The brain-gut axis (BGI) refers to the bidirectional communication between the central nervous system and the enteric also known as intestinal nervous system, which links the emotional and cognitive centres of the brain with peripheral gut functions.
This bidirectional communication network includes the central nervous system (CNS), both the brain and spinal cord, the autonomic nervous system (ANS), the enteric nervous system (ENS) and the hypothalamic-pituitary-adrenal axis.
Recent research has pointed out that the cornerstone of this communication within our bodies is the gut microbiota which influences these interactions. But why is the microbiota important?
Because the interaction between the microbiota and the gut-brain axis appears to be bidirectional, meaning that there is communication from the brain to the microbiota and vice versa via neural, endocrine, immune, and humoral links.
Microbiome, Microbiota, and Meta-genome, who are They?
Although the terms microbiome and microbiota are used interchangeably, it should be specified that the microbiota is the set of living microbes in our whole body and in greater numbers in the intestinal flora, while microbiome refers to the whole universe of microbes in our body and their genes.
The gut microbiota has evolved together with humans until today, living in a symbiotic relationship with us and containing the different populations present in the large intestine including bacteria, protozoa, and viruses.
The meta-genome refers to the genes of the microorganisms present in a specific environment such as the microbiota and the collective functions of these microbial genes.
The microbes in our digestive system affect everything in our bodies, in both physical and mental health to our vulnerability to disease.
The bacteria in the microbiome help digest food, regulate the immune system, protect against other bacteria that attack the body, and produce vitamins including B12, thiamine and riboflavin; as well as vitamin K which is needed for blood clotting.
At the brain level, the autonomic system with its sympathetic and parasympathetic branches directs signals from the gut to the central nervous system (CNS) and from the CNS to the gut. The hypothalamic-pituitary-adrenal (HPA) axis is considered the central axis of stress of any kind and is located in the area of the limbic system of the brain that holds memory and emotional responses. Environmental stress as well as elevated pro-inflammatory cytokines activate this system which, through a process involving the pituitary gland, leads to the release of cortisol from the adrenal glands.
The study from which these findings were published also points out that this complex communication system not only ensures the proper maintenance of gastrointestinal homeostasis, but is likely to have multiple effects on affective, motivational, and higher cognitive functions.
An imbalance in the gut may have effects on anxiety, depressive behaviours, as well as autism.
The most important link between the gut and the brain is the vagus or vagal nerve that controls salivation, heart rate and digestion. Reciprocally, the gut responds to the brain by saying "I am satisfied, I feel good"; or through a calm heart rate, "I am calm".
The messages the vagus nerve receives come from metabolites located in the gut flora and messenger substances from the immune and hormonal cells in the gut.
What Happens When your Body's Microbiome is Out of Balance
We all have microorganisms living inside of us and we only become aware of them when we have a stomach-ache, an infection, or an allergy.
Numerous scientific studies now indicate that our individual microbial universe is interwoven with a spectrum of conditions including acne, allergies, obesity, anxiety, cardiovascular disease, irritable bowel syndrome, autoimmune diseases such as diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, fibromyalgia and even cancer because of microbiome dysfunction.
Microbes that attack the body accumulate over time, changing the genetic activity our body and metabolic processes that eventually result in an abnormal immune response against substances and tissues normally present in the body.
Take the case of dairy intolerance: initially, the person has no allergy or discomfort when consuming dairy, but exaggerated ingestion causes a proliferation of harmful bacteria that, eventually, when the person takes it in through food, stomach inflammation, flatulence, nasal congestion and, in some cases, skin reaction, are not long in coming.
Autoimmune diseases are thought to be inherited, not through DNA, but through the family microbiome (1).
There is strong evidence that the colonic microbiome differs between obese and lean twins. Obese twins have lower bacterial diversity and higher enzyme levels meaning that they are more efficient at ingesting food and harvesting calories. Obesity has also been associated with a weaker diversity of microbes in the colon.
Type 1 diabetes is an autoimmune disease associated with a less diverse gut microbiome. In animal studies, bacteria play a crucial role in the development of diabetes.
Dust in homes with dogs can reduce the immune reaction to allergens. In addition, asthma can also be triggered by changing the composition of the gut microbiome. Further to this, Children living in homes with dogs can develop enhanced immunities and have been found to be less likely to develop childhood allergies.
My Top Strategies to Maintain a Healthy Gut
- If you want to start off on the right foot, it would be good to do a purge or cleanse, or at least practice some form of intermittent fasting.
Note: In this protocol, it would be best to practice some form of fasting every other day for 2-4 weeks to consolidate its benefits and, on the days when you eat normally, avoid junk food, and added sugars.
- Engage in a cycle of probiotics (30-45 days) to help repopulate the gut with good bacteria. This will strengthen you on several levels:
- Digestive because a healthy colon allows you to better absorb the food you eat and the nutrients it contains.
- Strengthens the immune system. 70% of the body's immune cells are found in the gut; the probiotic Bifidobacteria infantis alone has been shown to increase T-cells that help prevent autoimmune diseases and chronic inflammation.
- Mental and emotional. Bacteria in the gut produce neurotransmitters that help promote sleep quality, mood, stress management, anxiety management and cognitive function.
In addition to probiotics in supplements, some foods that contain probiotics are sour cabbage, Kimchi (an oriental preparation of fermented vegetables), miso (fermented soy), Kefir (unsweetened, of course) and Kombucha.
- Add prebiotic foods to your diet, especially on non-fasting days. These are foods that feed the good bacteria already in your gut to strengthen them.
In addition, prebiotics have their own added benefits to encourage you to include them even more in your diet:
- Bacteria in the colon begin to feed on the fibres of prebiotics and can produce short-chain fatty acids. These include butyric acid, which balances and regulates electrolyte levels in the body, while increasing the resistance of the intestinal lining.
- Prebiotics are involved in hormonal health by acting as an adaptogenic compound that regulates the release of cortisol (stress hormone).
- Prebiotics may help increase bone density by facilitating the production and bioavailability of various vitamins and minerals such as calcium, iron, and magnesium.
Top Prebiotic Foods
Caution: prebiotics may cause bloating and gas in some people, so start with small amounts and cooked as they seem to be harder to tolerate when eaten raw.
Foods rich in prebiotics:
Artichokes, Nori seaweed, cruciferous vegetables such as kale, broccoli, cauliflower; berries, asparagus, red onion, leeks, apples, Konjac root or glucomannan, jicama; cocoa powder, flaxseed, radish, coconut,coconut flour; sweet potatoes, hemp seeds and cabbage.