How Food Affects Your Mood

Understanding the gut and brain connection

The father of modern medicine and Ancient Greek physician Hippocrates stated that ‘all disease begins in the gut’.

Now more than 2000 years later this idea has captivated the attention of many. You may hear the gut being referred to as the ‘second brain’ and we often hear idioms such as ‘gut feelings’ and ‘trust your gut instinct’ when we are dealing with situations that trigger our nervous systems. As it turns out, this connection between the gut and brain is not just a metaphor. When you’re stressed, anxious or nervous your gut knows it instantly. 

In this article we’ll discuss how your food affects your mood.

The Gut Microbiome

There is said to be trillions of microbes that exist in the body. Most of these are in our intestines, more specifically residing in our large intestine, and on our skin.

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The gut microbiome also referred to as the gut microbiota is a complex system of bacteria, viruses, fungi and genetic material that colonise the gastrointestinal tract. This tract starts at the mouth (where food enters) and extends to the anus (where indigestible waste leaves).  

In certain circles of discussions about microbiomes, there can be a tendency to refer to them as ‘good’ or ‘bad’ bacteria. But this is actually a little too simplistic. The best way of thinking about your gut microbiome is to imagine a rainforest.

“Microbiome is a term that describes the genome of all the microorganisms, symbiotic and pathogenic, living in and on all vertebrates. The gut microbiome is comprised of the collective genome of microbes inhabiting the gut including bacteria, archaea, viruses, and fungi.”

Science Direct

Rainforests have layers to them. At the top you have a canopy of big long trees and a diverse ecosystem. Below this top layer lies the smaller shrubs and leaf litter. Beneath that is the forest floor, covered in moss. 

If something happened to the top layer, the rainforest’s canopy, and it was removed, what would happen to the ecosystem? Different trees would then grow, the shrubbery and moss below would probably dry up, and the various diverse species may move on or die. 

There are also layers in the gut. Just as the organisms in that rainforest would struggle to survive in the drastically changed environment, so too the microbes relying on the mucus layer will struggle to thrive in a gut where mucus is depleted or sparse.

There is still much we don’t know and are still learning about gut microbiomes and its various functions in the body. But we do have a fair idea how it’s formed and how it can be altered.

Everyone has their own unique and individual biome. Largely formed during the first few years of life, factors influencing its composition include how you were born (vaginal birth versus C-section), infant feeding (breastfeeding versus bottle feeding) and exposure to antibiotics. During the following years of our lives, our gut microbiome keeps relatively stable, although it can be altered throughout the lifespan by factors such as diet, stress, sleep and exercise.

The Gut-Brain Axis

The communication network between your gut and brain is called the gut-brain axis. The gut and brain have a two-way connection that operates physically and biochemically via the Vagus nerve and nervous system. 

An important aspect in the gut-brain story is that 90% of serotonin receptors are located in the gut. Serotonin is a neurotransmitter that has many important functions in the body. It is often referred to as the happy hormone because it contributes to wellbeing and happiness by playing a role in appetite, mood and sleep. Serotonin is likely just one of many other biochemicals impacting our mood and behaviour.

What foods best support a healthy gut microbiome?

The food we consume can significantly impact our gut microbiota as we know that greater microbial diversity is associated with better health outcomes. Some of the world’s best diets linked to longevity are all high in plant-based foods, and the traditional Mediterranean diet gets top marks! Here’s why.

The Mediterranean diet offers a huge diversity of:

  • Vegetables
  • Salads
  • Legumes (beans and pulses)
  • Fruit
  • Wholegrains
  • Nuts
  • Seeds 

It also contains high amounts of omega-3 fats (found in oily fish), extra virgin olive oil and tends to offer fermented dairy (Greek yoghurt and cheese in small amounts), wine (in low to moderate amounts with meals), and minimal red meat. In contrast, the Western diet is typically highly refined and processed therefore linked to less gut microbial diversity.

Diversity is key for increasing your gut microbial diversity so aim for 30+ different plant-based foods per week. 

Go for a variety filling up on fibre-rich whole plant foods. Many of these foods contain prebiotic fibres that feed you friendly gut bacteria. 

Experiment with fermented foods like kefir, kimchi and sauerkraut. These traditional foods have been around a very long time and they contain live bacteria, are cost effective and easy to make at home.

Polyphenols-rich foods all contain plant chemicals that have a prebiotic-like effect that also positively impact our mood. Food types that are rich in polyphenols include:

  • Cocoa
  • Turmeric
  • Oranges
  • Berries
  • Spices
  • Dried herbs
  • Seeds
  • Nuts
  • Olives
  • Cinnamon
  • Extra virgin olive oil
  • Green tea

The Seven Principles of Eat Yourself Healthy

Dr Megan Rossi, aka the gut health doctor, summarises seven principles in her book Eat Yourself Healthy:

  1. Mostly plants
  2. Diversity all the way
  3. Whole and natural versus refined and perfect
  4. Herb and spice your life
  5. Get among legumes
  6. Dabble in fermented food
  7. Taste, explore, chew and enjoy

Environmental Factors

Remember there are also other factors in our environment that impact our gut microbiome throughout our lifespan. 

Here are some examples to consider:

  • Stress and conflict
  • Antibiotics
  • Medications
  • Poor sleep
  • Smoking
  • Disease
  • Exercise
  • Meditation
  • Breastfeeding
  • Pets
  • Gardening
  • Nature (ecotherapy)


Understanding the gut and brain connection is an ongoing and endlessly fascinating area of research. What is clear is that there is a very close connection between the two and that food certainly can and does affect your mood. As it turns out, to a certain extent you are indeed what you eat. Why don’t you take a moment to consider what you eat and how you live your life? Are you allowing the ‘creatures’ in your gut to survive and thrive?

If you’d like support, motivation or inspiration about healthy eating and living, or maybe you just want to know how on Earth you can achieve including 30 different types of plant-based food in your diet, give us a call and book a friendly, non-judgemental appointment with us!

– Diana D’Auria, Dietitian

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