Is the Five-Second Rule Any Good?

When people drop food on the floor, should they scoop it up quickly and eat it–or throw it away? In other words, does the five-second rule apply?

What’s the Five-Second Rule?

In this popular belief, if you get something off the floor quickly enough it won’t collect enough germs to pose a problem. It is often invoked in jest, especially if what you dropped is especially valued. But there has been a paucity of data to uphold or refute it.

Testing the Five-Second Rule:

A microbiologist has now tested the five-second rule and found that it doesn’t hold. He and a graduate student tested four different foods–watermelon, plain bread, buttered bread and gummy candy. The foods were dropped onto four different surfaces of carpet, wood, stainless steel and ceramic tile for four different amounts of time. That included less than a second, 5 seconds, 30 and 300 seconds. The surfaces had bacteria applied and allowed to dry completely before the food was dropped. With multiple tests of each condition, more than 2,000 samples were tested.

What Is the Riskiest Combination of Food and Surface?

Carpet transferred the least bacteria, while tile and stainless steel transferred the most. Watermelon picked up the most bacteria. The five-second rule does get at one truth: the longer food remains on the surface, the more bacteria it acquires. But even at less than one second, food becomes contaminated with bacteria and should not be popped in your mouth.

Applied and Environmental Microbiology, online 2 Sept. 2016