There is a two way communication system between the gut and brain, this is one way that gut microbiota mediate our health.
The growing excitement over the role of gut bacteria is being fuelled, in part, by the realisation of the potential role of the gut – brain axis. The gut-brain axis is the hard wiring between the digestive tract and the brain. That is to say a direct communication link passing information between neural, hormonal and immune systems. A key point to make is that the communication is bi-directional, that means the brain talks to the gut and that the gut talks to the brain. Thus the microbiota (gut bacteria) and metaboloites (small molecules that are the product of metabolism) may be in reciprocal communication with different parts of the brain. While this has a direct and obvious impact on processes related to eating and digesting, there is rising evidence that our gut flora may be significant factors in physical and mental health.
The relationship between emotions and the digestive system is one of which we are intuitively aware. For example, feelings of love often manifest as ‘butterflies’ in the stomach. Engaging in team sports enables you to observe pre-match nerves in both yourself and others; the digestive system often plays an obvious role in how some people deal with tension! There is evidence that stress is a mediating component in gut microbiota, perhaps through increasing or decreasing the optimal conditions for certain types of bacteria to flourish.
New studies are suggesting that individual microbiota may be influential in functions as apparently disparate as memory and fear. It is not known what the basis of the relationship is, where the causality can be found. But that there is a correlation between what is in our gut and how we experience life in terms of mental and physical well being. The take home point is that many of the things we eat and drink are able to positively and negatively influence our health. By taking more interest in what goes into your stomach you might do yourself a power of good.
Can memory and stress be altered by what you eat? The evidence suggests it might be possible.
The more scientific research I am exposed to the less inclined I am to expect simple solutions to complex problems. That said, a report from 2015 highlighted in The Guardian was one of the first accounts of probiotics that turned me on to the potential of gut flora to influence different aspects of health and wellbeing. It was reported that participants in an experiment took a capsule containing Bifidobacterium longum 1714 for a month. As a result they enjoyed lower levels of stress when compared to the control group that took a placebo. Stress was measured in terms of the levels of cortisol (a hormone associated with stress) found in the participants.
A second result of the investigation was that when taking the probiotic, memory function also seemed to be enhanced. The people taking part in the experiment took either the placebo for a month or Bifidobacterium longum 1714, then switched. It was a blind test so the participants didn’t know when they were taking the probiotic or the placebo. The effects of the reduced stress and improved memory were described as small but significant, make of that what you will. But the same effects were found in a similar experiment carried out on mice.
I’m not a great fan of experimentation on animals, not because experiments on animals are rarely replicated in a similar way on humans, or that it generally support poor science. Just because its cruel and not very ethical. However as the data exists I will draw your attention to it. Another study from 2015 indicated that B. longum 1714 had a positive impact on mice cognition and an apparent reduction on fear. So one probiotic strain appears to have an influence on both fear and a narrow range of cognitive function (or that both memory and fear/stress have a commonality that can be meditated by B. longum 1714). The fact that both mice and humans appear to have been effected in the same way is interesting. Although these are tentative findings and more studies demonstrating the same effects are necessary (replication).