Science is revealing more about the link between gut bacteria and mental health…. But what does this mean for us? How do we apply current knowledge of gut bacteria to our psychological well-being ? Here’s a summary of what we know, and what we have yet to learn:

 

What is the Microbiome?

The “Microbiome” are bacteria, fungi and viruses found in the lower intestines. We have about 300 to 500 different kinds of gut flora making up up 1-2 kg of our body mass. Each person has a unique microbiome – much like a fingerprint – which are partly inherited, and party influenced by factors like diet. These microbes are essential for our immunity and digestion. Advances in DNA technology are helping us understand their complex relationship to health – including brain function.

 

Our gut – The Second Brain

Humans have a gut-brain axis – some calling the gut our “Second brain”. Research suggests changes in our microbiome might improve mental health. Certain strains of intestinal bacteria have been linked to autism, depression and anxiety (Clinics & Practice, 2017) . But the exact nature of the relationship between gut flora and brain function is not clear. Unfortunately we don’t have much conclusive data about treating mental illness through the microbiome yet.

Typically our gut health can be thrown out of balance by antibiotics, alcohol, processed foods, and medications. Treatment for microbe imbalances can include probiotics, changes in diet, and even faecal matter transplants.

What about probiotics?

We can take probiotic supplements but these “good bacteria” also occur naturally in our diets. Fermented foods like yogurt and kimchi are high in probiotics which can aid digestion, metabolism and in some cases even weight loss. Essentially, we are still exploring the connection between these microbes and psychology. But above all diet seems to have the strongest impact on gut flora (well beyond that of probiotic supplements).

When looking at the symptoms of people with anxiety taking probiotics, the benefits on mood were only marginal. An overview of twenty-one studies (General Psychiatry, 2018) found probiotic treatment improved anxiety symptoms in 36% of cases. But non-priobiotic treatments (eg: diets high in fresh produce, and restrictions on processed fibre and sugar) showed an 86% improvement. This doesn’t mean we should dismiss probiotics as a way to help our mental health. But it shows relying on supplements alone may be no substitute for dietary changes.

 

Gut Bacteria and Mental Health – Final Thoughts

Our bodies usually suffer when we are under emotional stress. Mental illness often means struggling with physical activity and nutrition. The Flemish Gut Flora Project (Nature Microbiology, 2019) found two strains of gut bacteria were common in people with high quality of life… but lower in those with chronic depression. But crucially, these findings do not prove depleted bacteria causes depression. It may be that depressed people are less likely to have balanced gut health because their symptoms impact lifestyle, diet and brain chemistry.

We do know gut flora interact with the neurotransmitters responsible for mood. With this in mind, people with mental illness should be aware they are more prone to imbalances of the gut. Some helpful strategies may include changing your diet or taking probiotics. Future research will likely bring new insights on treating mental health by looking at the lower intestine, not just the brain.