Mythbusting the 5-Second Rule

The other day after school, my son was eating an orange in the kitchen. As I was leaning against our counter talking to him about his day, I witnessed him dropping a piece of his orange on the floor. In an instant he yelled, “Five-second rule!”

I watched him pick up the orange in one second flat and pop it into his mouth, which was followed by a huge smile of satisfaction. I had taught him not to eat off the floor, of course, but he was very intent on eating that orange.

So after watching my son stuff a likely disease-ridden piece of fruit into his mouth, I wondered—is the 5-second rule scientifically accurate? It turns out that there were actual studies done to test this.

High School senior Jillian Clarke used her six-week internship in the Department of Food Science and Human Nutrition at the University of Illinois at Urbana-Champaign to figure it out. Meredith Agle, a doctoral candidate at the time, questioned the results at first.

“Jillian swabbed the floors around the University in the lab, hall, dormitory, and cafeteria to see how many organisms we could isolate,” Agle tells WebMD. “We examined the swabs, and there were very few microorganisms. That surprised me. I told her to do it again.”

The results were the same. Agle, who earned her doctoral degree and is currently a scientist in new product development for Rich Foods in Buffalo, NY, had an explanation. “I think the floors were so clean, from a microbiological point of view, because floors are dry, and most pathogens like salmonella, listeria, or E. coli can’t survive without moisture.”

To control the study, Agle and Clarke placed cookies and gummi bears on tiles which contained measured amounts of E. coli. In this case, Agle reported, “We did see a transfer of germs before five seconds. We were dealing with a large number of cells.”

The study did not include carpet or damp floors, and did not involve gum or ice cream, also common in these situations. In a further study, Clarke found that 70 percent of women and 56 percent of men were familiar with the rule—and shock of all shocks—women were more likely to invoke it! These studies earned Clarke an Ig Nobel prize in 2004 at Harvard University.

Nevertheless, two experts told WebMD that it is still a bad idea to eat food off the floor. Ruth Frechman, MA, RD, spokeswoman for the American Dietetic Association, encouraged washing food before you eat it. “Bacteria are all over the place, and 10 types, including E. coli, cause foodborne illnesses, such as fever, diarrhea, and flu-like symptoms.” Symptoms can take a while to emerge, she noted.

Even if Clarke’s study did not debunk the “5-second rule,” it only takes 0.1 percent of certain types of bacteria to make you sick. Even if the odds are in your favor that you won’t get sick, it seems foolish to take a chance, seeing that some strains of bacteria can actually kill you.

There is also a “gross” factor to the “5-second rule”—there could easily be dirt and hair on it. Gag! No thanks, I’ll get a new, clean piece of food instead.

Have you tested the 5-second rule? Let us know by leaving a comment.