Stress

Stress “disrupts” the gut microbiome.

This Nature.com paper studied students under exam stress, giving half of them a fermented milk with Lacticaseibacillus rhamnosus CNCM I-3690. The other half got a placebo milk. What was surprising wasn’t that the probiotic helped, but how. It didn’t flood the system with good bacteria or overhaul the microbial landscape. 

Instead, it preserved structure. Alpha and beta diversity stayed more stable under stress in the probiotic group. Providing more of a 'buffer' than a 'fix'. After 4 weeks, L. rhamnosus became a central node in the community, with tighter links to butyrate producers like Faecalibacterium and Coprococcus. By exam day, it had quietly rewired the ecosystem.

So maybe the real value of some probiotics isn’t in what they add, but in what they prevent from unraveling.