The unexpected risks of an unbalanced intestinal microbiota

Cancer, diabetes, Alzheimer's disease, fibromyalgia... so many illnesses that could be explained by imbalances in the gut microbiota.

From obesity to depression, from cancer to fibromyalgia, the gut microbiota, long ignored or underestimated, is now at the forefront of research to prevent the onset of often severe, chronic, and sometimes incurable diseases.

The billions of bacteria that inhabit our digestive tract play a crucial role in many diseases... often in unexpected ways.

Discover these diseases that, although they seemingly have nothing to do with the digestive system, are at least partly induced by imbalances in the gut microbiota.

What is the gut microbiota?

The microbiota refers to all microorganisms - bacteria, viruses, parasites, non-pathogenic fungi - that live in a specific environment. In our body, there are different microbiotas, such as those on the skin, in the mouth, in the vagina... The gut microbiota is the most important of these, with 10^12 to 10^14 microorganisms. That's 2 to 10 times more than the number of cells that make up our body, weighing about 2 kilograms!

This gut microbiota is mainly located in the small intestine and the colon (the gastric acidity making the stomach wall almost sterile).

Although its existence was discovered over a century ago, the means to study it remain limited, and it is only very recently that we have begun to understand the crucial functions it performs in the body.

It is now established that beyond its digestive functions alone, it plays a role in the metabolic, immune, and neurological functions of our body.

This explains why the gut microbiota and its dysfunction called "dysbiosis" can be the cause of a large number of diseases and are a major avenue for prevention.

The dangers of an imbalanced gut microbiota

Instinctively, it is easy to understand that an imbalance in the gut microbiota can be responsible for digestive disorders ranging from simple transient diarrhea to inflammatory bowel diseases (IBD) including irritable bowel syndrome.

We are less aware that this imbalance can have various and often significant consequences.

Obesity and diabetes

On a metabolic level, the gut microbiota plays a role as an additional organ in a way at least equivalent to that of the liver!

Metabolism defines all the coupled reactions that occur naturally in the cells of the body. It consists of two opposite mechanisms:

• Catabolism: it allows the extraction of energy from nutrients in our diet, by breaking down energy molecules (carbohydrates, lipids, proteins...);
• Anabolism: it allows the synthesis of the constituents necessary for the structure and proper functioning of cells.

When this metabolism malfunctions, many so-called "metabolic" diseases occur.

We now know why an imbalanced gut microbiota contributes to promoting some of these diseases.

• Obesity: the decrease in one variety of bacteria (Bacteroidetes) coupled with the increase in another (Firmicutes) could lead to a propensity for the microbiota to more easily store the energy provided by the diet. This would thus have a consequence of an increased risk of obesity. It has also been observed that with equal weight loss diets, individuals with a greater bacterial variety in the gut microbiota experience more significant weight loss than those with less rich bacterial strains. And this remains the case after the diet is stopped, during the stabilization phase.

• Type 2 diabetes: the gut microbiota plays an essential role in insulin resistance and thus in maintaining normal blood sugar levels. Type 2 diabetes is precisely a disease characterized by insulin resistance resulting in too high blood sugar levels. Moreover, studies conducted on diabetic patients have shown that most patients had a significant decrease in bacteria producing butyrate and an increase in opportunistic bacteria causing chronic inflammation.

While the causes of obesity and type 2 diabetes are multiple (dietary habits, sedentary lifestyle, etc.), the gut microbiota pathway is an interesting risk factor and would explain the disparities between individuals with the same lifestyle and whether or not they develop these pathologies.

Cancers

It is now considered that the microbiota intervenes in carcinogenesis, that is, the process leading to the formation of cancer.

A number of studies conclude that certain tumors are linked to the presence of specific microorganisms or even dysbiosis in the intestinal tract.

It is established, for example, that an imbalance in the gut microbiota in favor of certain species (fusobacterium) would increase the risk of colorectal cancer, or that the presence of Helicobacter pylori favors the occurrence of gastric cancer.

Some studies also point to a correlation between regular intake of antibiotics (which disrupt the balance of the gut microbiota) in young women and the occurrence of breast cancer.

More broadly, it seems that some good bacteria in the gut microbiota play a role in certain cancers by controlling the genes of our cells. Chemical messages from these bacteria would be able to change the location of certain chemical markers within the human genome.

