Nutrition and the gut brain axis

The gut brain axis is the name given to the two-way communication between our brain and gut. Unsurprisingly it’s likely to be really important in relation to our mental health. Consequently the gut or more specifically our gut microbiota (the trillions of bugs living in our gut), is often referred to as the ‘second brain.’ So for mental health awareness month I thought I’d take a look at nutrition and the gut brain axis.

Physically several nerves connect the brain and the gut. The large, complex Vagus nerve is particularly important. There is preliminary evidence for a beneficial effect of a healthy, diverse gut microbiota on mood and anxiety. These benefits seem to be partly mediated by the impact of the microbiota on the activity of the Vagus nerve. 

Chemically the brain and gut are linked through:

  • Neurotransmitters,
  • Hormones,
  • Bile acids,
  • Pro-inflammatory chemicals and
  • Short chain fatty acids. 

Some of these chemicals are produced by our gut cells and others by our gut microbiota.

We know that the health of our gut microbiota is influenced by diet, probiotics (live bacteria and yeasts) and prebiotics (carbohydrates that feed our beneficial bacteria.)

Probiotics are a compelling topic for mental health research. This is because it would be relatively easy and inexpensive to use them as a preventative strategy or as treatment. You can read more about them here
.There are obvious advantages to this but wider dietary changes would likely have numerous additional health benefits. Consequently I am keen to see both areas researched equally. It’s also important that research into probiotics is designed to give information about specific strains, doses and optimal treatment durations. A present this data is lacking. 

For example research has shown that probiotics may relieve depression and improve sleep quality and duration by increasing serotonin and anti-inflammatory chemicals produced by our gut microbiota. However we don’t yet know the ideal duration of treatment, dosage, or the strains of probiotic that would be most useful. We also know that dietary tryptophan is needed for the production of serotonin. This means that there may also be a role for dietary sources of tryptophan. Milk, oily fish such as salmon, poultry, eggs, cheese and for vegans soya products are useful sources. You can read more about diet and sleep here
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The gut microbiota also produces the neurotransmitter gamma-aminobutyric acid (GABA), which reduces neural activity in the brain and helps control fear and anxiety. Several studies suggest that increased GABA levels in the human gut could be due to bacteria such as Bifidobacteria and Lactobacilli. Research is ongoing looking at the impact of specific strains.

Conversely some bacteria in the gut produce inflammatory chemicals, which can increase our risk of depression, dementia and schizophrenia. We also know that differences in the gut microbiota are associated with some of the challenges faced by autistic people. 

Overall Lactobacillus and Bifidobacterium strains (specifically the L. helveticus and B. longum) show the most promise at the moment. Researchers are even calling these strains “psychobiotics” for their potential therapeutic benefits in mental health. Remember that these strains have been more heavily researched than others. New information may lead to interest in other micro-organisms.

In relation to prebiotics there is some research that suggests that taking the prebiotic galacto-oligosaccharide (GOS) for 3 weeks can significantly reduce the amount of the stress hormone, cortisol circulating in the body. Again it’s early days and the research evidence is a long way from being able to show cause and effect. Furthermore we cannot give clear guidance about the amounts required. It’s also really important to be aware that GOS can significantly exacerbate gastrointestinal symptoms for some people with Irritable Bowel Syndrome.

In terms of everyday food there is growing evidence for the benefits of eating a broadly Mediterranean style diet as a means of improving our mental health. The strongest evidence at the moment relates to depression and dementia. Again we need more research. However as this way of eating is also beneficial for cardiovascular health I recommend: 

  • Eating plenty of fish, especially oily fish
  • Using olive oil for cooking
  • Making sure you have a wide range of different plant foods with plenty of fruits, vegetables, wholegrains, nuts and seeds. 
  • Eating less highly processed food
  • Cutting back fatty/sugary snacks and drinks 

Fermented foods such as kefir, kombucha. miso, kimchi and sauerkraut may also be useful. However these foods tend to be very high in salt and sugar, which have a negative impact on our health. If you enjoy them and find them beneficial include them in moderation to avoid the potential downsides. 

For those of you who are interested in finding out more about brain boosting foods download my free meal plan here
. If you know a tween or teen who would like to boost their brain health click here
to grab my e-guide “Brain food for tweens and teens.” You can also schedule a call if you need individual support or help with a school or youth group project. Finally the NHS has some fantastic resources to help us all achieve and maintain great mental health so check out what’s available here
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