This week’s New Yorker includes an interesting article by David Owen on the rise of the pervasive hand sanitizer Purell. The story comes on the heels of the Globe’s own look at the science of hand-to-hand disease transmission. It also quotes a food expert with a startling perspective on human health.
The expert is Don Schaffner, a food microbiologist at Rutgers. He says that germophobia in rich countries like the United States leads to weaker adult immune systems and has a negative impact on long-term health. Here’s the quote:
We might have a much healthier population if we adopted the kinds of conditions that we see in many Third World countries, with poor-quality food and poor-quality water and lots and lots of germs. If we did that, we would have very healthy and very strong immune systems. Unfortunately, the price that we would pay would be extremely high infant mortality. That's the trade-off.
The broad idea he’s talking about is known as the “hygiene hypothesis,” the notion that the cleanliness of modern life actually weakens our immune systems. The hygiene hypothesis has a strong counterintuitive appeal – fighting disease makes your body healthier! - and has been particularly influential in certain corners of American parenting, where a lack of early exposure to germs is blamed for many modern woes, including autism.
But is it true? Would we actually be healthier if we were exposed to more disease? As it turns out, a number of well-respected studies have found that poor health in childhood is highly correlated with poor health in adulthood. A 1998 study by Samuel Preston at the University of Pennsylvania looked at a large group of African-Americans born at the beginning of the 20th century. He found that the children who grew up in the least healthy environments were the least likely to survive to age 85. A 2007 study by Steven Haas at the University of Arizona came to similar conclusions, finding that “early life health and socioeconomic circumstances have lasting impacts” on health as people age.
Why would this be? Perhaps people who grow up in less healthy environments also tend to live in less healthy environments as adults. Or, perhaps the hygiene hypothesis has it backward, and exposure to disease in childhood leads to permanent health handicaps as people age. That’s the argument of a 2004 paper published in Science titled, “Inflammatory Exposure and Historical Changes in Human Life-Spans.” The authors argue that childhood infections cause a buildup of inflammation in the body, which leads to higher rates of cardiovascular and respiratory diseases, cancer, and diabetes in adulthood.
I emailed Schaffner about all this, and he promptly backed away from his quote in the New Yorker, explaining that his was an “off the cuff” comment pertaining to a field where he’s not an expert (“I'm a food microbiologist, not a child health/mortality expert”). He also said that while cleanliness may have fewer downsides than he thought, the idea that illness in childhood promotes health in adulthood still seems “sensible” to him.
Which is just the thing. It makes a certain kind of intuitive sense that, when it comes to childhood germs, whatever doesn’t kill kids only makes them stronger. But empirical evidence suggests otherwise. Childhood germ exposure likely comes at a lifelong cost, and it turns out we should be grateful we live in a country with good hygiene standards.
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Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.
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Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."
Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.
Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.