published Wednesday, March 9th, 2011

Forget the 5-second rule

Drop a piece of food on the floor at home, work, school or a public place and somebody who has witnessed the act is likely to holler, “5-second rule.” That unofficial but widely cited “rule’ says that is acceptable to eat the morsel if it was retrieved from its resting place in five seconds or less. No one is quite sure when or where the rule was promulgated, but it is now so venerable and so persistent that scientists have tested it. Their findings are instructive.

The five-second rule, researchers say, is more wishful thinking than fact, perhaps promulgated by some kid, a harried parent determined not to waste food, or someone inordinately proud of their housekeeping. None of that matters. Bacteria can attach to food as soon as it hits the floor. And since that bacteria can make people quite ill, it’s not worth the risk to consume it regardless of how quickly it was picked up.

Scientists at Clemson University tested the 5-second rule using bologna on wood, tile and carpeted floors. On the wood and tile floors, nearly 99 percent of the bacteria were transferred to the food almost immediately. Carpet transferred fewer bacteria, but there was no difference in the contact in time. In other words, bacteria are quicker than the hand.

Still, the rule has its adherents. Some argue that the floor, particularly in well-kept homes, is squeaky clean and unlikely to harbor dangerous germs. Not so. A floor might look clean to the naked eye, but microscopic examination almost always indicates the presence of bacteria, some of which can survive for long periods of time in difficult environments. Given that and the speed at which bacteria can attach to food, use of the 5-second rule poses a risk in most homes. It’s especially suspect in high-traffic areas like a school cafeteria or other public eating space.

There is, the scientists say, some truth to the belief that the faster food is retrieved from the floor, the less bacteria is likely to collect. That’s true, but hardly germane to the discussion of food safety since enough harmful bacteria to cause gastrointestinal distress can be transferred from floor to food in a second or even less.

So given the evidence, what’s to be done when food falls to the floor? No matter how tasty the dropped morsel might be, and no matter how quickly it is recovered, the operative rule, scientists and public health officials agree, should be “when in doubt, throw it out.”

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