Supposedly dropped food is safe for about five seconds. Is there any truth to this supposed "rule"?
BBC By Melissa Hogenboom 23 March 2016
I dropped a piece of chocolate the other day, and briefly wondered just how many bacteria I had added to my tasty treat. But I saw no dirt, so went ahead and popped the chocolate into my mouth.
After all, my kitchen floor is pretty clean and the chocolate had been on the ground for less than five seconds.
The "five second rule" was therefore in my favour, obviously. We all know that rule, right? Any food picked up from the floor is perfectly fine to eat within five seconds of dropping it.
But was I right to eat it, or had I unwittingly stuffed my mouth full of tiny, harmful microbes?
We asked you, our trusty BBC Earth community, what you would do in a similar situation.
Seems a shame to waste it (Credit: Stocksolutions/Alamy Stock Photo)
The rule must be true, says Adam Harmsworth. "Surely all bacteria and infectious organisms understand the concept of time," he says.
Wishful thinking Adam. Gary Burch says that he goes by a three-second rule but for another reason entirely. "That's the average time from when I drop food on the floor until the dog has finished eating it."
Manuel Rodriguez says that he is a poor grad student, so he follows the five-minute rule. But others are far stricter. Corinne Howard says: "If it doesn't go straight to mouth it goes in the bin."
"We're talking about microseconds for bacteria to reach your just-dropped food," says Jon Bedet. "A zero-second rule would make more sense."
It "depends on the food and how hungry you are," says Lane Jasper.
To settle the debate, I put the question to scientists who specialise in microbes. Would they eat dropped toast, or pizza, or for that matter, dropped sticky toffee?
Instead, they are already everywhere, even if you have just mopped the floor. Adam Taylor helpfully points out: "Scientifically speaking there is no five-second rule. If the food touches surface for nanosecond it is contaminated."
As soon as any food touches the floor, "of course it will pick up 'dirt'", and therefore microbes inside that dirt, says Jack Gilbert, a microbial ecologist at the University of Chicago in Illinois, US.
At any one time, there are about 9,000 different species of microscopic creatures lurking in the dust in our homes, including 7,000 different bacteria, according to a 2015 study. Most of them are harmless.
They are all over you all the time; on your hands and face, and in your house. We are constantly shedding bacteria through our skin and through the air we breathe.
Researchers have even put a figure on it. Each person emits about 38 million bacterial cells into their environment each hour, a study found.
And yet, says Gilbert, we have been told for over 100 years that microorganisms are dangerous and "we need to kill them all".
"We are so paranoid about dirt and yet we have no comprehension of the pure luck – or bad luck – that it takes to actually pick up a pathogen," he says.
Gilbert would certainly eat food that he drops, provided the environment was reasonably safe. "If I dropped it into a plague pit, no, I wouldn't pick it up," he clarifies.
In fact, he goes further. Most of the time, even licking your floor or your toilet seat is unlikely to make you sick.
There are certainly some harmful pathogens around. But if one is lurking on your floor, it could also be elsewhere in your house, perhaps on your kitchen counter or door handle. You could become ill regardless of whether you ate food from the floor.
The usual warnings apply. If you are unlucky enough to host Salmonella bacteria on your floor, dropped food could make you sick even if it was on the ground for five seconds or less.
One 2006 study found that there was less risk of exposure of Salmonella in five seconds than one minute, but the risk was still there.
There is no magical barrier between yourself and the bacterial world, so even the strictest cleanliness will not keep them out.
In fact, contact with the microbial world can benefit us.
"Unless you are dropping food in a doctor's office or in a portable toilet, exposure to microbes is good," says Katherine Amato of Northwestern University in Illinois, US.
That is because we have evolved with microbes all around us. Researchers like Amato increasingly believe that they have played a significant role in the evolution of our species.
We pick up microbes from our environment when we are very young, including from contact with dirt. A child's "microbial community" starts to look like an adult's at around the age of two.
"If there are microbes on that piece of food it could [therefore] contribute to the development of the healthy immune system," says Amato. "I say go ahead and eat it."
"You don't build an immune system by being a germophobe," agrees Natalie Henning.
In other words, the five-second rule is nonsense. If there really is a nasty microbe about, sticking to the rule is not going to prevent you from getting sick. And the rest of the time, it is fine to eat food from the floor.
I'm not sure I want to try licking toilet seats, though.
Melissa Hogenboom is BBC Earth's feature writer. She is @melissasuzanneh on Twitter.
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I'm good with the 5-second rule most of the time - at least in my own home. I don't get sick much, and I've never gotten sick from eating something I dropped on the floor. I have a cat and a dog. My place is probably an epic bacteriological amusement park. When the jar of spaghetti sauce in the fridge grows a little mat of fuzz, I pick it off and eat the sauce anyway. I mean, I've got a pot sitting on the stove with pasta cooking in it. Do you think I'm going to go charging down to the store to buy more Ragu? Heck no! Oh yeah, I know - the fuzz on the top of the sauce is just the tip of the iceberg. There's invisible tendrils stretching down into the tomato-y depths of the jar. So what?
I'm the person who trades licks on an ice-cream cone with my dog. My cat sits on my pillow, for Pete's sake. And mushrooms are grown in cow shit. Oh sure, you can wash 'em, but you know what's lurking between all those little gills on the bottom side of the 'shroom? Yup, you got it.
Relax... Most germs are harmless. Maybe even good for you. Paranoia, on the other hand, can scramble your brains.
The Buttered Cat Paradoxfrom: MentalFloss
Some things we all know are true appear to contradict each other, and even though we are aware of the facts, we cannot always know what will happen when these concepts come together. One such concept is that of the buttered cat. In most cases of scientific conundrums, experiments are used to find the answer. When there is a cat involved, getting the required cooperation from the test subject makes this all but impossible. But I'm getting ahead of myself. First, let's understand the paradox of the buttered cat.
We all know that if you drop a piece of buttered toast, it will land on the floor butter-side-down. Common knowledge? Sure, but Rob Cockerham tested that adage with a series of experiments. He found that it doesn't always happen. In his trials, anywhere between 5% and 20% of the toast landed butter (or jelly) side up! Still, those are disappointing odds. Some say that the buttered side faces downward because that side is heavier, you know, because it has butter on it. Jelly has the same effect.
In the same vein, we know that a cat, when dropped, always lands on its feet. Or does it? The existing literature says that cats need some time to orient themselves in space, and cannot land on their feet when dropped from a height less than 1.5 to 2 feet. This is especially true if the cat is asleep. The side effect of such research is often a very annoyed cat.
So we can say that dropped toast almost always lands butter side down, and dropped cats always land on their feet under under most conditions. But in 1993, artist and quantum thinker John Frazee posed the question in OMNI magazine about what would happen if you were to attach toast to a cat's back -butter side out, of course. One reader said that you could go ahead and skip the toast, since it is the butter that is attracted to carpet. Chicken tikka masala would work even better, if you were dropping the cat on a white carpet. I'm not sure that changing the parameters would aid in solving this paradox. Most researchers tend to stick with toast, although some use butter and others use jelly.
What would happen in such a scenario? Both the butter on the toast and the cat's feet would be attracted to the floor -or possibly the opposite side of both objects would be repelled by the floor. This conundrum became known as the Buttered Cat Paradox.
Those who have tackled the problem as a thought experiment (meaning, no cats were harmed) have come to the conclusion that the buttered cat would stop falling at some point above the floor. Then, as the cat tries to orient its feet against the attraction of the butter to the floor, the cat would begin spinning -and never stop. The result could be called a true perpetual motion machine.
How could we harness this amazing power? The first thought, proposed by Frazee back in 1993, is that many "anti-gravity cats" could be used to power a monorail system.
It has been posited that extraterrestrials use this power to drive UFOs. The humming of the spacecraft is attributed to many cats purring as they spin. The theories and mechanics of such a perpetual motion energy system are explored in breathtaking detail at Uncyclopedia. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|And remember - if you have one of those weird toasters that makes the face of Jesus appear on your toast; butter it on the other side - just to be on the "safe side." Yes, there are such things, and you can buy one on Amazon.|