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  • Writer's pictureTom Robinson

The microbiota-gut-brain axis: the relationship between nutrition and mental health explained

Updated: Jan 28, 2022

Yesterday, I introduced the gut-brain axis and started to explain the importance of nutrition and its relationship, and influence on our mental health.

Today, I am adding the thoughts and expertise of two highly qualified experts in this field who explain this relationship in more detail and also give us some suggestions for how we can start to modify our diets.

The following is an extract from an article by Registered Nutritional Therapist Venetia Mitchell written in collaboration with Professor David Veale.

I have highlighted the text that I find particularly useful and added a link to the full article at the bottom of the page.

I hope you all find this as enlightening and fascinating as I do!

What we know

The ecosystem of bugs in your gut is called the gut microbiota (or gut microbiome) and its relationship with our brain is known as the ‘gut-brain axis’.

We are born with our own unique ecosystem of microbes that exist symbiotically with our bodies.

How this ecosystem is made up is initially influenced by our mother’s microbiota. There is also some evidence to suggest that the way we are born (caesarean vs vaginal birth) can affect our microbiome.

As we age, we develop individual microbiome ecosystems. These can be influenced by a range of genetic and lifestyle factors. For example, eating lots of processed or junk food which are high in fat and sugar, lack of physical activity, smoking or antibiotics do not help the gut microbiota.

“Our gut’s ecosystem has been shown to impact the levels of chemicals influencing the brain. This influences our mood. At the same time mental stress and low mood has been shown to negatively impact the balance of our gut microbiota.”

Evidence from a range of sources is emerging to suggest that people with different mental disorders like depression or anorexia have distinct gut microbiota compositions.

For example, studies that transplanted human gut microbiota from depressed patients into germ-free mice repeatedly find the mice become withdrawn and inactive. Researchers also see changes in the biochemistry of the mice brains.

What might a depressed human’s microbiome look like?

An imbalanced (dysbiotic) gut microbiome has been associated with depression. A depressed person is likely to have a low level of ‘beneficial’ species of bacteria and overall lack of diversity.

The functionality of a patient’s gut microbiome can be tested by means of a Microbiome Test.

Dietary Recommendations

Scientists suggest that the optimal route towards gaining a healthy gut microbiome, and therefore a healthy gut-brain axis, is to consume a wide range of colourful, whole, plant-based foods: i.e. real foods including fresh vegetables, pulses and legumes.

To help understand why, it is helpful to learn about ‘prebiotics’ and ‘probiotic’ foods.


A healthy gut microbiome is made up of different live bacteria that provide benefits to our health and work with us in symbiosis.

For example, many of them feed off the fibrous foods we eat and create the Short Chain Fatty Acids that improve our mood. These beneficial species are called probiotics.

Common probiotic microbes are members of the families, Lactobacillus and Bifidobacterium. You can read more here.

Examples of these probiotic foods are fermented foods such as sauerkraut, natural live yoghurts, kimchi, kefir, kombucha, miso soup, tempeh, sour pickles, fermented soft cheeses as well as commercial milks like Biomel.

Probiotic foods introduce beneficial bacteria to help to enrich the diversity of our microbiota: but don’t stick to the same ones all the time as diversity is important. A review by Wallace (2017) found that daily intake of probiotics reduces depression and anxiety.”


Prebiotics are foods that nourish the beneficial gut microbes. Gut bacteria feed off prebiotic foods and transform them into beneficial substances for the body, for example Short Chain Fatty Acids.

These may influence our gut-brain axis, improving our mood. Colourful, whole, plant-based foods tend to be prebiotic and contain a lot of fibre.

Dietary fibre comes from a range of plant-based carbohydrates that are not digested in our small intestine but reach the large intestine or colon where they are then broken down and utilised by our gut microbes. Because of this, fibre is an example of a prebiotic.

Foods especially high in fibre include Jerusalem and globe artichokes, chicory root, asparagus, lentils, beans, onions, garlic, leeks, bananas, beetroot, broccoli, fennel root, wholegrain oats and barley.

“The key to promoting and maintaining a healthy gut is ensuring diversity in your diet. It may seem overwhelming, yet research suggests we should aim for 50 different vegetables, legumes, grains, nuts, fruits and herbs per week.

