“Everything You Know Is Wrong” is the prospective title of a book I’ve long wanted to write about why the conventional wisdom about everything almost invariably turns out to be wrong. We’re seen it with all manner of diet advice, such as salt, low-fat fads, and so forth. (Turns out there are already a couple of books with this title and similar themes, so I’m late to the party I guess. And there’s even a Weird Al Yankovic parody tune by this title.)
The latest bit of conventional wisdom to end up on the ash heap is . . . flossing?
The federal government has recommended flossing since 1979, first in a surgeon general’s report and later in the Dietary Guidelines for Americans issued every five years. The guidelines must be based on scientific evidence, under the law.
Last year, the Associated Press asked the departments of Health and Human Services and Agriculture for their evidence, and followed up with written requests under the Freedom of Information Act.
When the federal government issued its latest dietary guidelines this year, the flossing recommendation had been removed, without notice. In a letter to the AP, the government acknowledged the effectiveness of flossing had never been researched, as required.
The AP looked at the most rigorous research conducted over the past decade, focusing on 25 studies that generally compared the use of a toothbrush with the combination of toothbrushes and floss. The findings? The evidence for flossing is “weak, very unreliable,” of “very low” quality, and carries “a moderate to large potential for bias.”
So have we all just been consumer victims of the flossing-industrial complex? More and more it seems that Woody Allen’s Sleeper was a documentary: