I listned to this episode of America's Test Kitchen radio yesterday:

Only Ten Percent Human - Michael Pollan and the weird science of your gut

A few notable things from the interview:

- If you take your body and divide it up into individual living cells, only 10% percent of those cells will be human. The rest are nonhuman, microscopic organisms that live in and on you.

- One reason babies born vaginally are overall healthier than babies born by c-section is that vaginal births are dirty. The newborn is covered in blood and secretions and is in turn covered with the mother's beneficial bacteria. Researchers are experimenting with using vaginal secretions from the mother to inoculate babies born by c-section with beneficial bacteria.

- Breast milk contains a sugar that cannot be digested by humans, but research has shown that the indigestible sugar serves as food for beneficial bacteria. Basically a vaginal birth plants the seeds and mother's milk waters the garden.

The interview starts 15 minutes into the show.