In the last 10 years, interest in the microbiome 鈥� the vast colonies of bacteria and other organisms living in our digestive system 鈥� has intensified, including its possible role in gut complaints such as irritable bowel syndrome. Studies have shown that the faecal microbiota of people with IBS . Some suggest that a course of of developing a functional gut disorder like IBS 鈥� another hint that an .
Some scientists now believe that this imbalance or 鈥渄ysbiosis鈥� seen in IBS , driving people鈥檚 symptoms and the way the brain perceives them.
An unhealthy microbiome might even play a role in the fact that people with IBS are more prone to certain psychological problems such as stress, which in turn seems to further exacerbate their IBS symptoms.
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A recent study that transplanted the microbiota of humans with IBS into mice found that the mice showed not only physical symptoms associated with IBS, such as faster transit of food through the gut and an altered immune response, but behavioural ones too, .
Probiotic promise
The hope is that treating dysbiosis in people with IBS, for example by using probiotics that , could provide relief. The jury is still out, however, on whether probiotics really work. According to one recent study, they could actually prevent bacteria recolonising the gut after a course of antibiotics. Still, for IBS patients, they might help, says Peter Whorwell at the University of Manchester, UK. 鈥淪o I say to patients, 鈥楾ry a probiotic. If it seems to work, carry on with it, and if it doesn鈥檛, try another one.'鈥�
Such research is also spurring the idea that altering the microbiome might bring about changes in mental health more broadly, a field of research termed psychobiotics. 鈥淲e know that during times of stress you produce a state of dysbiosis and that this can contribute to gastrointestinal issues,鈥� says Monika Fleshner, a physiologist at the University of Colorado, Boulder. And we have started to understand that it works the other way too, she says. 鈥淲e can protect that community of bacteria from the impacts of stress, and promote those bacteria in the gut that we know are important for mental health.鈥� Fleshner鈥檚 team has found that a , a brain chemical involved in depression and its treatment.
In a study of 45 healthy volunteers, Philip Burnet at the University of Oxford found that those who took Bimuno, a commercially available prebiotic supplement, for three weeks showed a dip in the stress hormone cortisol. They also performed better in tests of emotional processing: they were compared with people who took a placebo. 鈥淧eople are naturally morbid and drawn to negative things, but those on Bimuno completely reversed this and were more drawn to happy faces,鈥� says Burnet. 鈥淎ntidepressants have been shown to do the same thing and it usually precedes a change in mood.鈥�
He is testing whether altering gut bacteria might improve memory and problem-solving abilities in people with schizophrenia 鈥� common symptoms that don鈥檛 respond to current medication.
Could a gut-targeting supplement or diet ever make sleeping pills or antidepressants unnecessary? 鈥淚 think they鈥檒l be a useful add-on,鈥� says Burnet. 鈥淎longside drug and cognitive therapy, maybe patients will have microbiome therapy.鈥�
As for diet, the evidence points towards variety as being good for you: consuming a wide range of foods nurtures a healthy, diverse mix of microbes. In other words, it鈥檚 time to stop reaching for the same old sandwich.
This article appeared in print under the headline 鈥淚s your microbiome making you sick?鈥�
