[manmal]

Yeah, many diseases are related to the microbiome (although there is the question of where does the cause/effect arrow point?), but current probiotics are for the most part not sticking around in the gut. The usual suspects just have an indirect effect on the bacteria you already have, and get excreted within days/weeks. Spore forming bacteria survive longer, but might become a problem of their own if overpopulated. Also.. if your goal is a more diverse microbiome, then supplementing the most abundant L-bacillus strains might not be a particularly effective option?

And the microbiome is so vast that it’s hard to influence on the long term. With a very strong probiotic you get 5 * 10^10 bacteria (of which most die in the stomach and small intestine), but at the same time you have 3.8 * 10^13 native bacteria settled and accustomed to your body, feeding on the sugar you have just eaten. You need a lot of those tablets to have a meaningful impact.

Just like a great body, a great microbiome gets made in the kitchen. AFAIK dietary changes work way faster than popping probiotics. With the exception that you are missing certain strains (eliminated by antibiotics?), which should be replaced.