Gut feelings: Buttery secrets of the microbiome

There have been rumbles in the scientific, health and medical communities for some time about the importance of gut health and the gut microbiome. Links have been made between gut health and diabetes, asthma, cystic fibrosis and heart disease, among myriad other illnesses. Recent research published in Nature Microbiology has unearthed new evidence supporting a potential link between gut health and mental health – one of the most controversial fields of microbiome research.

The gut is the gastrointestinal (GI) tract: the small intestine, large intestine and colon. The gut microbiome is made up of the microorganisms (microbiota) that live in the GI tract. These microbiota outnumber the other cells in the human body by a factor of 10, and contain more than 100 times as many genes. Little wonder then that the microbiome is often considered to be a human organ of its own accord. Your microbiome is typically formed early in life, concurrent with the development of your immune system. Diet, exercise, and lifestyle factors can all influence its composition later in life, but only marginally. The early years, as is true for so many aspects of healthy functioning, are the most critical.

We have long known that the gut can communicate with the brain via the enteric nervous system (ENS), that the gut houses neurotransmitters like serotonin that influence our mood and well-being, and that physical signs of emotional arousal are often the result of sensations produced by the ENS; for example, ‘butterflies in the stomach’. What has been less clear is whether the balance of certain bacteria in the gut may actually influence our mental health or contribute to the presence of mental illness.

This most recent study in Nature Microbiology uses population-level data from the Flemish Gut Flora Project, and is one of the first large-scale studies to examine how bacteria in the gut influence mental health. Using the microbiome data collected from the faeces of 1054 individuals, the research team found that levels of Coprococcus and Dialister bacteria were depleted in people with depression. In turn, people with higher levels of Coprococcus and Faecalibacterium reported higher quality of life. Coprococcus and Faecalibacterium are both responsible for the production of butyrate. Haven’t heard of butyrate? Oh, you will.

Butyrate is the rising star of gut health, with evidence constantly accumulating that this anti-inflammatory compound is responsible for all kinds of good things. When bacteria in the gut (like our good mates Coprococcus and Faecalibacterium) have certain high-fibre foods to feast on, they produce butyrate. They prefer foods high in soluble fibre, so food like oats, nuts, seeds, and beans are at the top of their list/menu. Good news for butter lovers – butter is the best food source of natural butyrate! In fact, butyrate is Latin for ‘butter’. Butyrate has been shown to reduce inflammation in the gut and contribute to improved brain health and mental health, including the promotion of cell regeneration and the slowing of neural degeneration.

The last time I wrote about microbiome research I added a disclaimer about being conservative when interpreting any findings, or when reading someone else’s interpretation, and I feel compelled to do so again. The number of species examined in microbiota research are so vast that finding a spurious correlation between the levels of certain bacterium and some aspect of health is almost inevitable, regardless of how thorough and cautious the research team have been in conducting and reporting the findings. In the case of the researchers that published these most recent findings in Nature Microbiology, they were both thorough and cautious.

They used a large sample, and they validated their findings against two independent samples. But the warning still stands – interpret with caution! Research of this kind can only really tell us with any certainty that a relationship exists between two things; it can never tell us that one thing causes the other to happen.

It may well be the case that changes in the gut influence changes in the brain and mind, but it is still too early to be certain. If this is the case, then it reveals a brave and exciting new avenue for mental health treatment; psychobiotics. In the meantime, I’m happy to just put extra butter on my toast.

Dr Jessica L Paterson is a Senior Research Fellow at CQUniversity, Appleton Institute

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