Your gut and your brain are intricately linked by the vagus nerve, this is what is commonly known as the gut-brain axis. This a super two way motorway between your brain and your gut that can have a significant impact on our mood, sleep and mental health.
Serotonin - our “happy hormone”
A neurotransmitter known as serotonin is found at both ends of the vagus nerve. It an important regulator of mood and is also know as our happy chemical (often labelled the “happy hormone” even though it is not strictly a hormone). Low levels of serotonin can be linked with depression, anxiety and insomnia.
Serotonin is also a precursor to melatonin, of which when our body has adequate levels, we are able to sleep and regulated our body clocks better. This is one explanation for why when we are feeling low in mood or anxious we can have disturbed or altered sleep.
Serotonin is hence crucial to the functioning of our brains as well as our mood. However, over 90% of serotonin production in our body takes place in the gut.
While we think that the serotonin produced in the gut cannot enter the brain (unable to cross blood-brain barrier) what we do know is that it can send messages up to the brain by the vagus nerve which has been shown to have a significant impact on our mood and mental health.
Tryptophan - precursor to serotonin
Serotonin is a protein which, like all proteins, is made from chains of amino-acids. One of these amino acids called tryptophan contributes directly to the production of serotonin. Tryptophan cannot be produced by the body and hence has to be consumed in our diets. The amount of serotonin produced in the brain is dependant directly on how much tryptophan is present in our diets. This conversion of tryptophan, that we eat, to serotonin in our body and brain is a result of your gut microbiome having enough well fed good bacteria to allow this process to take place.
So where do we get tryptophan from, I hear you ask
The is no guidance in the UK on the amount of tryptophan we should be consuming in our diets but in the USA the recommended daily amount (RDA) for adults is 5mg/kg body weight per day.
Complete proteins such as meat and fish are high in tryptophan but other non-meat sources include nuts, eggs, soybeans and tofu. There are plenty of whole food plant based sources of tryptophan such as legumes, grains, nuts and seeds which have then added benefits of being unprocessed and high in fibre which our gut microbiome loves!
While of course we are not suggesting that severe depression, anxiety of suicidal thoughts can be overcome entirely by just eating the right foods, what we do feel is that as move away from the “a pill for every ill” mantra we have to look holistically at our lifestyles and what factors are potentially contributing to how we are feeling, all in keeping with the latest scientific data we have at our disposal.
The treatment of mental health problems simply cannot be standardised to a one size fits all approach. Encompassing physical activity, dietary changes and mindfulness practices can all have a significant impact on our mental health just as medications like SSRIs can too. It really is about finding the right balance for the individual.
Updated 28th April 2020