Dropped food is okay for five seconds: True/False?

I always knew it as the five second rule, Yvonne Beattie has heard three seconds, but either way she is concerned that people are risking their health based on a bit of wishful thinking. And she’s right.

I’m not sure whether anyone really believes that dropped food is perfectly fine as long as it doesn’t lie on the floor more than a few seconds. It sounds like one of those little lies we tell ourselves to justify something a bit naughty. Lots of evidence suggests that humans often make decisions first and rustle up a justification afterwards. It’s not surprising that the resulting reasoning is sometimes a bit wobbly — in the case of the five second rule the wheels have fallen off altogether.

I’ve never been sure how the five second rule is supposed to work. Do people think that bacteria are quite a lazy, slothful lot, who can’t rouse themselves to leap from the floor to your food without a slow start? Whatever the supposed mechanism, it’s all in the head. You don’t need the intimate knowledge of a microbiologist to understand bacteria in everyday life. As a rule of thumb there are very few places that they haven’t colonised and if they get an opportunity to colonise the rest they’ll jump at the chance. That includes your cheese and pickle sandwich, your slice of cake or whatever else you deposit on the ground.

As soon as you drop something on the floor it is contaminated. While the time on the floor can affect the degree of contamination somewhat, even brief contact leaves unhealthy levels of bacteria on the food. Perhaps surprisingly, smooth services like tiles transfer bacteria to food more easily than carpet — though because carpet hangs on to bacteria longer than other surfaces you end up with about the same contamination anyway.

Setting such woolly questions aside, though, once food hits the floor it is contaminated and if you think it is safe to eat you are deluding yourself. To paraphrase the late great Peter Brock: only a fool buys the five second rule.

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