Saving the Five-Second Rule

The five-second rule (or three-second rule, depending on whom you ask) was publicly discredited a few months ago after an incident involving the Ohio State basketball head coach, a piece of chewing gum, and the ground. But an exciting new study contradicts that fateful Chicago Tribune story, and Harold McGee is spreading the news, potentially rescuing the five-second rule from the dustbin of schoolyard lore.

As he explains, researchers at Clemson University conducted “a thorough microbiological study” of the rule, which stipulates that if you pick up a dropped piece of food within five seconds, you can eat it without worrying about germs. While it may have originated on the playground, the rule actually has a basis in reality: The researchers found that the longer they let food rest on bacteria-painted surfaces (they used a salmonella “broth”), the more germs the food collected. The difference is vast, in fact:

On surfaces that had been contaminated eight hours earlier, slices of bologna and bread left for five seconds took up from 150 to 8,000 bacteria. Left for a full minute, slices collected about 10 times more than that from the tile and carpet, though a lower number from the wood.

We don’t actually eat off of surfaces that have been bathed in salmonella all that often (or for that matter E. coli, which another five-second-rule study had used as a test bacterium), so our floors and countertops are generally far less contaminated. Still, McGee cautions, a dropped piece of food on a normal floor “would be likely to pick up several bacteria.” Some strains of salmonella can cause illness with as few as 10 bacteria, and the deadly strain of E. coli with fewer than 100, so just watch where you go smearing your raw chicken juices.

But if you clean off your counters after preparing meat or eggs and don’t make a habit of tracking dog poop all over your floors, the five-second rule will probably keep you safe. Certainly safer than if you let dropped food linger any longer before putting it in your mouth—and now there’s science to prove it. Thank you, science!

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