Our gut is our second brain, more and more people are now familiar with this idea. But, actually our gut is even more than that and research keeps discovering new roles of the bacteria populating our intestines. By sending messages via our nerves, blood flow and immune system, our gut bacteria (microbiota) influence a broad range of basic functions such as our sleep, stress level, mood, memory…. In one sentence: our gut governs our existence.

Our gut controls our mood, our anxiety level, and our sociability

It has been established by countless research papers that people suffering from depression, anxiety, or autism were also suffering from gastrointestinal issues. In an experiment, rats deprived of their gut microbiota showed more anxiety and less sociability than the control group. More interesting, when the bacterial flora of the control group was removed and given to the experimental group, their behaviors exchanged between each other as well! In humans, taking probiotics has shown to decrease cortisol (the stress hormone) level in the saliva.

Our gut controls our immune system

Some bacteria actually control our immune system’s response to fight other bacteria. This may seem counter-intuitive based on the belief that bacteria are “bad”, however there are “good” bacteria that help to strengthen our immune system.  This starts as soon as we are born and it perpetuates later in life. A recent study showed that a certain bacteria produces a substance that raises the production of our CD4+ T cells, which play an important role in our immune response. This explains why the increase in sanitation and using anti-bacterial products in recent decades has correlated with increase food sensitivities and environmental allergies, especially in children.

Our gut regulates our biological clock and our sleep cycle

In my previous post I talked about the circadian rhythm, which controls the alteration of our resting and waking phases. A recent study showed that the circadian rhythm was altered with rats lacking microbiota. Why? In order to sleep well, we need appropriate amounts of melatonin, which is the sleep hormone. Our body needs serotonin in order to produce melatonin, and 95% of our serotonin is synthetized in our….gut.

Our gut influences our mental clarity and our memory

In 2015, a study showed that rats with a diet poor in fiber and rich in saturated fats/sugars presented with altered microbiota. Interestingly, a month later the rats with the same poor diet started to show slower performance times when given memory and cognitive tests.

Our gut influences our heredity

Statistics show that we tend to have more hereditary traits from our mother than our father. For instance kids with an obese mother will have a higher probability to become obese than if their father was obese. A study has noted that mouses with a diet poor in fibers would cause increased risk in obesity. But interestingly those mouses’ offspring would develop obesity persisting throughout the rest of their lives. Even though this hasn’t been fully proven yet, it is very likely that natural delivery and breast feeding is crucial for the development of good microbiota of the children, and their immune system. This shows the importance of vaginal delivery versus c-section and breast feeding versus baby formula.

It controls our weight and nutrient absorption

Researchers were able to demonstrate that a poor microbiota caused poor absorption from the energy coming from the dietary fibers, and it altered the production of vitamins B and K, essential for cell growth and blood coagulation. Furthermore, a poor micobiota showed to increase the body fat percentage, even with a calorie-restricted diet.

Our gut drives our appetite and what we like to eat

Do you love chocolate? Well, the real question should be : does your gut bacteria love chocolate? When we eat, the bacteria in our gut produce substances that promote the production of leptin (the satiety hormone) and ghrelin (the hunger hormone). In other words, our bacteria can make us feel cravings for foods that they like. In an evolutionary perspective, the reason why bacteria are capable of influencing our hunger is because they’re promoting their own growth. Some bacteria grow better with sugar, others prefer alcohol, and the best way to grow is to force their host (us) to feed them with those types of foods. Another reason to stay away from sugar and alcohol!

It determines how quickly we age.

As we get older, our microbiota become less stable and less diverse. This can be explained by the fact that the elderly are eating fewer varieties of food. But researchers are now not sure if poor micorbiota is a cause or a consequence of getting old. As our gut gets older, we lose the ability to produce essential fatty acids and vitamins which accelerate inflammation and oxidation processes.

A new age of medicine

Now that we have a better understanding on how much influence our gut has on us, we can appreciate how harmful today’s environment is for our bodies. Those years of eating crappy food has screwed us up quite a lot. Depression, autoimmunity, allergies, obesity, mental disorders, chronic fatigue, low grade energy…those are the result of years and years of torture to our gut.
Another enemy is the overuse of antibiotics. Of course medication has been a huge progress in medicine and has saved countless lives from infections, but antibiotics will kill ALL bacteria without discrimination, good or bad.  Think twice the next time you get sick. There are several strategies and methods to naturally improve gut health:


Avoid processed food, sugar (of ANY form), saturated fat. Eat organic, local. Use anti-inflammatory diet such as AIP(autoimmune Paleo), Mediterranean diet,…

– Stool analysis

This test is more powerful than genetic testing. The latter allows to identify risk factors of some disorders, but there is nothing we can do to modify a gene. A stool analysis will not only provide a lot of information about health risk factors (sometimes more than a gene test, for instance for obesity), but moreover it allows to TAKE ACTION by re-balancing the microbiota and hence treat numerous diseases.

– Use probiotics and prebiotics

Usually taken as natural supplements, probiotics help to repopulate the gut with the beneficial bacteria. Prebiotic is the food that good bacteria need, hence taking prebiotics will speed up their proliferation in our gut.

– Fecal microbiota transplant (FMT)

Kind of extreme, but it works. It’s basically what it sounds like… a transplant of fecal matter from a healthy person into the gut of an unhealthy one.


The gut is highly correlated to so many different non-specific or long term disorders. Whether you are seeking relief from chronic pain, optimization of performance, or need answers to your health issues, make sure your doctor carefully checks your gut function.


This article is a summary of the article “Les super-pouvoirs du ventre”, published by Science et Vie Magazine N. 1183 (April 2016) by E. Abdoun with K. Bettayeb, F. Gracci and H. Rambert.

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