Researchers Disprove the Thought

The five-second rule is a belief that food that falls to the floor can be safely eaten as long as it’s picked up quickly. Researchers from Rutgers University, in New Brunswick, New Jersey, sought to test its veracity. Four different food items were tested, including watermelon, bread and butter, plain bread and gummy candy, using four different surfaces—stainless steel, ceramic tile, wood and carpet.

Each surface was contaminated by bacteria and completely dry before the scientists dropped each item for one second, five, 30 and 300 seconds. A total of 128 separate scenarios were repeated 20 times each and 2,560 measurements were taken and analyzed for contamination.

The results proved that longer contact time resulted in more bacterial contamination, but there were also cases of instantaneous contamination, which disproves the five-second rule. The wet surface of a watermelon yielded the most contamination and gummy candy the least. The surface tests yielded surprising results, with carpet transferring significantly fewer bacteria than tile and stainless steel, while wood floors exhibited varied results.