Depression, anxiety, schizophrenia

We all know the saying that our gut is our second brain. This is only partly true, but it is now commonly accepted that the functioning of the human brain is influenced by the gut microbiota, and this, very early on.

This is because the nervous system that governs the intestine alone contains 200 million neurons. Its primary function is to ensure intestinal motility; however, 

80% of these nerve cells transmit information from the intestine to the brain. Thus, an imbalance in the gut microbiota may modify the information transmitted to the central nervous system.

Some preliminary studies now mention dysbiosis as a risk factor for depression and anxiety among other genetic, epigenetic, environmental, and psychological factors. Thus, imbalances in the gut microbiota have been observed in anxious or depressed patients. Researchers have been able to perform fecal microbiota transplants between anxious mice and non-anxious mice. After this exchange, the anxious mice were cured of their disorders, while the non-anxious mice showed obvious signs of anxiety.

One hypothesis is that certain bacteria play a role in the proper functioning of neurotransmitters and thus contribute to disrupting the mental balance. This is a major avenue considering that it is estimated that in France nearly one in five people will suffer from depression during their lifetime and that 6% of French people are affected by generalized anxiety disorder.

In individuals with schizophrenia or bipolar disorders, it has been noted that the balance between different cytokines (substances produced by the immune system) pro-inflammatory or anti-inflammatory in the blood is disturbed. However, these cytokines are directly mediated by substances present on the surface of certain bacteria, themselves naturally present in the gut microbiota.

These avenues open up quite formidable prospects in terms of therapeutic management and may one day significantly reduce the intake of anxiolytics, antidepressants, neuroleptics, and antipsychotics by using probiotics and an adapted diet.

Alzheimer's disease, Parkinson's disease

More recently, it has been realized that the microbiota may play a role in the development of neurodegenerative diseases such as Alzheimer's or Parkinson's diseases.

It could indeed be involved in the process of brain inflammation linked to Alzheimer's disease causing the serious cognitive decline that we know. Researchers have also been able to demonstrate that an adapted diet - rich in probiotics and anti-inflammatory agents - can slow the progression of the disease by combating intestinal permeability.

As for Parkinson's disease, the severity of its symptoms appears to be correlated with the concentration of a particular species of bacteria (enterobacteriaceae) in the gut microbiota. The various phenomena explaining these two degenerative diseases could be mediated by neuroactive substances of bacterial origin.

While in France Parkinson's disease affects more than 200,000 people and Alzheimer's disease affects more than one million patients, with only symptomatic treatments available with heavy side effects, the first studies on the microbiota open up more than interesting therapeutic prospects.

Chronic fatigue, fibromyalgia

Persistent fatigue, muscle pains, headaches, or even memory problems are symptoms that characterize chronic fatigue. A disabling syndrome whose origins were until now poorly understood and for which there is no treatment.

However, recent studies have established a link between chronic fatigue and dysbiosis. Indeed, it seems that the gut microbiota of people suffering from this syndrome has a higher concentration of certain bacteria than in people who do not suffer from it. Researchers explain that individuals with chronic fatigue syndrome have a distinct mix of intestinal bacteria and related metabolic disorders that can influence the severity of their illness. This implies a sort of "breakdown" in communication between the brain and the gut governed by bacteria.

Regarding fibromyalgia, increasing intake of prebiotics and probiotics to rebalance the gut microbiota helps reduce pain (often extremely severe) and fight inflammation.

Faced with these chronic diseases for which symptoms can only be partially relieved and which leave patients in a certain despair, the gut microbiota pathway is more than interesting and deserves to be given its due importance.

Asthma and respiratory allergies

Asthma remains a chronic disease today. While it sometimes seems to disappear in adolescence, it can always return unexpectedly in adulthood. There is currently no curative treatment.

But, for about ten years now, researchers have been discussing the role of the microbiota in terms of both prevention and treatment.

Four types of intestinal bacteria would indeed play a major role in the prevention of asthma. Their acquisition in the first hundred days of life would protect newborns against this disease. A study showed that young patients had a deficiency in four bacteria (Faecalibacterium, Lachnospira, Veillonella, and Rothia) that are normally naturally acquired by infants.

