Evolution carved out a special place for anxiety, an often helpful emotion which triggers cortisol release in fight-or-flight responses.
Anxiety can save your life.
But these days anxiety from uniquely modern stressors—health screenings, computer meltdowns, traffic jams, noise pollution and hundreds of other adverse events —lingers long after its usefulness.
Chronic anxiety can kill you.
This steady stream of stress damages health across the spectrum including the newly recognized microbiome-brain-gut axis. The axis operates as a bi-directional pathway or two-way street: gut microbes influence the brain nervous system programming and signaling which can make a U-turn and drive impact back to the gut microbiota.
Stress responses may provoke changes in gut microbiota. Many animal studies demonstrate the connection. In one study, social stressors reduced the relative abundance of Bacteroides, while increasing that of bacteria from the genus Clostridium.
And microbial state may impact the stress response. For example, mice fed broth laced with Lactobacillus rhamnosus were less likely to be anxious or stressed and produced less of the stress hormone corticosterone than control mice that drank a bacteria-free broth. Germ-free mice showed exaggerated hypothalamic-pituitary-renal (HPA) stress response which was reversed with Bifidobacterium infantis. And in another, strains of Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus helveticus, or Lactobacillus rhamnosus, either alone or in combination, have normalized behavioral phenotypes in animal anxiety models, according to a 2014 review.
Homo sapiens too respond with less anxiety when treated with probiotics. Beneficial psychological effects were seen in adults given both Lactobacillus helveticus and Bifidobacterium longum for 30 days. And compared to controls, a small sample of women given a fermented probiotic cocktail for four weeks displayed changes in activity of brain regions that control central processing of emotion and sensation.
A 2016 review of ten randomized control trials found that probiotic supplementation did reduce anxiety by various degrees.
Neurobiologists are searching for how this all works.
Possible mechanisms of action include:
- Modulation of the hypothalamic-pituitary-adrenal axis
- Immune system activation
- Production of metabolites
- Vagus nerve changes
Should we replace sedatives with probiotics? It’s too early in the research to make an accurate prescription, but it won’t hurt to add more fermented foods to your menu and augment it with a probiotic supplement.