(According to the U.S. Food and Drug Administration, about 1-in-6 Americans contract a food-borne illness each year. In this blog, a professor from Clemson University explains why it is not wise gamble with your health based on a food safety myth.)

You’ve all heard it and many have practiced it; it’s the “5-Second Rule.”

oranges on gross looking carpet

You may want to re-think eating food you’ve picked up off the floor, even if you manage to pick it up within 5 seconds.
Image Credit: Carlos Harris

The recent pop culture interest in the 5-Second Rule included the MythBusters TV show and the Discovery Channel. The validity of this doctrine was a question studied by our group at Clemson University. We decided to conduct the study both out of curiosity and as a research-learning exercise in an undergraduate research program called “Creative Inquiry.”  As a result of this research we published the first refereed article on this topic.

To test the 5-second rule, we studied two factors: the duration of food contact with the contaminated surface, and the length of time that the surface had been contaminated with bacteria. We inoculated ceramic tile, laminated wood, and carpet with Salmonella Typhimurium.  The Salmonellae were allowed to remain on the surface for 15 seconds and 2, 4, 8, and 24 hours. We then placed bologna or bread on those surfaces for 5, 30, or 60 seconds. While the contact time had a statistically significant effect on bacterial transfer, there was, from a practical standpoint, a substantial amount of bacteria transferred to the food within 5 seconds, thus debunking the 5-Second Rule.

Chances are that eating food dropped on the floor will not make you sick. However, there is also a chance that it can; after all, there are more than 46 million cases of food-borne illnesses

in the United States each year. So, the next time you consider eating dropped food, remember this—if a microorganism capable of making you sick is sitting on the exact spot where the food dropped, you can be fairly sure you are about to put that microbe in your mouth.

Our Creative Inquiry research has and continues to test common food handling issues, publishing articles on double-dipping, blowing out birthday candles, handling restaurant menus, and sharing a bag of popcorn.

NIFA invests in and advances agricultural research, education, and extension and promotes transformative discoveries that solve societal challenges. The USDA supported the Creative Inquiry program at Clemson University, funding student research in the Food Science and Human Nutrition in 16 different topic areas.