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The Gut-Brain Axis

The gut-brain axis teaches us that our mental health and our physical wellbeing are inextricably linked. We can influence our mood by what we choose to eat and our lifestyle choices, and conversely, the state of our emotional health influences our digestive and physical health.

How Does the Gut-Brain Axis Work?

The gut-brain axis is a bidirectional complex network of communication between the gut and brain and includes:

  • The central nervous system – spinal cord and brain.
  • The enteric nervous system – a complex web of neurons surrounding the gut.
  • The sympathetic and parasympathetic nervous system – fight/flight & rest/digest.
  • The vagus nerve.
  • The HPA axis – endocrine/hormone pathways.
  • Immune system – the majority of our immune cells are in the gut.
  • Gut microbiome – the community of microorganisms living in our gut.

If we just focus on two aspects of the gut-brain axis here….

1. The Gut Microbiome

The bacteria in the gut outnumbers the body’s cells 10-1 – we are only 10% human!

A healthy gut microbiome is dependent on dietary diversity. A loss of species diversity is common in several disease states such as diabetes, asthma, obesity and IBD. The broader your diet is, the more diverse your gut bacteria will be: the healthier your microbiota will be, the healthier you will be!

Specific bacteria have the capacity to affect the brain both negatively and positively e.g.

  • The presence of Campylobacter jejuni bacteria can increase anxiety levels.
  • Meanwhile, key commensal bacteria such as Lactobacillus and Bifidobacterium can send calming, safety signals back to the brain.

2. The Vagus Nerve

The vagus nerve is connected to the parasympathetic nervous system, the ‘rest and digest’ arm of the autonomic system. It is the longest cranial nerve in the body, originating in the brain stem, branching out, connecting to major organs along its way to the colon. The vagus nerve oversees a wide range of vital bodily functions.

It senses the microbiota and the state of the organs and sends this Information from the gut, liver, heart, and lungs to the brain. This allows the central nervous system in the brain to constantly survey what is happening around the body and adjust our physical response accordingly. You can read more about the vagus nerve in my blog.

How can we Support the Gut-Brain Axis?

Bottom Up: Influencing microbial diversity

  1. A high fibre rich diet including a wide diversity of whole grains, vegetables fruits, nuts, seeds and legumes.
  2. Prebiotics to feed the beneficial gut bacteria:
    • Resistant starch:
      • Oats, barley, beans and legumes
      • Cooked and cooled rice, pasta, potatoes and sweet potatoes
      • Green bananas
    • Other great sources of prebiotics include:
      • Jerusalem artichokes
      • Onions, leeks and garlic
      • Asparagus
      • Bananas, pears and watermelon
  3. Probiotics: Beneficial microorganisms that boost your microbiome diversity:
    • Raw sauerkraut
    • Kimchi
    • Kombucha
    • Miso
    • Pickles
    • Yoghurt
  4. Polyphenols are bioactive compounds that increase beneficial bacteria and decrease certain harmful bacteria. Highest levels are found in:
    • Fruits: blueberries, blackcurrants and blackberries, raspberries, strawberries
    • Vegetables: artichokes, red onion, shallots, spinach
    • Flaxseeds
    • Herbs & spices: cloves, peppermint, star anise, oregano, sage, rosemary and thyme
    • Coffee and tea
    • Cocoa
  5. Microbiome testing can be very helpful as part of the consultation process and it allows me to personalise dietary and supplemental advice based on an understanding of your particular bacterial patterns.

Top Down: Stress reduction

  1. By calming the mind we are nurturing the gut, the gut barrier and reducing inflammation in the body:
    • Take up Yoga, Tai Chi or Qi Gong
    • Adopt a regular meditation practic
    • Learn how to use breathing practices to manage stress level
    • Prioritise 7-8 quality hours sleep every night • Connect with nature
    • Consider herbs and nutrients that soothe the nervous system. Always do this under the guidance of a professional.
  2. Supporting the vagus nerve: Stimulation of the vagus nerve in times of stress, sends a message to our body to relax. Long term benefits can follow in relation to mood, pain management, overall wellbeing and resilience.
    • Slow, deep belly breathing triggers the vagus nerve to slow heart rate and reduce blood pressure. If we take 3 breaths before eating, the parasympathetic nervous system is activated via the vagus nerve and we switch in to rest and digest.
    • Singing, chanting and gargling activate the vocal-chords which then stimulates the vagus nerve
    • Cold water immersion has been scientifically shown to support mental wellbeing, stimulate the gut, decrease heart rate and boost the immune system, in part by activating the vagus nerve. Take a dip in your local outdoor pool or the sea on a regular basis. Or turn the water to cold for at least 30 seconds at the end of your shower and immerse your forehead eyes and at least 2/3 of both cheeks into cold water. Reflexology can assist in stimulation of the vagus nerve to lower heart rate and blood pressure.
    • Laughter may really be the best medicine! The diaphragmatic breathing and vagus nerve response triggering relaxation.
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