human microbiome

Probiotics are one of the recent darlings of the supplement world. But do they do anything? A small human study says yes. But what they do isn't good.
When I was still in school, the rule-of-thumb for the human microbiome was that bacteria outnumbered human cells 10-to-1. Not so, say the authors of a new PLoS Biology paper, who re-crunched the numbers. According to their estimate, the ratio is much closer to 1-to-1.