• Nichole Sullivan BSc Psych (hons) AHPRA

Do Donuts Really Make Me Happy? Mental health and the gut microbiome


I've been asked by a lot of 'probiotic', 'kombucha' enthusiasts or critics, how exactly does the gut microbiome affect mental health? Is the secret to unlocking good mental health in the gut? Does food affect mood? Are ‘gut feelings’ a real thing?

Here’s the science simplified.

Our diet affects the delicate mix of Microbes in the gut. If we eat well, that mix produces a state of balance (homeostasis). When we achieve this balance, the body works on optimistic functions. Optimistic functions, are those which assume we are going to live longer. For example, we produce collagen for our skin, enamel for teeth, our hair gets shiny, we produce Seretonin (a chemical which makes us feel good). Seretonin puts us in a 'good mood', it determines our appetite, enhances our memory, and aids in development of good, restorative sleep. The opposite occurs as well.

If we eat poorly, say for example, we binge on donuts, then our gut is off balance, we need to produce more insulin. The brain is an insulin-sensitive organ. Insulin impairs our ability to cope with stress, but how? Insulin crosses the Blood Brain Barrier (BBB) into the hypothalamus and we move out of homeostasis into the primitive stress response. The Hypothalamus starts our fight or flight response to metabolise all the sugar. Insulin moves into the hippocampus (responsible for memory), and into the parietal cortex (which controls sensory perception) and into frontal cortex (controls your ability to calculate sums in your head, think on your feet, or weigh up pros and cons). All these functions are impaired by excess insulin. Essentially our brain function gets smooshy. <<< highly technical term meaning sluggish and mooshed together.

Two studies have linked good diet to prevention of mental illness, however the sample sizes (4000) were too small to really excite (convince) the academic community. The Mediterranean Diet in particular has been linked to prevention of depression.

The brain and the gut are currently linked (in the academic literature) via the immune system. Therefore, we eat well, this affects microbes in the gut, this affects our immune function, we stay healthy and fight disease, and we feel good. We think there may be a more direct link; via direct neurons which originate in the brain and connect down deep in our gut, but we haven't proven this yet.

We DO know that there are neurons in the gut (specialised brain cells previously thought to only occur in the brain). We have also found that Seretonin is produced not only in the brain, but in the gut as well. We just haven't mapped a direct route between these neurons, this Seretonin, mood and behaviour... YET.

Are some of our feelings, originating in the gut? Well yes, however, we’re waiting to map a more direct route as they currently route through the immune system, and thus it is kinda like a slow speed dial up connection, or stopping over in Melbourne on the way to Hobart.

So food does affect mood.

Is the secret to unlocking good mental health in the gut? I'm confident it will be a much greater focus over the next 5 years, we will learn that food is just as good as exercise and medication in keeping good mental health. Our Workplace Mental Health consultancy focuses on Nutrition, Exercise, Sleep and Social Wellbeing as the foundation of good mental health at work.


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