Not a single child in the United States isn’t well-versed in the five-second rule and hasn’t at some point taken advantage of it not to waste their favorite piece of candy. Unfortunately, this famous “rule” may not be as true as many would hope.
According to The Irish News, basic level experts say that even before five seconds is up, you shouldn’t eat anything dropped on the floor because bacteria can transfer to food instantly. In fact, bacteria can live after four weeks just on a carpet, and thanks to a process called “microbial adhesion,” germs such as Salmonella typhimurium, Campylobacter, and Salmonella enteritis, which cause horrible diarrhea and vomiting, can transfer immediately to food.
One of the first official studies testing Genghis Khan’s theory of bacterial contamination — even though he believed food could be safe for consumption even after 12 hours on the floor — was conducted by American high school student Jillian Clarkes as part of an apprenticeship at the University of Illinois.
By inoculating smooth and rough tiles with E. coli, Clark placed either cookies or gummy bears on each tile for five seconds or less. She found that bacteria did transfer to the foods, and that gummy bears were far more susceptible to the transmission.
Similar results were found in a separate study by researchers in the Journal of Applied Microbiology. They contaminated wood, tile, and carpeted surfaces with Salmonella, and then dropped bread on them for either five, 30, or 60 seconds.
Their findings insinuated that the time spent on the floor didn’t affect how much bacteria accumulated on the food, but the type of surface did. Hard surfaces, such as tile or wood, transferred up to 5 to 68% of bacteria, while food dropped on carpet picked up less than 0.5%.
However, The Irish News and The Royal Gazette alike reported on a study from Aston University, which claims that the time food spends on the floor is a significant factor in the transfer of bacteria.
The researchers monitored the transmission of E. coli and Staphylococcus aureus from carpeted, laminated, and tiled floor with different foods, including toast, pasta, cookies, and sticky sweets. They determined that food that came in contact with the floor for just three seconds had substantially less bacteria than those with 30 seconds of exposure, and the foods that made contact with tile after five seconds had transferred more than 99% of the bacteria.
“Salmonella Typhimurium can survive for up to four weeks on dry surfaces in high enough populations to be transferred to foods and… and can be transferred to the foods tested almost immediately on contact,” concluded the researchers.
The Royal Gazette also reported on a study by Clemson University in South Carolina that states the cleanliness of a floor is a more important consideration than the time food spends on the floor. After dropping bread and bologna on different surfaces, they found that on carpet treated with salmonella, less than 1% of bacteria transferred to food, as compared to 70% on wood and tile.
Regardless of which study had the most accurate findings, the fact of the matter is that any bacteria on the floor will transfer to food. Therefore, it’s time to throw out the five-second rule — and anything that falls off your plate!