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Five-Second Rule holds up in scientific research

We’ve all been that person who loudly exclaims “Five-second rule!” while scooping up a titbit of fallen food.

ice cream on the floor Five-second rule! Or, in this case, perhaps not.
Credit: Getty Images

We’ve all been that person who loudly exclaims “Five-second rule!” while scooping up a bit of fallen food. Anthony Hilton, a professor of microbiology at Aston University in Birmingham, England, discovered that there is a crumb of truth in the urban myth that food is still good to eat even if it has been dropped on the floor for fewer than six seconds.

His experiment, conducted by his students, also found that 87 percent of us would eat food that had fallen on the floor and, perhaps surprisingly, 55 percent of the worst offenders are women. The expert takes Metro through the science behind our filthy floor habits.

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Prior to this research, did you believe in the five-second rule?

I was skeptical because the idea that you could influence something after the event seemed unlikely. I assumed that the initial impact is when bacteria is transferred from floor to food.

Did the amount of time that food remained on the floor make any difference?

Surprisingly, it made a difference for moist (cooked pasta and sticky candy sweets) but not dry foods (biscuits and toast). Wet foods will pick up more bacteria on tiled and laminated floors, but this isn’t the case for carpets.

So are we safe to eat food off the floor in our homes?

The levels of bacteria present on the same surfaces in a home are very low in real terms. The ones that we found are normal skin microorganisms that accumulate indoors and none that would make you unwell.

Why is it bad to leave food on the floor for longer than five seconds?

The longer you leave food there, the more likely that bacteria is going to get on it. It’s not because organisms are mobile and attracted to the food; it’s actually because as the food hits the floor it presents a certain footprint, and the organisms are transferred within that contact patch. Over time, the product oozes more onto the floor and creates additional contact points.

Does blowing on food help remove bacteria at all?

I think that blowing isn’t going to lower levels of bacteria because the organisms are going to be intimately stuck on the food. If spit comes out, it could actually contribute to it, rather than reducing it. There is a caveat: We’re not advocating that people pick up floor food willy-nilly. What we’re saying is, if you happened to drop a crisp or piece of toast on a floor where normal hygiene rules apply — the floor is [vacuumed] once a week or mopped every few days — then you can with confidence assume that you’ll be fine.

Are mothers right when they advocate that a bit of dirt will do our immune systems good?

That’s from the hygiene hypothesis that states that a peck of dirt will do you good. People are confusing normal exposure with microorganisms and hygiene. There’s no evidence that not washing your hands after the loo or not cooking food properly will make you immunologically stronger. It will almost certainly make you unwell.

 
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