It may seem an unlikely link, but research published over the last few years increasingly points to a diet rich in high-fibre foods playing a role in a reduction in the symptoms of stress, anxiety and low mood.
The second brain
Have you ever heard the gut being referred to as the ‘second brain’?
Scientists now know that the enteric nervous system (ENS) located in our gut does far more than just digest our food. The ENS is capable of communicating with your central nervous system (CNS), which is comprised of your brain (that is, your actual brain!) and spinal cord.
The ‘second brain’ label refers to a complex system of neurons that line our digestive system. These neurons send chemical messages directly to the brain via the brain stem and receive messages in response.
So, simply put, the gut and the brain ‘talk’ to each other in a way that does not happen with other organs of the body.
The mental health connection
So, what does this have to do with mental health?
Well, your microbiome (the trillions of microbes and bacteria that live in your gut) thrives on a healthy balance of ‘good’ and ‘bad’ bacteria. Your microbiome knows whether your gut is in balance and communicates this information straight up to your brain via the vagus nerve.
Scientists in Belgium published a study in 2014 which found that having the right balance of microbes in their microbiome correlated with a person’s quality of life and whether they experienced depression.
95% of your body’s serotonin also lives in your gut. Serotonin – known as the ‘happy hormone’- is a neurotransmitter which sends chemical messages from cell to cell in your body. Normal levels of serotonin are associated with mood balance whereas low levels are linked with depression.
Your gut is continually sending signals to your brain, this means if there’s an imbalance of microbes or hormones, your gut will broadcast directly to your brain where it will manifest in low mood, anxiety or stress.
And where does fibre come in?
Fibre keeps your gut clear by encouraging regular bowel movements.
This rids your body of waste products including undigested food, minimising imbalances in gut flora caused by having unwanted microbes hanging around. The ENS (your gut) will then ‘speak’ to the CNS (your brain) with the message that all is well. As a result, this will reduce your chances of feeling stress, low mood and anxiety.
Further, a type of soluble fibre called resistant starch could hold the key to better mental wellness.
Resistant starch, found in green bananas, beans and lentils, ferments in the large intestine feeding the gut with ‘good’ bacteria and producing short-chain fatty acids which are beneficial to health.
A study at Oxford University published in 2014 found that giving volunteers doses of the resistant starch led to lower levels of ‘stress hormone’ cortisol and a lower stress response during tasks during than volunteers who had been given a placebo.
So, should I be eating more fibre to boost my mental health?
The short answer is most likely, yes.
How much fibre per day?
According to UK government guidelines, adults should be getting 30g fibre a day. Around 9 in 10 people in the UK are not meeting this with most adults eating an average of 18g a day.
It is a good idea to eat a mixture of soluble fibre, found in oats, peas, beans, citrus fruits, carrots, barley and nuts, insoluble fibre, found in wheat bran, brown rice, cauliflower, potatoes, tomatoes, cucumbers, carrots and nuts, and resistant starch.
Last updated: 23 March 2020
Sources
https://link.springer.com/article/10.1007%2Fs00213-014-3810-0
https://www.nature.com/articles/s41564-018-0337-x
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4662178/
https://www.nhs.uk/live-well/eat-well/how-to-get-more-fibre-into-your-diet/
https://www.ncbi.nlm.nih.gov/pubmed/30292888
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6469458/
