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Our bacterial passengers don’t outnumber us after all

 •  • by Paul Ingraham
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Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

Ever hear that we have vastly more bacterial passengers than cells? Yeah, me too. Ever blithely repeat that myth to a large Internet audience? Yeah, me too. But now corrected, in two articles: We Are Full of Critters and Ten Trillion Cells Walked Into a Bar. For an explanation of how the myth was busted, see Scientists bust myth that our bodies have more bacteria than human cells.

Although I have repeated the myth, I have frowned at it suspiciously several times. I’ve always thought it was obvious that mass had to be considered for it to be meaningful, which is why I particularly like this diagram.

Chart showing cell populations in the human body.
I also always assumed that most of the bacteria surely had to be in the poop chute, which isn’t such a fun fact. The idea that we have more bacteria than cells sort of implies symbiosis on a vast scale, bacteria everywhere, which is true in a way … but the bacterial populations outside the gut are really quite small compared to our own cell populations.

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