05/30/2013 02:36 EDT | Updated 07/30/2013 05:12 EDT

Is the Meth-Mouth/Diet-Soda Study Really Science?

Academy of General Dentistry

Is drinking diet soda as bad for your teeth as doing meth or crack?

"Yes!" says a new study published in the General Dentistry journal -- and the dozens and dozens of headlines eagerly referencing the same.

Does that finding sound a little suspect?

It did to me.

I know at least a couple serious Diet Coke swillers (breakfast, lunch, and dinner!) who may be consuming obscene quantities of caffeine and aspartame, but still have gleaming pearly whites. They certainly aren't afflicted with meth mouth. So what gives?

Your acquaintances constitute a sample of two, I told reminded myself. That's hardly a scientific examination of the phenomenon.

Whoever did the study that all these articles are alluding to would have examined reams of subjects and data, right? Otherwise the surprising findings wouldn't be appearing on so many media outlets, including CBS News, ABC News, Fox News,, The Toronto Sun, NPR, and, yes, The Huffington Post.

Not right.

If you read past the headlines, you'll learn that the "study" everyone is talking about happens to be barely more scientifically rigorous than my "but I have a couple friends..." analysis.

The diet-soda-is-like-meth conclusion was arrived at based on a total sample of three people. There was one meth user, one cocaine user, and one person who drank more diet soda than even my Diet Coke-addicted pals -- about 2 litres every day for three to five years. All three individuals experienced similarly severe, disgusting tooth erosion that required having all their teeth extracted. And... well, and that's about it. Oh, except for the added detail that none of them went in for regular dental care -- the diet soda drinker hadn't seen a dentist in over 20 years.

This is not science, people. It's an interesting anecdote. The fact that it's being reported on as though it's definitive proof of diet soda being as bad for teeth as meth is troubling. Our instinct to see the word "study" and assume that whatever follows is a scientifically established conclusion is going to get us into serious trouble one of these days.

In the grand scheme of things, people drinking less diet soda because they mistakenly think it's been proven to cause all their teeth to fall out, isn't going to do much harm to anyone but the beverage industry. And the beverage industry will survive. But the lazy and credulous thinking that underlies such conclusions -- and the behaviour choices to which they lead -- carries over into more crucial decisions too, such as whether to vaccinate a child or to grow genetically modified rice with Vitamin A that could save millions of lives. (In these areas, fears based on shaky claims -- of vaccine-autism links and GMOs causing birth defects -- have led to the resurgence of measles and preventable cases of blindness, respectively.)

The critical eye needed to distinguish dramatic individual incidents from evidence-based proof of general causation is being lost. Colourful examples are being confused with comprehensive data. The result? We're becoming a society that fails to take positive actions because our heads are so easily turned by anecdotal horror stories. And we turn to dubious quick fixes for the same reason. ("Carol's brother's cancer was cured completely by homeopathic remedies and he never had a recurrence.")

Why this is a problem: In more and more areas of life, we're complaining about people not making "smart choices." We want people to eat better so we won't have to deal with the costs of an obesity epidemic. We want people to exercise appropriately so our healthcare system won't be overrun with cardiac care costs or hip replacements. We want people to vote for politicians who propose sound environmental policies so that we can maintain healthy planets and economies. We want people to sit as responsible jurors who weigh evidence carefully so that guilty people are convicted and innocent people are not.

But people can't do any of these things successfully unless they have a baseline of scientific literacy with which to critically evaluate the claims that bombard them. Whether it's a defense attorney insisting DNA findings exonerate his client, or a TV ad for a nutritional supplement promising dramatic weight loss, the bottom line is that without a basic understanding of what qualifies as objectively persuasive, credible evidence, people are doomed to make damaging decisions. When these decisions involve carbonated beverages, there's little harm done. When they involve sending an innocent man to prison or exposing a vulnerable population to rubella, there's a real problem.

Maybe we can use this diet soda meth mouth story as a wake-up call about how apathetic we've become about questioning what we're told. The next time we read about a study with a shocking finding, perhaps our first move will be not to write a hysterical headline or email, but instead to pause and ask things like, "How big was the sample?" and "What factors did they control for?" and "Were the subjects chosen at random?" Regardless of the answers we come up with, it'll be good exercise for the critical thinking muscles we need to responsibly navigate modern life.

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