Is There Any Truth to the "Five-Second Rule”?

Rutgers University researchers aren't klutzes, but they did drop an awful lot of food on the floor recently -- all in the name of science.

It could take far less than five seconds for these strawberries to become contaminated.
It could take far less than five seconds for these strawberries to become contaminated.

Their objective was to test the accuracy of the so-called "five-second rule," which states that food is safe to eat if you grab it off the floor within five seconds of having dropped it. The researchers played fumble fingers with pieces of watermelon, gummy candy, and buttered and non-buttered bread, dropping the food items onto an assortment of surfaces and leaving them there for various lengths of time.

They then tested each piece of food for bacteria. In all, the team evaluated 2,560 such scenarios and found that the five-second rule doesn't fly. The moisture in a food item makes it more susceptible to contamination, and some surfaces provide much better host environments for bacteria than others. In some cases, such as dropping watermelon on a stainless steel surface, the contamination is immediate.

One of the researchers, Prof. Donald Schaffner, an extension specialist in food science, said the bottom line is simply that you can't expect dropped food to be safe, no matter how quickly you grab it. "The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food," he said.

The facts on food safety:

  • Contaminated food causes the deaths of approximately 420,000 people every year, including about 125,000 children.

  • Leftover food should be placed in safe containers and refrigerated immediately, as bacteria can grow even at room temperature.

  • Up to 3 percent of secondary long-term illnesses like meningitis and arthritis are caused by food poisoning.

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