolism of food/nutrients, and regulate the immune system.

METABOLISM, HUNGER, & SATIETY

The gut microbiota interacts with the various endocrine cells in the lining of the gut. For this reason, the gut is known as the largest endocrine organ of the body. The gut secretes hormones that help regulate your metabolism, hunger and satiety, and blood sugar. Cholecystokinin (CCK) is a gut-derived peptide hormone that plays a role in satiety. This is what allows you to feel full and satisfied from your meals! CCK is produced and released by cells in the small intestine. It interacts with another satiety hormone, known as leptin, to reduce food intake. Peptide YY (PYY) and glucagon-like peptide 1 (GLP1) are other satiety hormones that are also secreted by the small intestine. These hormones are released from the small and large intestines in response to consumption of carbohydrates, protein, and fat. A healthy gut will be able to effectively produce all of these hormones to regulate intake. GLP1 also plays a role in regulating blood sugar level, which is important in lowering the risk of developing diabetes. Gastric inhibitory polypeptide (GIP) is a hormone produced by cells in part of the small intestine, and released in response to meals/carbohydrates. GIP stimulates insulin release, which is the hormone that helps to reduce blood sugar by transporting it into cells. Like GLP1, GIP helps with overall blood sugar regulation.

IMMUNITY / INFLAMMATION 

Did you know the gut contains up to 80% of the body’s immune cells? The gastrointestinal tract (GIT) is the site of interaction between microorganisms and the immune system and plays a crucial role in maintaining healthy immune responses.  The gut microbiome benefits the immune system by defending the body against pathogens. Without the appropriate microorganisms, the immune system fails to be properly developed, making the individual more susceptible to sickness.

The gut microbiota regulates the immune system by regulating the inflammatory response. It plays a pivotal role in the development of the CD4+ T cells—a type of white blood cell (WBC) that helps coordinate the cells and mechanisms of the innate immune system. CD4+ T cells play a role in the adaptive immune system and can differentiate into four subtypes upon stimulation: T helper 1 (Th1) cells protect against intracellular microbial infections; Th2 cells protect against parasites; Th17 cells mediate defensive mechanisms to control infection; Treg cells regulate the immune response. The regulation of these T cells and balance between pro-inflammatory cytokines with the anti-inflammatory mechanisms relies on signals from the gut bacteria, which are dependent on the composition of the gut microbiome. Proper functioning of the CD4+ T cells is crucial to maintaining effective immune and inflammatory responses.

MOOD/COGNITION 

There has been much talk recently about the gut/brain connection. The gut is a main site of neurotransmitter production. These neurotransmitters are sent and received by neurons (i.e. brain cells), indicating a link between the gut and the brain. These organs communicate via a network known as the gut-brain axis. Given the connection of these organs, research has linked gut health and microbiome composition to cognitive function and mental health. An imbalance of the composition of the gut microbiota, known as dysbiosis, has been linked to various cognitive disorders including dementia, Alzheimer’s disease, autism, bipolar disorder and obsessive-compulsive disorder, in addition to depression and anxiety. Individuals with disorder of the GIT, like inflammatory bowel disease, are at a greater risk of these mental health conditions/cognitive disorders.

How to Promote a Healthy Gut

The single most important factor in maintaining a healthy composition of gut microbiota is to eat a diet rich in color and fiber. Incorporating a variety of plants (i.e. whole grains, beans/legumes, fruits, and vegetables) will provide the gut with an abundance of fiber to feed the microbes. Probiotics are live microorganisms that confer a health benefit to the host (i.e. you) when consumed in adequate amounts. Probiotics can be found in fermented foods like cultured yogurt, kimchi, sauerkraut, tempeh, kombucha, and pickled vegetables. They can also be helpful in maintaining a healthy community of gut microorganisms. Prebiotics are foods that feed our probiotics in the gut,  such as artichokes, onions and garlic to name a few, which enable the production of those SCFAs. Prebiotics are an important component of the diet for this reason, as the SCFAs maintain anti-inflammatory and immunoregulatory mechanisms. Consuming a variety of colorful plant foods will ensure we are providing the gut with diverse foodstuffs to promote a more diverse microbiome composition.

As you can see the gut microbiome is extremely important when it comes to your health and well-being. Here at Real You Nutrition we always focus on food first as consuming a balanced diet and a variety of foods should provide your body with all the nutrients it needs to maintain an efficient and healthy gut microbiome, and enhance your health.  We also use the GIMAP when we want to dig deeper into the balance, health and wellness of the gut.

References

 https://www.niehs.nih.gov/health/topics/science/microbiome

 https://www.hsph.harvard.edu/nutritionsource/microbiome/

https://my.clevelandclinic.org/health/body/25201-gut-microbiome

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10196242/#:~:text=Most%20SCFAs%20function%20in%20the,organs%20(4%2C%205).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7147657/

https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1098386/full

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3337124/#:~:text=The%20gut%20microbiota%20that%20resides,dysregulation%2C%20leading%20to%20autoimmune%20disorders.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3312336/#:~:text=The%20CD4%2BT%20cells%20carry,the%20suppression%20of%20immune%20reaction.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6469458/#:~:text=The%20gut%2Dbrain%20axis%20is,routes%20of%20communication%20as%20well.

https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-brain-gut-connection

https://www.optum.com/en/health-articles/article/healthy-mind/surprising-link-between-your-microbiome-and-mental-health/