Approximately 50% of small molecules in human blood originate from or are metabolized by gut bacteria.

“in a sort of the discovery that many of our metabolites in our blood probably a third or more maybe from microbiome in other words when you check your blood test for checking human analytes but when you actually start to do some more sophisticated metabolic testing and metabolomic you find all these things that aren't human they come from bacteria that are regulating your immune system that are activating your your mitochondria that are regulating your DNA that affecting your brain chemistry affecting your mood affecting all sorts of diseases”