Exercised: The Science of Physical Activity, Rest and Health

by Daniel E. Lieberman

The anthropologist Thom McDade has shown that people who grow up in these sorts of evolutionarily “normal,” unsterile environments have different inflammatory immune responses from those of us who grew up with high levels of sanitation. When humans who grew up in pathogen-rich conditions get an infection, their inflammatory response is sudden, strong, but short-lived. In contrast, the immune systems of people who grew up in highly hygienic environments with dishwashers, indoor plumbing, bleach, and lots of soap are different. When they get an infection, their inflammatory response tends to be much slower and less intense and lasts much longer. In other words, too much hygiene, especially when we are young, may predispose us to more chronic inflammation as we age.

Cf ellen and robert