Uh-oh. You dropped the last slice of pizza on the floor. Is it safe to eat if you swoop down and retrieve it fast enough?
Researchers at Rutgers University in New Jersey are here to tell you what you already knew deep down: the five-second rule is a lie. Bacteria can instantaneously contaminate food that falls on the floor.
The findings were published this month in the American Society for Microbiology's journal.
Researcher Donald Schaffner said the five-second rule is a “significant oversimplification of what actually happens when bacteria transfer from a surface to food.”
Schaffner's research isn't the first to disprove the homespun wisdom of the five-second rule.
An English microbiologist who dropped pieces of pizza, apple and buttered toast on a variety of E. coli-contaminated surfaces found that each sample was heavily contaminated, according to a 2015 post on the National Health Service website.
Studies done at the University of Illinois at Urbana-Champaign in the early 2000s found women were more likely to invoke the rule, with 70% saying they were aware of it. Only 56% of men said they'd heard of the rule. The type of food also was a factor: Dropped cookies and candy proved more likely to be eaten than broccoli and cauliflower that ended up on the floor.
The Rutgers researchers did find that longer contact time means more bacterial transfer, but that the type of food and surface are just as important, or even more so.
They tested watermelon, bread, bread and butter, and gummy candy on stainless steel, ceramic tile, wood and carpet.
Watermelon had the most contamination, they found, and that transfer of bacteria is affected most by moisture.