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That five-second rule we all live by is a myth, according to science

Adriana Velez is Food Editor for SheKnows. She spent her formative years in Brooklyn, which pretty much explains everything about her. She now lives somewhere else and has discovered life after kale and kombucha. She's written for Civil ...

What you should know about your food once it's hit the floor

Ah, the five-second rule of dropped food — we've all relied on it from time to time, haven't we? Unless you're an uncompromising germaphobe, we've all reached down and grabbed a piece of fallen food. And we tell ourselves that as long as it doesn't linger there too long, it's not too bad. We engage in this magical thinking that we can move faster than germs can.

More: Tips to avoid contaminated fruit, vegetables and meat

I think you know what's coming. Yes, just as we feared, we are losing that race with germs. Scientists at Rutgers University tested it out, and it turns out your fallen food picks up bacteria from the floor faster than five seconds. By the time you've bent down and plucked that french fry from the ground, it's already picked up a few bacterial hitchhikers. And they're going into your month.

Don't be too grossed out, though. It's not as bad as you think, either.

The researchers tested four foods: dry bread, buttered bread, gummy candy and watermelon. And they tested four surfaces: stainless steel, tile, wood and carpet. And they tested these foods dropping to these surfaces and staying for less than a second, five seconds, 30 seconds and 300 seconds. Here's what they found.

  • Watermelon picks up the most bacteria, while gummy candy picks up the least. Moisture matters. Moist food attracts more bacteria than dry food. You hate that word even more now, don't you? Moist.
  • Anyway, food picks up the fewest bacteria from carpet. Wood is funny, though — how much bacteria it transfers depends a lot on the texture of the surface.
  • Time does matter. Food picks up more bacteria the longer it stays. But the surface texture and the moisture of the food matter far more than the time spent on the floor.

More: How long can I leave out my barbecue food before I get food poisoning?

I would think a whole lot of other factors matter as well. For example, if you dropped the food on your kitchen floor, do you wear shoes inside the house? If you do, there's probably a lot more bacteria there than if you pad around in house slippers.

That said, here's the thing we forget when we talk about eating bacteria-ridden food. Our bodies do a great job of protecting us from the harmful effects of that bacteria. As Mary Roach, author of Gulp (a book about your digestive system) points out, we carry a powerful germ-killer right in our mouths.

As a germ killer itself, saliva has few rivals. Its anti-clumping properties keep bacteria from forming colonies on the teeth and gums. And it contains histatins, which not only kill bacteria, but have been shown to speed wound closure independent of antibacterial action.

So keep that in mind the next time you drop a piece of buttered toast on the floor. Yes, you've just picked up some extra bacteria. But if you have a healthy immune system and you eat any, you'll probably be all right. Of course, many of us already know this from experience.

Still, when I dropped two bowls of bibimbap on the floor the other day (complete with perfectly poached eggs, and yes my heart broke with the yolks) I think we did the right thing in cleaning it all up and throwing it all way.

More: The gross thing people do with food that we all pretend doesn't happen

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