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So much for flossing – and for the tyranny of expertise

Floss much? Me neither. I'm a flossing slacker. For 40 years, I've dreaded going to the dentist, because I know I'll get a lecture about my oral hygiene. Mine is flawed. I always wildly exaggerate the amount I floss, but I know they know I'm lying. After every gentle scolding from some 30-year-old hygienist, I slink away feeling like a naughty child. I vow to do better before my teeth fall out. But, somehow, I never do.

Now the secret is out. Flossing is a waste of time. Despite decades of advice from the entire dental and public-health establishment, there's not a shred of scientific evidence that it cuts down on tooth scum or prevents gum disease and cavities. I scarcely know whether to be relieved or outraged – relieved because I'm off the hook, or outraged because they've bullied and shamed us for so long, and for nothing.

Mind you, this is hardly the first time. A comprehensive list of the experts' flawed health advice would take up volumes. Dietary fat is bad for you (wrong). Ditto cholesterol (wrong). Exercise will help you to lose weight (wrong). A low-fat diet will help you lose weight (wrong). Breast-feeding your infant is vastly superior to bottle-feeding (wrong). Salt is bad for you (wrong). Whole milk is bad for your kids (wrong). Being moderately overweight is bad for you (wrong, wrong, wrong). You get the picture.

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To be sure, a lot of this advice seems intuitively correct. How can it be wrong to cut down on fat – or to floss your teeth? And in fact, it's not wrong. It's just that following this advice does not confer the promised benefits. The trouble is that we've internalized this advice so much that we can't help feeling guilty when we disobey it. In our increasingly secular society, good health habits are the equivalent of religious observance. Every unflossed tooth and every scoop of Haagen-Dazs is a measure of our sin.

Like a lot of health beliefs, our belief in flossing turns out to be faith-based. The truth was exposed this week by the Associated Press, whose reporter Jeff Donn dived into the scientific evidence and found that it was scant to non-existent. Instead, he found piles of research showing that the evidence for flossing is "weak, very unreliable," of "very low" quality and carries "a moderate to large potential for bias." He asked the U.S. government to justify its guidelines about flossing. By law, dietary and health guidelines issued by the government must be backed by scientific evidence. The government could not. It has now quietly dropped its flossing advice.

Not surprisingly the dental establishment is sticking to its guns. Its response: Keep on flossing! After all these years, it would be awkward to admit that its flossing fetish is misplaced. "Flossing is an effective preventative measure …," insists the Canadian Dental Association. "The weakness of the evidence … is a reflection of the difficulty of conducting the necessary studies, not of the value of flossing for the maintenance of good oral health," the association told Global TV. A spokesman for the American Dental Association blamed the weakness of the studies on research participants who don't floss correctly.

In truth, good studies are hard to get not only because they would require huge numbers of participants over many years, but also because hardly anybody flosses correctly. Most of us might as well attack our gums with piano wire. And hardly anyone, apart from dental hygienists, is compulsive enough to floss every day. In other words, flossing's not the problem. People are the problem! Which is exactly the reason 800-calorie diets don't work either.

In Britain, they don't have a flossing fetish, and they're bemused by ours. "The British dental profession gave floss a quiet burial years ago," dentist Ollie Jupes wrote this week in The Guardian. "Even in controlled studies, after instruction, the patients taking part couldn't floss properly. I know of no dentist who flosses. Not one." To get out those bits of foods that lodge between your teeth, he recommends an interdental brush. (Toothpicks come in handy too – although using them in public may mark you indelibly as lower class.)

The uselessness of flossing, in these dark and stormy times, is a bit of welcome news. Don't let your dentist guilt you out, ever again. I feel better about myself already, and I hope you do too.

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