Picture this!.. You are in front of your computer screen and you see that something sad and stressful has happened somewhere in the world and you, in turn, feel sad and stressed… Immediately afterwards, you see a picture of a character eating an ice cream and suddenly you get a pleasant feeling that brings you relief from your stress. What happened here? Why do certain foods produce a cascade of pleasant emotions in us? Behind this, there is something emotional and mental going on, something that goes beyond the functional and that helps us explain the relationship between the intestinal microbiota and the brain.
The gut-brain axis is an increasingly studied system that explains why your mood can be affected by what you eat or drink. When the digestive and nervous systems work in harmony they can provoke positive mental and physical reactions. We now know that the health of the gut microbiota can influence reduced stress, improved cognitive function, greater emotional balance and better sleep. In the past, scientists considered the brain to be the most important organ when it comes to mental health. However, more and more evidence is beginning to reveal the importance of gut health. It is estimated that 90% of all mental health problems have a connection to what happens in our intestines.
WHY IS THE INTESTINE CONSIDERED THE SECOND BRAIN?
The gut-brain axis is a communication link between the gut and the brain. It includes four main pathways that allow the brain and digestive system to send and receive signals to each other. These are the connection routes:
- Neuroendocrine pathway – This pathway is the communication between the hypothalamus and the gastrointestinal tract. The hypothalamus, the part of the brain responsible for emotions and motivation, receives cognitive and behavioural signals that affect hormones and gut symptoms.
- Autonomic nervous system – This pathway transmits signals from the brain to the organs of the digestive system that control digestion and is responsible for processes related to digestion, such as the production of digestive enzymes and the speed of the digestive process.
- Immune response – This pathway determines how the body reacts to specific foods, bacteria, or viruses within the digestive system and how the body communicates those reactions to the brain. It is responsible for maintaining the balance between the immune system and the rest of the body since an imbalance (intestinal dysbiosis) can cause digestive problems.
- Enteric nervous system – Lastly, the enteric nervous system connects the neurons of the gastrointestinal tract to the brain and is responsible for the digestion of food, absorption, and secretion of digestive juices into the gastrointestinal tract.
WHICH ILLNESSES SHOW A GUT-BRAIN CONNECTION?
Depression and anxiety are possibly two of the most common mental health problems associated with an altered gut-brain axis. Studies have found that an unbalanced gut microbiota can affect the hippocampus – responsible for regulating mood – resulting in increased anxiety and depression.
As Professor Ted Dinan and his colleagues from University College Cork (Ireland) explain in the latest issue of the journal Neurogastroenterology & Motility, several recent studies show that in animal models, depression and anxiety are related to an alteration in the composition of the intestinal microbiota.
Understanding the relationship between emotions and the microbiota could lead to the development of “new treatments for a wide variety of pathologies including obesity, mood disorders and gastrointestinal ailments”, concludes Professor Dinan.
Research by gastroenterologist Premysl Bercik, from McMaster University (Canada), also supports these ideas. In experiments with mice, Bercik verified that, after modifying the composition of the microbiota of specimens that had a passive behaviour pattern, they changed their “personality” (exploratory behaviour), became more exploratory and tended to seek novelty and risk. Blues Bacteria or How the Microbiota Can Affect Mood – Gut Microbiota for Health
In 2019, a macro study was published with more than a thousand patients in which the composition of the intestinal microbiota is correlated with quality of life and depression. The researchers found that the butyrate-producing bacteria Faecalibacterium and Coprococcus were consistently associated with indicators of good quality of life. On the other hand, Dialister and Coprococcus bacteria were decreased in people with depression. (Valles-Colomer, et. al, 2019) In a second study parallel to the previous one, the intestinal microbiota and its relationship with depressive symptoms were characterized in six ethnic groups (Dutch, South Asian Surinamese, African Surinamese, Ghanaian, Turkish and Moroccan) from the same urban area (the city of Amsterdam). , in a total of 3,021 people. The results confirmed those obtained in the previous work, and showed that the intestinal microbiota linked to depressive symptoms was independent of ethnic group.
In 2019, a macro study was published with more than a thousand patients in which the composition of the intestinal microbiota is correlated with quality of life and depression. The researchers found that the butyrate-producing bacteria Faecalibacterium and Coprococcus were consistently associated with indicators of good quality of life. On the other hand, Dialister and Coprococcus bacteria were decreased in people with depression. (Valles-Colomer, et. al, 2019) In a second study parallel to the previous one, the intestinal microbiota and its relationship with depressive symptoms were characterized in six ethnic groups (Dutch, South Asian Surinamese, African Surinamese, Ghanaian, Turkish and Moroccan) from the same urban area (the city of Amsterdam), in a total of 3,021 people. The results confirmed those obtained in the previous work and showed that the intestinal microbiota linked to depressive symptoms was independent of ethnic group.
