Irritable bowel syndrome (IBS) is one of the functional bowel disorders meaning there is no visible structural abnormality in the gut or change in the blood tests, but there is a disruption of the normal functions of the gut (peristalsis or the movement, sensitivity of the nerves in the gut and how the brain controls it). Because of that, recently, these disorders have obtained the name Disorders of gut-brain interaction. 

In IBS, symptoms such as 

• lower abdominal pain, 

• distention (increase in the circumference of belly), 

• bloating (feeling of pressure, tension), 

• recurring diarrhea or constipation, or both

• excessive flatulence 

have a chronic course and can affect the life quality significantly. It is estimated that up to 9% of the population worldwide is affected by it! But a lot of people experiencing it, especially on the milder side, do not seek help. 

However, a low FOODMAP diet with the proper supervision of a dietitian can bring a relief of the symptoms up to 80% of patients with IBS, We will explore the low FOODMAP diet in the next post.

Remember that some occasional bloating and flatulence can be normal, however, if you experience the symptoms above weekly, it may be time to visit a gastroenerologist and dietitian trained in this. 

We acquire our initial gut microbiota at birth, and it evolves with us, influenced by our habits, diet, environment, genetics, medication, and social interactions. Just as you are shaped by the people around you, so is your microbiota.

Why is the microbiota important?

• Immune system training: About 70% of immune cells are in the gut, evolving alongside the microbiota, which trains and maintains the immune system.

• Pathogen Defense: A healthy microbiota protects against harmful microorganisms.

• Gut Function: It plays a crucial role in gut functionality.

• Metabolite Production: Gut microorganisms produce metabolites, including vitamins and short-chain fatty acids, vital as an energy source for the cells of your gut.

• Health reflector: Microbiota composition can provide an insight into overall health & there are often similarities among people with the same health conditions. 

The current understanding is that the ratio of human cells to microbiota cells is 1:1, not 1:10 as previously thought. However, this still represents a vast number of microorganisms, predominantly inhabiting the large intestine, though present in the small intestine as well. Most people have around 100-200 different stable microorganisms in their gut.

The microbiota includes bacteria, fungi, viruses, protozoa, and archaea, with Firmicutes (e.g., lactobacilli), Bacteroidetes, and Actinobacteria (e.g., bifidobacteria) being predominant. A healthy balance among these groups is crucial for a well-functioning ecosystem.

Caring for Your Microbiota: Most of the beneficial bacteria thrive on soluble and insoluble fiber, found in vegetables, fruits, and whole grains. Providing a consistent supply of fiber keeps your microbiota healthy.

Additional Notes:

• Microbiome: Refers to the gene pool of the microbiota.

• Dietary Changes: When altering your diet, it takes a few weeks for the microbiota to adapt. Gradually introduce fiber-rich foods to avoid digestive discomfort. Cooking these foods can also help.

You may have heard that the gut is sometimes referred to as the second brain. This is because there is a nervous system in your gut too. It's called the enteric nervous system (ENS), and it is well connected with the central nervous system (CNS) in your brain. The communication goes both ways; there are top-down and bottom-up pathways delivering information from the brain to the gut and vice versa.

This bilateral communication is involved in appetite and energy homeostasis, glucose metabolism, immune regulation, regulation of emotions, stress response, and other processes. Both the so-called efferent (top-down) and afferent (bottom-up) communication are carried out via:

I The bloodstream

II The nervous system

There are three main players in the nervous system here:

• The vagus nerve, which stretches from the brain all the way to the gut

• Spinal neurons, which are responsible for innervating the gut

• The ENS, which can also act independently in the gut

The communication can be rather direct, via the vagus nerve or it can be mediated by the ENS, which then communicates with the vagus nerve.

Instead of words, these two parties communicate with different compounds as chemical signals, including:

• Neurotransmitters

• Intestinal hormones, also called gut peptides

• Cytokines

• Microbiome-derived metabolites

While neurotransmitters are the primary language of the nervous system, intestinal hormones can both travel to the brain through the blood or activate neurons. Additionally, physical signals, such as the stretching of the intestines, are communicated to the brain.

In bottom-up communication, these signals are released in response to the contents of the gut lumen. So, yes, what you eat can and will affect what the gut is "telling" your brain!

The gut can be viewed at multiple levels, each of which serves distinct functions.

I The intestines provide a long, lined tube that allows for increased time and surface area for nutrient absorption as they pass through.

II The intestinal wall is composed of four main tissue layers:

• Mucosa

• Submucosa

• Muscularis (muscular layer)

• Serosa (serous layer) 

These layers prevent damage, ensure motility, facilitate connection with the brain, establish links to the circulatory system, and serve as sites for absorption and secretion.

III The cells located at the interface of the inner lining of the gut are specialized in carrying out various functions. Some produce digestive enzymes, secretions, and gut peptides, while others act as gateways for the digested nutrients to enter the bloodstream.

There is another important barrier mechanism, located in the brain. It ensures that not everything absorbed and circulating in the blood can reach the sensitive brain cells (neurons) and affect them.

The main elements of the brain barrier are: 

I Astrocytes (selective support cells) 

II Endothelium (blood vessel cells with tight junctions)

This means that not everything we consume with hopes it could affect the brain actually can reach it. Gases, water-soluble compounds, and only small fat-soluble compounds are absorbed through it. For example, glucose, amino acids, and fatty acids are welcome.

However, similarly to the gut, dysfunction of this barrier can also occur.

Although the digestive tract is located in the gut, its interior technically separates the organism from the outside. Therefore, it needs protection by a gut barrier that determines what can and cannot enter the body. This barrier is crucial because of the active digestion and absorption processes in the intestine, as well as fermentation in the later stages.

The gut barrier consists of four layers, each providing a level of protection and its own functions: 

I Microbial barrier (natural microflora) 

II Chemical barrier (mucus) 

III Physical barrier (cells with tight junctions) 

IV Immune barrier (immune cells)

One consequence of barrier dysfunction is that the body is no longer protected against compounds and pathogens that normally wouldn't get past it. This is referred to as increased permeability of the intestinal barrier, commonly known as 'leaky gut'.

Increased permeability may be linked to diseases with a chronic inflammatory course, both in the intestinal tract and elsewhere in the body. Disturbances have been observed in patients with ADHD, depression, Alzheimer's, Parkinson's disease and other conditions. Although the causality is still not clear (chicken or egg), increased permeability of the barrier cannot go without consequences.