“We are what we eat” is a well-known phrase, as is “Food be thy medicine, medicine be thy food,” yet there is still a lot of disbelief (or misunderstanding) of how important our diet is for our health.
This is partly because we live in a world of quick fixes, pharmaceuticals are readily prescribed when often lifestyle changes are a more important consideration – although much harder for a doctor to communicate in a 15 minute consultation.
This week we thought we would do a dive into the “gut-brain axis” - the relationship between our digestive system (sometimes called our second brain) and our brain.
Let’s look at the physical first.
Communication between our gut and our brain goes two ways: from the central nervous system, in the brain, to the enteric nervous system in the digestive system (and vice versa). This communication happens through millions of nerves, the largest of which is the vagus nerve. The signaling stimulates a number of internal organ functions, including:
- Cardiovascular activity;
- Reflex actions, such as coughing, sneezing, swallowing and vomiting.
The gut itself is lined with over 100 million nerve cells able to release hormones into the bloodstream that tell the brain messages like – how hungry you are. These hormone signals are slow (which is why many appetite suppressants which act on hormone signaling are not very effective) in comparison to neurotransmitters which are signals produced by the microbe species present in our gut (read more here).
In our gut we host as many as 40 trillion microbes, in fact, more than half our body is not human! The microbes we host have evolved to be able to thrive in our bodies – they are dependent on us and we are just as dependent on them for good health and survival (read more here). An example of a fast acting neurotransmitter is glutamate, which is involved in smell and taste - the vagal neurons pick up a glutamate signal within 1000 milliseconds – faster than the blink of an eye. There are obvious advantages in this speedy transmission, for example, in sensing food which might be toxic to us.
Gut and our emotions
Neurotransmitters contribute to our feelings and emotions. As an example, serotonin is a neurotransmitter often produced in the gut that helps us feel calm and happy. Serotonin also supports our circadian rhythm (read more here).
Another example of a microbe-produced neurotransmitter is gamma-aminobutyric acid (GABA). GABA slows down your brain by blocking specific signals in your central nervous system. GABA is known for producing a calming effect. It’s thought to play a major role in controlling nerve cell hyperactivity associated with anxiety, stress and fear.
You may have heard of other gut signals formed by our gut bacteria – a group of “short chain fatty acids” (SCFA) including butyrate, propionate and acetate. Microbes make these compounds by digesting prebiotic fibre from our diet (that’s one reason we need a variety of fruit and vegetables in our diet, read more here). These SCFA have many functions, including reducing hunger signals to the brain as well as other digestive and mood signals.
What we eat influences the microbes in our gut
What we eat influences the species of microbes in our gut, as well as what those microbes produce in terms of signals to the brain. As the biodiversity of our diet has reduced, the number of bacterial species which reside in our gut has also reduced.
Researchers tracked a cohort of migrants from Asia who had moved to the USA, they measured a reduction in their gut biodiversity as they ate a lower variety of fruits and vegetables in the US than they had in Asia. It is thought this reduction in microbe biodiversity may contribute to increased development of metabolic diseases post immigration (read more here).
New research into treatment of depression
There is new research that shows gut dysbiosis (imbalance) can contribute to poor mental health and depression. Scientists in the MyNewGut consortium, a large collaboration of European researchers, “recommend that patients with depression or vulnerability to depression should be encouraged to enhance a plant-based diet with a high content of grains/fibres and fish” (read more here and here).
Science supports the statements
There is indeed much truth behind the statements “we are what we eat” and “food be thy medicine, medicine be thy food.” Of course, it’s not always easy to eat consistently well – there is a whole new blog in that! But, we can slowly increase the variety of fruit and vegetables we eat, replacing some of the highly-processed food in our diet. It doesn’t have to be all or nothing thinking, small shifts can lead to feeling better and a desire to keep eating well.
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Make sure you check out our new Thrive Gut health and Stability lozenges – designed to promote greater microbe diversity, and enhance digestion – supporting a healthy diet.