Mental health and the gut-brain link

Ever wondered about whether there's a link between your gut health and your mental health?

You guessed it - there certainly is - with growing evidence that by improving gut health, we can improve mental health and brain health too!! 

The research around the link between gut health and mental health/brain health focuses mostly on the gut microbiome (although nutrients in our diet also play a big role - see our post on food and mood for more info)

And clinical trials looking at this, have found that by altering our gut microbes, this can alter mental health symptoms and brain health as well.

Gut healthy diets and brain healthy diets are virtually identical, so a common link makes sense, we just haven't known what it is until recent years

These diets are consistently:

✔️high in plant foods (veges, legumes, fruit, whole grains

✔️moderate in healthy unsaturated fat (mostly olive oil, nuts, seeds), and omega 3

✔️low in red meat, ultra processed foods, refined carbohydrates, added sugar and alcohol

Ie the opposite of our ultraprocessed, high sugar Western diets, high in red meat, refined carbs and saturated fat

Gut and brain healthy diets also contain fermented foods (probiotic foods), LOTS of fibre, and prebiotics (resistant starch and complex carbs that our gut microbiome feeds on)

So here's the science behind how it works..

Our brain and body are separated by a layer of tightly connected cells called the blood brain barrier

These filter what gets to the brain, and only allow very small/fat soluble molecules, and some gases through as well as specific larger molecules (such as glucose) via transporter proteins.

The blood brain barrier is vital to protect the brain from germs and toxins, while allowing nutrients to pass through

However this barrier also means that many medications and chemicals cannot pass through, such as serotonin from the gut (happy hormone) 

The gut and brain are also in direct communication via the vagus nerve, which constantly sends signals back and forth

This is a key factor in how stress can cause gut issues, and how stress reduction techniques can improve gut health and symptoms (think of how your gut feels when you are nervous!) 

We don't REALLY know exactly how the gut  brain connection works right now, but the theories are as follows :

✔️gut cells produce most of serotonin in the body, this may affect brain signalling via the vagus nerve (serotonin from the gut cannot pass directly into the brain though)

✔️the majority of the bodies immune cells also reside in the gut, and produce cytokines (chemical signals), which influence neural pathways, and brain inflammation

✔️'good' gut bacteria produce compounds such as butyrate (short chain fatty acids) which can alter the blood brain barrier activity (similar to leaky gut) 

✔️some gut microbes also produce neurotransmitters such as dopamine, serotonin, and GABA

This means that strategies to improve gut health, such as eating a whole food plant focused diet, including fermented foods, reducing stress, getting enough sleep, and getting regular exercise (as well as avoiding foods that harm our gut microbiome) all have the added bonus of improving mental health too. See our gut health section for more details on these.

And it's also why diets designed to improve mental health and brain health (such as the modiMED diet and MIND diet) are very similar to diets that promote a healthy gut microbiome, and are great for gut health too.

It's a win win situation!