This 2019 rodent study investigated diet, stress, and behavioral relationships:
“Gut microbiome has emerged as being essential for brain health in ageing. We show that prebiotic supplementation with FOS-Inulin [a complex short- and long-chain prebiotic, oligofructose-enriched inulin] is capable of:
- Dampening age-associated systemic inflammation; and
- A profound yet differential alteration of gut microbiota composition in both young adult and middle-aged mice.
Middle-aged mice exhibited an increased influx of inflammatory monocytes into the brain. However, neuroinflammation at this stage was not significant enough to manifest in major cognitive impairments.
A much longer exposure to prebiotics might be needed to achieve significant effects, suggesting that supplementation may have to start earlier to be effectively preventative before alterations in the brain occur. This is particularly evident for behaviour.
Targeting gut microbiota, as we have done with a prebiotic, can affect the brain and subsequent behaviour through a variety of potential pathways including SCFAs [short-chain fatty acids], amino acids and immune pathways. All of these are interconnected. Future studies are needed to better deconvolve [figure out] such pathways in eliciting beneficial effects of inulin.
Modulatory effects of prebiotic supplementation on monocyte infiltration into the brain and accompanied regulation of age-related microglia activation highlight a potential pathway by which prebiotics can modulate peripheral immune response and alter neuroinflammation in ageing. Our data suggest a novel strategy for the amelioration of age-related neuroinflammatory pathologies and brain function.”
https://www.nature.com/articles/s41380-019-0425-1 “Mid-life microbiota crises: middle age is associated with pervasive neuroimmune alterations that are reversed by targeting the gut microbiome” (not freely available)
This study’s experiments subjected young and middle-aged mice to eight stress tests. I appreciated efforts to trace causes to behavioral effects, since behavior provided stronger evidence.
I came across this study through its citation in How will you feel?