What do these numbers tell us about the five-second rule? Quick retrieval does mean fewer bacteria, but it’s no guarantee of safety. True, Jillian Clarke found that the number of bacteria on the floor at the University of Illinois was so low it couldn’t be measured, and the Clemson researchers resorted to extremely high contamination levels for their tests. But even if a floor — or a countertop, or wrapper — carried only a thousandth the number of bacteria applied by the researchers, the piece of food would be likely to pick up several bacteria.
Of course we can never know for sure how many harmful microbes there are on any surface. But we know enough now to formulate the five-second rule, version 2.0: If you drop a piece of food, pick it up quickly, take five seconds to recall that just a few bacteria can make you sick, then take a few more to think about where you dropped it and whether or not it’s worth eating.