In addition, Australian researchers have recently established a link between fiber supplementation (inulin, a soluble fiber, to be precise) that stimulates the gut microbiota and reduces asthma attacks as well as respiratory tract inflammation. Another study shows that oral intake of a specific antibiotic that modifies the composition of the gut microbiota reduces symptoms in severe asthmatics in adulthood.

While respiratory allergies affect more and more people, a link has been established between an imbalance in the gut microbiota, influencing immunity very early on, and seasonal allergies. It seems that increased exposure to antibiotics from childhood, disrupting the balance of the microbiota, reduces the effectiveness of type 2 immunity, precisely that which regulates our ability to fight allergens causing respiratory conditions.

How to take care of your gut microbiota?

In order to give yourself every chance of staying healthy for a long time, it is essential to maintain a varied and balanced gut microbiota. Taking good care of it prevents many ailments in a simple, inexpensive, and non-medicated way.

Nutrition

Our diet itself plays an important preventive role in having a healthy gut microbiota.

Here are some tips to effectively stimulate it, preserve its diversity, and proper functioning:

• Eat fiber: Intestinal bacteria feed on fiber (prebiotics), so it is beneficial to increase intake in the form of whole grains, legumes (lentils, chickpeas, white beans, flageolets, split peas), vegetables (especially asparagus, artichoke, leek, garlic, onion, peas, cabbage...), and fruits (especially passion fruit, banana, berries).
• Avoid additives: Sweeteners in processed foods increase the levels of Bacteroides and Clostridiales bacteria, altering metabolic functions, which increases insulin resistance and contributes to diabetes and obesity. Emulsifiers cause intestinal inflammation, altering satiety signals sent to the brain.
• Think about fermented foods. Fermented foods (kimchi, kombucha, miso, sauerkraut), dairy products (kefir, yogurt, cheese) are rich in live microorganisms that enrich the microbiota.
• Opt for gentle cooking. Steam cooking increases the digestibility of fiber.
• Choose the right fats. Prefer cold-pressed virgin oils, raw: camelina oil, walnut oil, rapeseed oil, linseed oil... Also consider fatty fish (salmon, tuna, sardines, mackerel). Omega-3s play an important role in the composition and metabolic activity of the microbiota.

Consume foods rich in glutamine. Glutamine is an amino acid that helps restore intestinal barrier integrity. You will find it in fish, eggs, dairy products, cabbages, parsley...

• Limit meat consumption: Animal fat-rich foods increase the proportion of Bacteroides and Firmicutes bacteria that produce metabolites. These promote local inflammation leading to a loss of sensitivity of the vagus nerve to satiety signals sent to the brain, resulting in less appetite regulation. It is better to opt for low-fat proteins (fish, soy derivatives, legumes).
• Consume sugar in (great) moderation. Refined industrial sugar, as well as chemical sweeteners, disrupt the intestinal flora in favor of harmful fungi like Candida Albicans;
• Avoid alcohol

Probiotics

After taking antibiotics, intestinal infection, unbalanced meals such as during holidays, heavy consumption of alcohol or tobacco, periods of stress, or any other situation impacting the intestinal flora, it is essential to restore your gut microbiota.

To do this, start with L-Glutamine, which helps strengthen the integrity of the intestinal mucosa, and probiotics.

Probiotics will have three major actions:

1. They will modulate the activity of the intestinal immune system. They enhance immunity when it is weak and reduce the overactivation of the immune system, especially in cases of allergies or intestinal inflammation.

2. They will increase the barrier function of the intestinal mucosa.

3. They will have direct anti-microbial effects by replacing pathogenic bacteria and preventing their adhesion to the intestinal walls.

Thus, they will allow the microbiota to regain its diversity in "good bacteria" useful to the body and help it fight against excess bad bacteria that interfere with the proper functioning of our immune system, metabolism, as well as the digestive neurons/brain neurons loop.

After an initial one-month course, it is recommended to follow a maintenance course with one to two doses per week and to supplement with probiotics when you are in a "high-risk" period.

Finally, remember that the primary cause of microbiota disruption is antibiotic use. Only take them when absolutely necessary, on the prescription of your doctor - no swallowing them for a simple cold!