The Microbiome and Gut-Brain Axis

Did you know we are actually more non-human than human?! We carry up to 2 kg of microbes and have around 100 trillion of these microorganisms on or inside us. They outnumber our human cells by at least 10 to 1.

Did you know these microbes could be influencing your health?

Accumulating evidence demonstrates that a disturbed microbiota is not only linked with gut health disorders, but can potentially influence conditions like depression, obesity, epilepsy and more.

What is the human microbiome?

Trillions of organisms including bacteria, viruses, funguses and microscopic animals call our body home. They live on our skin, in our mouth and even inside us. But before you run off to have a long shower and begin scrubbing frantically to get rid of them, it’s important to understand that this is normal, and like other mammals we rely on these organisms for our health, happiness and wellbeing.

These organisms make up our microbiota. 95% of our microbiota is found in our gastrointestinal tract – our gut. The combination of these microbes, their genes, the environment they live in and the stuff they produce is called out human microbiome. The microorganisms specifically found in our gut is called the gut microbiota, formally known as Gut Flora.

We have known of this symbiotic relationship with microscopic organisms for a long time, but its only relatively recently that we have been researching into how these organisms effect our overall health. It’s interesting to note though that for over 5,000 years’ traditional medicines, including Ayurveda, have always considered the health of the digestive system to be the key to wellness. First line of treatment in these traditions involves strengthening the digestive system to heal a wide range of conditions. Science is now showing how this occurs on a deeper level.

Research has shown that the health of the microbiome is linked to a wide range of health conditions such as obesity, asthma, allergies, autoimmune conditions and diabetes. It also influences how our brain functions and is linked to depression, anxiety and stress.

Why do we have gut bacteria?

Colonization of the gut bacteria and microbiota is an inevitable consequence of living as a mammal.

The composition of each induvial gut microbiota is unique and is constantly changing due to what we eat, where we live, who/ what we live with, what we touch, the air we breathe, environmental factors and even how we were born.

Microbes begin to occupy us the moment we are born. An infant’s gut microbiota is also influenced by breastfeeding. For example, Gut Microbiota Worldwatch claims that breastfed babies have Bifidobacteria - considered a friendly bacterium which benefits the gut - whilst babies reliant on formula are likely to have less of these bacteria.

We share a symbiotic relationship with our microbiota. Having microorganisms is beneficial for us and the more diverse our microbiota, the better.

A Canadian study found that infants with less diverse gut microbiota at 3 months were more likely to have food sensitivities to eggs, milk and peanuts by 12 months (Azad, et al, BJOG, 2015.)

Much of the microbiota live with us in a symbiotic relationship that is mutually beneficial. However, there are also opportunistic pathogens that can invade us and cause disease or other health problems.

Benefits of the microbiome:

• It keeps our gut strong and healthy as it aids in the release and function of our digestive acids and enzymes
• It boosts immunity by supporting mature development and functionality of the immune system. It strengthens our first line of defence against pathogens or bacteria or viruses which can cause disease by providing competition for nutrition in the gut.
• It helps absorb nutrients by metabolising indigestible food compounds. It also helps produce essential vitamins and other nutrients – such as B vitamins, Vitamin K.

An exciting new area of research emerging is the quality, quantity, and composition of the bacteria in your gut have enormous influence on your brain.

How the microbiome can impact our health & brain

A growing body of research is mounting showing that microbes in the gut can influence behaviour and alter brain physiology and neurochemistry. Although the science is still in its infancy, there are some interesting findings. We know that over 25 different diseases are associated with changes in the composition of the gut microbiota. These include inflammatory bowel disease (IBD), allergy, diabetes, IBS and obesity.

Research is also showing that the health of our gut microbiome is linked to nervous system conditions such as anxiety, Alzheimer’s, depression, learning and behavioural issues, Autism, Parkinson’s and much more.

How does the gut affect the brain?

The brain and the gut are intimately connected. We have all felt this connection. Think back to the last time you were nervous. You had the feelings of ‘butterflies’ in your stomach. Or when you saw something repulsive you may have felt nauseas?

That sensation in your gut is coming from a network of neurons which line our intestinal walls. This mass of neural tissue is so extensive that some scientists have nicknamed it the “second brain”. This is called our enteric nervous system and contains around 100 million neurons – more than what is found in the spinal cord!

From this we can gather that whatever is happening in one, also effects the other. This is called the gut-brain axis - the connection of our microbiome to the health of the brain.

Can the microbiome affect stress, anxiety and depression?

Emeran Mayer, Professor of Physiology, Psychiatry and Biobehavioral Sciences at the David Geffen School of Medicine at the University of California, Los Angeles (U.C.L.A.) suggests that “a big part of our emotions are probably influenced by the nerves in our gut”.

According to the American Psychological Association (APA), gut bacteria produce an array of neurochemicals that the brain uses for the regulation of physiological and mental processes, including memory, learning and mood. In fact, 95% of the body's supply of serotonin (our happy brain chemical) is produced by gut bacteria, according to the APA. Therefore, supporting this production can help overcome these nervous system conditions.

Animal tests have shown that probiotics (supplementing with ‘good’ bacteria) can reduce anxiety-like behaviour in mice. In another study a probiotic was compared to an antidepressant under stressful situations. Both the probiotic and drug were effective at increasing perseverance and reducing levels of hormones linked to stress (Desbonnet et al, 2010.)

How to support the health of our Microbiome

Since most of our microbes live in our colon and small intestines, what we eat feeds our microbiota. What its needs to flourish is high fibre, complex carbohydrates.

In 2014 a study published in the journal Psychopharmacology found that prebiotics - carbohydrates that boost healthy bacteria in the gut - may be effective for reducing stress and anxiety.

What we eat or take can also weaken our microbiome. Pharmaceuticals such as anti-biotics, the oral contraceptive pill, antidepressants all wipe out our beneficial bacteria. Foods such as coffee, alcohol, refined sugar, Artificial and GMO Foods also disrupt the balance.

They key areas are:

1. Eat a Diverse Range of Foods.
2. Eat Lots of Vegetables, Legumes, Beans and Fruit.
3. Eat Fermented Foods.
4. Don't Eat Too Many Artificial Sweeteners.
5. Eat Prebiotic Foods.
6. Breastfeed for at Least Six Months and vaginal birth.
7. Eat Whole Grains.
8. Eat a Plant-Based Diet.

Foods that support Gut Health

• Pre-biotics:
  • These act as a food source for our friendly bacteria. This includes high soluble fibre foods such as oats, barley, apples, leafy greens, sweet potato, onions, leek and herbs such as slippery elm, licorice root, marshmallow root
• Fermented foods:
  • These provide a good dose of friendly bacteria. Please note that fermented foods are traditionally used as a condiment – so take small amount with meals. They are very heating to the body so best consumed in the cooler months. These include kimchi, sauerkraut, yoghurt, kefir, kombucha, tempeh, pickles, Natto.
• Ghee:
  • A natural source of butyric acid which the cells in the gut use to energy and their and supporting the health and integrity of the intestinal wall
• Seasonal vegetables:
  • The mix of bacteria that live in our gut changes throughout the year, to match the food we eat in every specific season.

Supplementing with a good quality pro-biotic is also a great way to support the microbiome. Please talk to your health practitioner to recommend one specific for your health state and aims. 

Written by Tegan Wallis

Naturopath, Ayurvedic consultant and Yoga teacher

If you would like to make an appointment with Tegan please visit here for more info.