This 2019 rodent study investigated an inulin-type fructo-oligosaccharide (FOS):
“The microbiota-gut-brain axis was used to investigate anti-depressive properties of FOS at the interface of gut microbiota. FOS was introduced via gavage to rats exposed to chronic unpredictable mild stress:
- FOS alleviated depression-like behaviors and repaired intestinal epithelia damages.
- FOS treatment lowered corticosterone level.
- FOS-induced modulation of gut microbiota was more anti-depressive compared to fluoxetine, the standard antidepressant drug.
- N-Ctrl and M-Ctrl were normal and model control groups which received only water.
- N-FOS and M-FOS were normal and model rats administrated FOS (50 mg/kg) [human equivalent (50 mg x .162) x 70 kg = 567 mg].
- M-Flx and M-DP5 rats were model rats given fluoxetine hydrochloride (10 mg/kg) and DP5 compound of FOS (15 mg/kg).
Villi structure was broken for rats in a depression-like state. Mucosal erosion was increased, and the crypt in the small intestinal epithelium was disrupted. Treatment with FOS, DP5 and fluoxetine relieved this damage.
However, a severe side effect was found in the colon of rats that demonstrated apposition to fluoxetine:
- There was obvious goblet cell loss and inflammatory cells infiltration in the colonic epithelium of fluoxetine treated rats, which showed more severity than in model control rats. Although fluoxetine has high bioavailability, its irritation to gastrointestinal tract may cause inflammation reaction thus lead to colonic destruction.
- These pathological changes in the intestine were investigated to compare the influence of stress and possible drug irritation to the gastrointestinal tract. Stress had negatively affected microstructure of the small intestine.
Anti-depressant efficacy of FOS was inseparable from and strongly associated with modulation of the host’s gut microbiota.”
https://www.sciencedirect.com/science/article/abs/pii/S0944711319304738 “Fructo-oligosaccharides from Morinda officinalis remodeled gut microbiota and alleviated depression features in a stress rat model” (not freely available)
Forcing people to learn helplessness explored human equivalents of this study’s chronic, unpredictable stress experiments. Related phenotypes and symptoms in humans and animals include:
- “Social defeat
- Social avoidance behavior
- Irritable bowel syndrome
- Increased hypothalamic-pituitary-adrenal (HPA)-axis sensitivity
- Visceral hypersensitivity.”
These researchers spent a lot of time and effort comparing microbiota categories. The point for people, though, is how we feel.