To start, it may be more realistic to aim for at least 30 per week and here are some quick tips on how to achieve this easily:

When food shopping, seek to choose fresh herbs and vegetables you may not normally consume. Eating seasonally is a great way to do this easily. Wash vegetables but avoid peeling unless it is really necessary.

  • Add an extra main vegetable to your plate. If you usually have two, try having three.

  • Enjoy the addition of herbs and spices to your dishes. A good simple set of cookbooks that I may recommend are by Rukmini Iyers, such as “The Green Roasting Tin”. They are simple one dish recipes which are easy to put together.

  • Bulk buy nuts and seeds and, if possible, place them in containers on your kitchen side in order to sprinkle them on both savoury and sweet dishes throughout the day.

  • Uncooked/ raw foods are better for higher fibre. If you are not used to consuming these foods, to avoid gut discomfort, it is recommended you start slowly and work on building up intake. It can also help some people to incorporate prebiotic supplements like Bimuno. Gut testing can help determine what fibre you might be missing.


Polyphenols are natural chemicals found in many foods. They are designed to protect the plant and are also responsible for the bright and vibrant colours of fruits and vegetables.

When we consume these colourful plants (often referred to as ‘eating the rainbow’) we gain antioxidant and anti-inflammatory benefits that help prevent illness and disease.

Our gut microbiota love these polyphenols too. Bugs in our gut transform polyphenols into bioactive substances. Polyphenols also promote the growth of beneficial gut bugs and as a result, they are considered prebiotics.

An example of a food rich in polyphenols is dark chocolate with a cocoa content of 85% or above. Eat a square or two a day! A recommended supplier is Cocoa Runners. Other foods rich in polyphenols are green and black tea and berries.

“Mental health benefits from consumption of such prebiotic polyphenols include reductions in stress, depression and possibly reducing the risk of Alzheimer’s. As is so often the case, more research is needed, but in a controlled study of older adults by Bowtell (2017), just a quarter cup of concentrated blueberry juice a day improved cognitive function after 3 months.

Sourdough bread

In addition to consuming colourful, plant-based foods, a great way to gain both prebiotic fibre and polyphenols is to focus on good quality grains, such as a whole grain Sourdough bread.

Sourdough is baked using a natural yeast (also called “starter” or “leaven”) simply made from wholegrain flour, bread, and salt.

The process allows for a natural fermentation of the fibrous wholegrain. A long, slow fermentation of the dough lowers the amount of gluten and through the production of lactic acid bacteria, creates the ideal environment to promote the absorption of the nutrients from the wholegrain.

"All wholegrains contain gluten, and which in some people causes damage to the gut wall, promoting inflammation."

Sourdough bread is a great way to lower any negative effects. A standard, refined, industrially made bread may cause, and at the same time, boost, your intake of quality prebiotics.

“Ideally however, home baking is recommended to guarantee a long fermentation (how long you leave your dough to sit).”

If you are new to baking and the concept of sourdough bread, we recommend The Sourdough School. You can join their Sourdough Club to understand, learn, and find out more about why sourdough may boost your mood.

Online tuition, deeper understanding and a supply of recipes are provided, and you can access their website here.

* *

A huge thank you to Venetia and David for taking the time to write such an informative article. If you would like to read the full text or are interested in further research in this area, then you can find links to information and further reading here.

Thank you so much to Venetia for reaching out to me through the blog and for alerting me to all of this vital information!

Anyone who would like to know more about Venetia’s work can contact her for a consultation through her website, a link to which I have added here.

I will most definitely be returning to the subject of nutrition and the gut-brain axis in my future posts, but the first thing I am going to do is to start making Sourdough Bread!

I think the whole process is going to be beneficial; from the mindful act of kneading and baking, and the positive effects of nurturing the Sourdough Starter, to reaping the physiological benefits in the eating and digesting! – This is going to be an enlightening and very interesting experience!

My Sourdough Starter is currently waiting for me in the kitchen (having created it last night), and I am now going to see if there are any signs of action!

I really think this process could prove (couldn’t resist sorry!) hugely beneficial!

Thanks for reading,

Speak to you soon,


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