Arlo and Janis by Jimmy Johnson for February 07, 2013

And yet the air in your head weighs nothing, Janis.

It’s not stars in the universe. It’s human cells in the body. Bacteria are so much smaller than human cells that it takes more of them to weigh 3-5 pounds than enough human cells to weigh 150-200 pounds. It’s one of those gee-whiz stats that only impresses people who have a low level of numeracy and a poor level of scientific understanding.

What really matters is that the commensal bacteria that live in and on the human body have important roles to play in our physiology. They make direct and important contributions to our health. We need to be aware of that when we dump a pile of antibiotics into the system without thinking through the fact that doing so will have costs as well as benefits.

In recent months Scientific American has run some good materials on this. I’m sure a little Googling will turn up more good stuff as well among the usual welter of web-based dreck.

For those who do enjoy gee-whiz stats, the 100 trillion or so bacteria in the human body are about ten times as numerous as human cells, and about a thousand times as numerous as the merely ‘billions and billions’ of stars (as the innumerate and easily impressed Carl Sagan used to say) in the Milky Way galaxy.It’s certainly true that everyone should be more aware of the implications of antibiotics, especially the broad-spectrum kind; certainly physicians in my experience are grossly ignorant of the issue, and in this as in so many areas of health care the caveat emptor principle applies more than is generally acknowledged.By the way, the effects of bacteria in our bodies may go beyond their interaction with our individual selves. They seem to have swapped genetic material with the human genome over the millennia.

The strip I understand . . . it’s some of the comments that baffle me.

RE: comment/strip understandingYes, lots of probiotics in and on us. We’d die without them. So while Janis is happy to think that “she” is scale -3 lbs, she might as well say that without a liver she’d weigh 3 lbs less.