This is not a question most people ask of themselves, and those that should don’t think to ask it.  It’s left to us parents to wonder: How many Crest commercial brushloads can my kid eat before I should worry about the fluoride?  Here’s a calculation to help answer that.

The safety data I’m using is from the 2013 article by the European Food Safety Authority EFSA, Scientific Opinion on Dietary Reference Values for fluoride.  They state that regardless of age and condition, the adequate intake is 0.05mg per day per kg of body weight.  For a 20-kg person (44 lbs), that works out to 1mg per day.

How much toothpaste to get to 1 mg?  It depends on the toothpaste.  Most toothpastes have an indication of fluoride ion content.  We have a children’s toothpaste (Elmex) which states 500ppm fluoride ion, and a regular toothpaste (Crest) that indicates 0,15%.  Our fluoridated table salt contains 0,025% fluoride.  This works out to 2g of toothpaste for Elmex, 0,7g for Crest, and 4g of table salt.

That’s all very well, but few people visualize grams well.  For the salt, an online converter tells me we’re looking at 0,7tsp.  My not terribly precise kitchen scale indicated that for the Crest toothpaste, it corresponds roughly to one TV commercial brushload; for Elmex, to three such brushloads.

And then there’s tea… which weighs in at anywhere between 1.5mg/liter to 4mg/liter, perhaps even more, depending also on whether your water is fluoridated.  AcneEinstein has a more detailed treatment of the tea question, which also links to WHO guidelines that seem to only partially square up with the EFSA guidelines.

The upshot: monitor and train your kids, but don’t freak out if they eat a little toothpaste.  And don’t raise them exclusively on iced tea…