The gut, our second brain: explanations?

Doctor in Human Movement Sciences, Mélanie and Jérôme Vaulerin from Monaco Care Concept explain the link between the intestine and the brain.

The intestine, our second brain: explanations?

Due to its complexity, the intestine has similarities with the brain, and is thought to contain more than 200 million neurons. This enteric nervous system communicates closely with the central nervous system via hormonal secretions (dopamine and serotonin) which are essential to our mental health. Some everyday expressions such as "having a knotted stomach", "fear in the stomach" or "digesting information" take on their full meaning. Indeed, when people are stressed, they often feel abdominal pain and do not feel well. The stress felt sends signals from the brain to the intestines, causing sudden contractions similar to muscle cramps called spasms, even leading to episodes of diarrhoea. Numerous studies show that there is a real link between the brain, emotions and the intestine. Indeed, an imbalance of the intestinal microbiota (see Article October 2019) would have consequences on the psychological state of individuals: depression, anxiety, neurodegenerative diseases (Parkinson, Alzheimer). In a way, the intestinal microbiota is the brain's informant.

Serotonin: the feel-good hormone

The digestive system is rich in neural transmissions and plays an important role in the production of serotonin (the good mood hormone). Serotonin is a neurotransmitter in the brain that acts to transmit information between neurons. Studies have shown that 95% of the serotonin in the body is produced in the gut and then transmitted to the brain. This hormone regulates brain activity by influencing mood, sleep, appetite, motivation, decision-making, stress and depression. But that's not all, it is also involved in the functioning of the intestinal microbiota, the contraction of the intestine and digestion. Serotonin is a fundamental hormone for the proper functioning of the body. There are many causes of serotonin deficiency; a poor diet leads to a deficiency in tryptophan, the precursor of serotonin; stress and lack of sunlight negatively influence the production of serotonin in the brain. A serotonin deficiency could lead to an increased risk of depression, anxiety, mood disorders, panic attacks, or mental exhaustion. Some symptoms are easily detected: headaches, sleep disorders, concentration problems, reduced feeling of satiety, muscle pain. If there is any doubt, it is important to check the serotonin level by means of a hormonal blood test.

Feeding your microbiota for a healthy brain

What we eat determines our mental health. The quality of food plays a fundamental role in the composition and activity of the intestinal microbiota. Indeed, it is important to favour foods rich in dietary fibre (at least 55 grams per day), vitamins and minerals such as fruit and vegetables to facilitate digestion and limit the development of certain chronic diseases (cancers). In addition, plant foods (legumes, wholegrain cereals, dried fruit, fruit and vegetables) are rich in prebiotics, which are the real fuel for the bacteria in the microbiota, and help to maintain good intestinal harmony. Fermented foods (soya, kefir) and dairy products (yoghurt with active bifidus) contain bacteria that are favourable for the microbiota. Finally, foods rich in polyphenols (red fruits, grapes, soy, green or black tea) have a positive effect on the microbiota. Polyphenol is a powerful antioxidant that protects the body from bacteria and other parasites. All of these foods help us to have a good transit and keep our brain in shape.