Health Debunked: Is There Any Merit to the 5-Second Rule?
Key takeaways:
The 5-second rule refers to eating food that has dropped on the floor as long as you pick it up within 5 seconds.
The theory was debunked by researchers when they found that the transfer of bacteria onto dropped food can happen in less than 1 second.
It’s better to toss food that has fallen on the floor rather than eat it.
Have you ever been faced with the split-second decision about what to do when the food you’re eating falls to the floor? You could pick it up and eat it or throw it out. Likely, someone will yell out “5-second rule!” as a reason to enjoy the dropped food. But should you listen? Find out why it may not be safe to eat food you’ve picked up off the floor, even if it’s within 5 seconds of dropping it.
What is the 5-second rule?
When food drops on the floor, people believe they can still safely eat it as long as they pick it up within 5 seconds. The idea is that bacteria from the floor will only stick to the food after 5 seconds but won’t stick right away. It’s been put to the test by scientists, and it turns out that the 5-second rule is mostly fiction.
Where did the idea come from?
The 5-second rule likely dates back sometime between 1162-1227 when Genghis Khan ruled the Mongol empire. When hosting parties and banquets, Khan established the “Khan Rule.” The rule said that any food prepared for Khan was so special that it should be eaten even if it had fallen on the floor. The rule was based on ego rather than science, but his guests followed it.
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Interestingly, famed chef Julia Child shared a variation of the 5-second rule in an episode of “The French Chef” in 1963. After Child flipped a pancake and it dropped onto the stovetop, she said, “You can always pick it up if you’re alone in the kitchen. Who is going to see?” Apparently, the pancake sat on the stovetop for about 4 seconds. Since Child figured it was safe to eat, her many loyal viewers followed suit and adopted the rule too. But how safe is it really?
Claim: You can eat food off the ground within 5 seconds
Some people exclaim “5-second rule!” when they drop food on the floor, then proceed to eat the food. The truth is, it’s not a good idea to eat food off the floor, since bacteria, such as salmonella or E. coli, can stick to it in less than 5 seconds.
What does the science say?
The risk of illness depends on the concentration and type of bacteria on the floor, the moisture of the food, and the surface of the floor.
In 2003, researchers at the University of Illinois tested the 5-second rule but never published their findings in a traditional journal. Instead, they wrote about it on the school’s website. The researchers found that if you drop your food on a floor that contains microorganisms, the food can be contaminated in 5 seconds or less.
In 2016, researchers at Rutgers University studied the 5-second rule and published the research. The researchers found that bacteria can stick to dropped food in less than 1 second, clearly disproving the 5-second rule.
The Rutgers researchers tested four different foods on four different surfaces and at four different time intervals:
Foods tested: Watermelon, bread, buttered bread, and gummy candy
Surfaces tested: Stainless steel, ceramic tile, wood, and carpet
Times tested: Less than 1 second, 5 seconds, 30 seconds, and 300 seconds
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The researchers found that watermelon had the most contamination, while the gummy candy had the least. They thought it was because moist foods have a higher risk of transferred bacteria.
They also found that the longer food is on the floor, the more bacteria can be transferred. So it is true that if food falls on the floor, leaving it for 5 seconds would be better than 30 seconds — but it doesn’t make 5 seconds safe.
As for surfaces, the researchers learned that foods dropped on carpet had the lowest number of bacteria, compared to tile, steel, and wood. They concluded that when it comes to bacteria, the type of food and the surface it fell onto is of equal or greater importance than the time it spent on the floor.
What do the experts say?
“Your floor carries dirt and pathogenic microorganisms you track into your home,” says dietitian Toby Amidor, MS, RD, CDN, FAND, award-winning nutrition expert and Wall Street Journal best-selling author of “The Family Immunity Cookbook.” “If you drop food onto the floor, you can get bacteria onto your food. One bacteria can double in number every 20 minutes. This means if you drop it on the floor and leave it out, then one bacterium can multiply to over 1 billion in about 10 hours, which can potentially make you sick.”
Amidor also explains that it's important to understand the difference between clean and sanitary.
“Your floor may be clean of visible dirt but can be unsanitary, meaning that bacteria and other harmful germs are living on it,” says Amidor. “Although you do use chemicals to sanitize your floor, certain pathogens like Norovirus can survive on surfaces for months.”
Amidor says you also can’t just use heat to destroy pathogens, since some can survive very cold and very hot temperatures. Or they may have grown to such high numbers that the heat can’t destroy them all.
The bottom line
Food that falls on the floor is easily contaminated with bacteria. And the risk may be higher for moist or wet foods. Not all bacteria on standard floors will cause illness, but why take the risk? People with developing or weakened immune systems need to be extra careful. That means young children, older adults, and people who have compromised immune systems should never follow the 5-second rule. Experts still agree: When in doubt, throw it out.
Why trust our experts?
References
Dawson, P. Sheldon, B. (2018). Did you just eat that?: two scientists explore double-dipping, the five-second rule, and other food myths in the lab.
Gibson, B., Wilson, D. J., Feil, E., & Eyre-Walker, A. (2018). The distribution of bacterial doubling times in the wild. Proceedings. Biological sciences.
Miranda RC, Schaffner DW. (2016). Longer contact times increase cross-contamination of enterobacter aerogenes from surfaces to food. Applied Environmental Microbiology.
University of Illinois Urbana-Champaign. (2003). If you drop it, should you eat it? Scientists weigh in on the 5-second rule.
