Photo by Rick Geary

Smear it on toast, add a shot of Scope to your coffee.

Why does my tube of toothpaste say not to swallow any, and what would happen if I ate a whole tube? — Mr. Chuck Jones, P.B.

Smear it on toast, add a shot of Scope to your coffee, and you can eat breakfast and brush your teeth all at once. A true timesaver. But of course, there it is, printed across virtually every tube of toothpaste on the market, “Do not swallow — use only a pea-sized amount for children under six,” the same wording on every brand. So what’s lurking in toothpaste? Fluoride. In an average-size tube there’s maybe 180 mg, about 178 more than an adult can ingest safely in one sitting. It might not be fatal, but you’d feel pretty punk for a while.

The fluoride in toothpaste (sodium monofluorophosphate) is one of many compounds coaxed out of the highly poisonous and corrosive element fluorine. Other fluorine compounds are handy for etching glass, killing rats and bugs, and making aluminum, steel, unleaded gas, and fuels for atomic energy plants. Teflon and Freon are fluorine derivatives. Mull that over while you’re sudsing those molars tonight.

But toothpaste-type fluoride is somewhat warmer and fuzzier. Small amounts of it occur naturally in sea water and lots of things that you scrub and floss out of your teeth each day — chicken, pork, eggs, potatoes, butter, cheese, and particularly seafood and tea. And we have about two grams in our bodies already, perhaps necessary for bone and tooth formation. Fluoride, either ingested or applied externally, binds to calcium and somehow messes with the process by which oral bacteria convert sugar to acid, which creates cavities. (Doctors treating World War II refugees noticed that people from certain towns had remarkably healthy teeth. The medics identified naturally fluoridated town drinking water as the reason.)

Since 1945, when fluoride was first dumped into a U.S. municipal water supply (Grand Rapids, MI), health officials have been jousting over the medical cost-benefit ratio. One spate of studies warned of long-term dangers of excess dietary fluoride: brown-mottled teeth, skin eruptions, headaches, joint pains, digestive problems, kidney/liver/brain damage, brittle bones, bone cancer, and a variety of neurologic problems, from a generalized hazy goofiness and fatigue to Alzheimer’s disease. The current stand by most physicians, dentists, and public health officials is that the benefits of fluoride far outweigh any risks, virtually none of which have been proved for humans. (Though a few grains of pure fluoride would cancel your need for any more dental appointments, and every other obligation as well — thinking, eating, breathing....)

Adults won’t suffer if they accidentally swallow some toothpaste while brushing, but children are at more risk because of their smaller bodies. If a child should eat a significant amount of fluoridated toothpaste, that would be a medical emergency worthy of a call to a poison control center. And little kids tend to swallow more toothpaste when they brush, hence the warning about using only a pea-sized dab. And here we thought that all we had to worry about was getting the kids to put the cap back on.