Rosemary Donahue
June 14, 2016 12:31 pm
Getty / Manfred Rutz

We’ve all heard it before. Many of us have said it, even desperately, when something we’re about to eat falls on the floor: “FIVE-SECOND RULE!” It’s often taken as the gospel truth, but how true is it really? It turns out, there’s only one study that has ever been published to settle the matter. It was conducted by Dr. Paul Dawson — a professor at Clemson University.

You can read the full study in depth over at CNN, but we’ve distilled it for you here:

The myth of the origin:

It originated from a high school student named Jillian Clarke and her buddies when they inoculated floor tiles with bacteria. They then put gummy bears and cookies (y’know, high schooler food!) on the tiles for varying time periods and studied to see how long it took for the bacteria to reach the food. Would you guess how long their calculations told them? Yup, five seconds! There used to be a myth that the rule came from Julia Child, but this is the true story. Now you know!

Dr. Dawson’s study:

Okay, so how long does it take, really? That’s what Dr. Dawson (and the rest of us!) wanted to know, and he and his colleagues actually conducted a study similar to the study Clarke and her friends conducted (but just a tad more advanced). However, they used different kinds of floor tiles — carpet, wood, and tile. They inoculated them with Salmonella, and then placed either bread or bologna on them for five, 30, or 60 seconds. They then repeated this experiment after the bacteria had been on the tile for two, four, eight, and 24 hours — basically, this was a very thorough study, and accounted for a LOT of variables.

So, what did they find?!

Basically, they found that the five-second rule is pretty much bogus (sorry, everyone!). They found that it didn’t matter how long the food was on the floor — what mattered more was how much bacteria was on the floor to begin with, and that amount decreases after the initial inoculation. They did find, however, that carpet is a much better place to drop food than wood or tile is. Bacteria transfer was less than 1% on carpet, but between 48-70% on wood or tile (or, that stuff all kitchen floors are made of…).

What does this mean?

It means that the five-second rule isn’t really a “rule” after all, but it also doesn’t mean you should be overly concerned about dropped food. Dawson concluded his study by saying that bacteria is kind of everywhere and, for better or for worse, we really can’t avoid it. The small chance that we’ll drop our food on the kind that will make us sick (that is, if we’re in a relatively clean place like our own home, rather than say, on the streets of New York City), is small, and most of us have pretty stellar immune systems.

That said, you can take your chances, regardless of seconds (or even minutes), or you can just fix yourself a new snack. Happy eating!

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