Imagine if microbes could make you smile. Plenty of new research suggests that unhappiness, at least in the guise of depression and anxiety, may stem from the gut-brain axis and what transpires along the route.
A new paper describes the many challenges inherent in the intricate science and suggests a way forward. Gregor Reid of Lawson Health Research Institute in Canada laid it out recently in Disentangling What We Know About Microbes and Mental Health in Frontiers in Endocrinology journal.
The premise of Reid’s paper is that mental health may indeed be influenced by our microbes. He describes the intriguing evidence in comparing lifestyle of African hunter-gathers and those of western populations. The exposure to pathogens and parasites as well as more natural foods in the Africans typically promotes a different microbial map than in the west. An exception to this: The vaginal microbiota appear to share the same Lactobacillus strains across continents.
Lifestyle and diet do alter the microbiota. Current studies suggest probiotics may alter microbes and thus reduce anxiety and depression.
But Reid wants to know which microbes are critical to happiness.
“The possibility that vast numbers of microbes in the intestinal tract with the potential to produce compounds that include neurochemicals can influence the brain is compelling.”
Unfortunately, pinpointing which microbes are effective is difficult. And much of the research has been in animals or less rigorous studies in humans.
In a discussion of autism and premature conclusions, Reid writes:
“The basis of too many microbiome studies, to date, has been rodent experiments, or observational studies in humans, neither of which prove cause and effect.”
There are attempts to translate rodent studies to human study as was done with a bifidobacterium strain that was found to normalize anxiety-like behavior in mice and showed some success— six years later– in humans with irritable bowel syndrome linked depression. The improvements were related to changes in brain activation patterns indicating that this strain of probiotic reduced limbic reactivity.
Reid covers other pertinent topics:
- Methodological challenges concerning data sets and confounders
- Growing cynicism in the probiotic field
- Socio-economic status and environmental pollutants as confounders