https://goo.gl/eTzMWT
Now that we know that gut bacteria can speak to the brain — in ways that affect our mood, our appetite, and even our circadian rhythms — the next challenge for scientists is to control this communication. The science of psychobiotics, reviewed October 25 in Trends in Neurosciences, 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.
“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,” says Review lead author Philip Burnet, an associate professor of psychiatry at the University of Oxford. “We’re now on the search for mechanisms, mainly in animal models. The human studies are provocative and exciting, but ultimately, most have small sample sizes, so their replicability is difficult to estimate at present. As they say, we’re ‘cautiously optimistic.'”
Researchers seem to agree that the key players responsible for the bacteria-gut-brain axis — the nervous system of the intestines, the immune system, the vagus nerve, and possibly gut hormones and neurotransmitters (e.g., serotonin and dopamine) — are involved. What varies is the excitement about the use of psychobiotics as methods of treatment for psychological disorders and enhancing cognition. For example, in mice we know that psychobiotics often increase brain-derived neurotrophic factor (BDNF), which is closely linked to learning and memory. At present, we have no way of knowing whether psychobiotics affect BDNF in humans, and a systematic review recently found no overall benefit of probiotic ingestion in humans.