It wasn't so long ago that the idea of swallowing bacteria on purpose in probiotic drinks like Yakult was considered extreme.
But time and time again, science has shown beneficial bacteria like those found in fermented foods can affect our circadian rhythms, immunity, digestion and skin.
Enter a resurgence in bacteria-rich foods like sauerkraut, kombucha and kefir.
Yet the gut-brain link has only just started to be understood and University of Oxford associate professor Philip Burnet says it has led to the new field of 'psychobiotics'.
"Those studies give us confidence that gut bacteria are playing a causal role in very important biological processes, which we can then hope to exploit with psychobiotics," Burnet said.
In the journal Trends in Neurosciences, Burnet and his team said the field "explores emerging strategies for planting brain-altering bacteria in the gut to provide mental benefits and the challenges ahead in understanding how such products could work for humans," as well as prebiotics that encourage beneficial gut bacteria.
Basically, it's attempting to treat mental health via the bacteria in your gut.
He said there were a plethora of ways to alter gut bacteria -- from foods to exercise.
"Prebiotics -- nutrition for gut bacteria -- are another channel to alter gut bacteria," Burnet said.
"We call for an even further widening of the definition of 'psychobiotics' to include drugs such as antidepressants and antipsychotics, and activities such as exercise and eating, because of their effects on gut bacteria."
However, Burnet said they are nowhere near being able to do away with medication in favour of the right strains of bacteria.
"Psychobiotics are a long way from their true translational potential," Burnet said.
"It's a little boring to say that we need more studies, but that is always the case in any academic discipline.
"The technology and resources already exist for such investigations, so though we are enthusiastic, the enthusiasm needs to be tempered and channeled toward answering the core mechanistic questions."