HOW TO IMPROVE BRAIN AND GUT COMMUNICATION
The importance of treating disorders of the gut-brain axis is increasing in light of recent research: with gut health linked to mental health, it is increasingly crucial to understand and treat problems related to the gut-brain axis.
GABA, SEROTONIN AND OTHER NEUROTRANSMITTERS
Gamma-aminobutyric acid (GABA) is a very common amino acid in brain neurons. It is believed to calm neurons and protect our brain against stimulus overload, which is why it has been linked to reducing stress and improving sleep.
Research has revealed the role that the microbiota plays in GABA production. The prestigious journal Nature reported that the production of GABA by bacteria reduces pain by acting on sensory neurons in the stomach. Another article, published in the same journal, revealed a link between depression and the relative abundance of bacteria that synthesize and degrade this neurotransmitter.
CHANGE! PREBIOTICS AND OTHER TIPS
- Prebiotics: Prebiotics are a type of fibre that stimulates the growth of healthy bacteria. Among the foods rich in prebiotics are artichokes, bananas, mushrooms such as Lion’s mane (its standardized organic extract contains GABA), Shiitake or Pleurotus, asparagus, oats and apples.
- Varied foods: This can lead to a diverse microbiome, which is an indicator of good gut health. In particular, legumes, beans and fruit contain a lot of fibre and can support the growth of healthy bifidobacteria.
- Worst: Red Meat: Red meat can trigger the growth of gut bacteria that lead to clogged arteries. Stick to lean protein sources such as fish or plant protein like beans and tofu. If you can’t give up beef, pork, and lamb completely, choose leaner cuts with names that include round, loin, or sirloin.
- Fried Foods: Fried foods are already on the not-good-for-you list. It hasn’t been proven in humans yet, but studies on rats show that heated oil, which soaks into fried foods, can damage healthy gut bacteria.
- Foods With Antibiotics: Antibiotics can’t tell the difference between “good” and “bad” bacteria, so they kill them all. Often, farmers treat animals with antibiotics to keep them from getting infections. If you eat these animal products, you can kill the healthy bacteria in your gut. And because some bacteria become antibiotic resistant over time, meaning the drugs no longer affect it, you might end up with a hard-to-kill superbug.
- Alcohol: Alcohol, especially if you’re a heavy drinker, can disrupt the balance of bacteria in your gut and help bad bacteria grow. Moderation is key.
- Caffeine: Coffee, soda, and even too much chocolate can up the caffeine in your body, which ramps up your intestines. This excitement in your digestive system often causes diarrhoea.
- Fermented foods: Fermented foods like yoghurt, sauerkraut, and kefir contain healthy bacteria, primarily lactobacilli, and can reduce the number of disease-causing species in the gut.
- Whole Grains: our body can’t break down fibre on its own. When it gets to your large intestine, gut bacteria get to work fermenting it. This creates acids that feed cells in your intestines while helping to protect your gut from harmful bacteria.
- Polyphenols: These compounds in foods protect your cells from damage while fighting inflammation and infection. Colourful foods are rich in polyphenols, as are tea, coffee, and red wine. Polyphenols in green tea may help fight “bad” bacteria like E. coli and calm symptoms of inflammatory bowel disease (IBD) and peptic ulcers. Polyphenols can also promote the growth of good gut bacteria.
- Limit your exposure to stress: Uncontrolled stress can damage the gut-brain axis, as it can cause damage to both the neurons in the gut and the hippocampus of the brain.
- Releases the happiness hormone: Regular exercise promotes the release of endorphins, which can help improve mood and reduce stress levels, as well as increase the amount of beneficial bacteria in the gut.
- A good rest: Poor sleep can have a detrimental effect on mental health and damage the gut-brain axis.
- Avoid artificial sweeteners: Some tests have shown that artificial sweeteners such as aspartame increase blood sugar by stimulating the growth of unhealthy bacteria such as Enterobacteriaceae in the gut microbiome.
REFERENCES
Melancholic microbes: a link between gut microbiota and depression? – PubMed (nih.gov)
Gut bacteria linked to behavior: That anxiety may be in your gut, not in your head | ScienceDaily
The gut microbiota and depressive symptoms across ethnic groups | Nature Communications
http://download.journals.elsevierhealth.com/pdfs/journals/0016-5085/PIIS0016508511602308.pdf
https://www.nature.com/articles/s41564-018-0337-x
Pictures of the Best and Worst Foods for Gut Health (webmd.com)
Tea Compounds and the Gut Microbiome: Findings from Trials and Mechanistic Studies – PMC (nih.gov)