We’ve all dropped a cracker or slice of pizza on the floor and still wanted to eat it ― and maybe actually eaten it, while invoking the five-second rule. Is it okay to eat food that has been dropped on the floor? Are those five sacred seconds really enough to keep that pizza from being thrown on the ground? Or is this a fabrication we love to believe.
“Well, I actually don’t like to tell people what to do,” said Don SchaffnerRutgers University extension specialist, and distinguished professor in Rutgers University’s department of food science. “I like to tell people about the science and let them make their own decision. Certainly, if you drop something on the ground, it may contact germs, and if you eat those germs, they may make you sick.”
Whether the five-second rule ― or 10-second or three-second rule, whatever you call it ― is true is complex, experts said. The type of food and the floor, as well as what it is potentially contaminated, are all factors that affect this. Here’s why.
The five-second rule was created where?
No one is sure where the idea of the five-second rule originated, but it’s often attributed to 13th-century Mongolian ruler Genghis KhanAccording to legend, he had a rule that food that fell onto the ground would remain there for as long as it pleased him.
“There were some historical quotes from Genghis Khan about eating food off the floor in reference to a ‘if it was good enough for him, then it was safe for everybody’ kind of a response,” said Paul Dawson, professor at Clemson University’s food, nutrition, and packaging sciences department.
However, people of that era lacked knowledge about microorganisms and how they can cause illnesses, so eating foods off the floor may have been no big deal, according to the book “Did You Just Eat That?” Written by Brian Sheldon and Dawson.
Another reference to the myth comes from an inaccurate story about Julia Child, in which viewers reportedly remember her dropping a piece of meat and picking it up, saying that if you’re alone in the kitchen, no one will see if you drop foods. But according to Dawson, the story isn’t true.
“We couldn’t track down exactly when it started,” he said. “I think it’s just one of those society myths that kind of got started and people kept propagating it.”
What happens to food that has been dropped on the ground?
Dawson and Schaffner both studied the 5-second rule, and how different foods react to surfaces.
A 2006 study was published in The Journal of Applied MicrobiologyDawson, along with other researchers, looked into whether food contact time and bacteria transfer to food. They tested three floor types ― tile, wood and carpet ― contaminated with salmonella, and two kinds of food: bologna and bread.
According to the research, the flooring type and contamination levels were crucial. Carpet harbored more bacteria for longer but didn’t transfer as much to the foods; carpet’s porous surface enabled bacteria to seep in and not stand on the surface as much, Dawson said.
He explained that Bacteria can survive on surfaces without water for several weeks.
A study co-authored by Schaffner in 2016 was published in Applied and Environmental Microbiology JournalWe tested bread, watermelon and bread with butter, as well as gummy candies, that were dropped onto contaminated tile, carpet, and wood surfaces. The results showed that the time it took to drop on tile, wood, and carpet was less than one second.
According to research, the bacteria that was most likely to transfer to watermelon is the highest and the lowest to gummy candy. Although longer exposure is a significant factor in contamination, it can still happen even within a fractional of a second.
“Our research showed that in every single condition ― no matter what surface, what food or what time ― there were always some experimental trials where we saw some bacteria transfer,” Schaffner said. “There was no safe time where we never saw the bacterial transfer.”
Are there other factors that influence the five second rule?
While how long food is on the floor matters, the type of food and what’s actually on that floor matters just as much, if not more.
A food’s moisture level is a crucial factor, Schaffner said. In Schaffner’s study, for instance, they found that most bacteria was transferred to watermelon pieces dropped on surfaces.
“We think this is because the moisture facilitates movement of the bacteria from the surface to the food,” he explained. “Bacteria don’t have legs, so they really do require something like moisture to allow them to move.”
Drier foods like bread and gummy candy saw fewer bacteria transfer ― but they still picked up enough bacteria to make you sick, Dawson said.
The main issue is the level of contamination. Surfaces can sustain bacteria for many weeks. Any floor free from bacteria simply won’t transfer bacteria to food dropped on it.
“I would trust my freshly mopped kitchen floor more than I would trust another surface like a New York City subway platform,” Schaffner said.
Floors may also be covered with dust and pet hair that could cause bacteria to get onto your food. That’s not something you’d want to eat, but Dawson said it’s likely harmless in itself. However, bacteria can “ride on those particles,” he added.
Are the Five-second Rule’s five Seconds True?
“It’s pretty much a myth,” Dawson said. “It really depends on what’s on the ground and where the food lands.”
Food will pick up bacteria immediately, “so you’re just gambling if you eat it and you’re not sure what’s on that surface,” he explained. Foodborne illnessesFrom salmonella or other bacteria, it can cause nausea, vomiting and diarrhea. It can also be fatal.
“I worry about pathogenic bacteria and pathogenic viruses like norovirus that can cause illness,” Schaffner said, adding that the “five-second rule is not true.”
“There is no ‘safe’ amount of time when no bacterial will transfer,” he emphasized.