Does the ‘5-second rule’ really work to keep off germs?

You know that old adage that says food dropped on the floor can be eaten if it’s picked up within five seconds? A new finding suggests there may be some validity to that claim, but I’m not putting much stock in it.

A microbiologist at Great Britain’s Aston University and his biology students decided to test how quickly common bacteria glommed onto food dropped for 3 to 30 seconds on various types of surfaces such as carpet, laminate, and ceramic tiles.

They found that the amount of E. coli and staph bacteria transferred depended on time, type of floor, and the moistness of the food. Bacteria were least likely to transfer from carpeted surfaces onto dry foods and most likely to transfer from laminate or tiled surfaces to moist foods — sticky buns rather than dry biscuits — that made contact for more than five seconds.


“Consuming food dropped on the floor still carries an infection risk as it very much depends on which bacteria are present on the floor at the time,’’ study author Anthony Hilton said in a statement. “However the findings of this study will bring some light relief to those who have been employing the five-second rule for years, despite a general consensus that it is purely a myth.’’

(He and his students did an informal survey and found that 87 percent of respondents said they would eat food dropped on the floor, or already have done so, and more than half the women who did so said they followed the five-second rule.)

I wouldn’t conclude that this new research meets the burden of “proof’’ that the rule can safely be followed. The study hasn’t yet been published in a peer-reviewed journal, so we don’t know for certain whether the results and methodology were valid.

What’s more, previous research that has been published suggests that bacteria break the rule all the time. A 2007 study from Clemson University found that Salmonella bacteria was transferred from table tops and floors to a piece of bologna almost immediately on contact and that the five-second rule doesn’t apply. They also found that Salmonella can live on surfaces for up to four weeks.


Carpeted surfaces were the least likely to transfer bacteria in both the new and previous research, so if you must eat that cookie or French fry off the floor, make sure it’s carpeted.

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November 16, 2017 | 5:19 AM