Is there any truth behind the “5 second rule” ?
First of all let’s get some facts straight. There is not a swarm of bacteria lying on the ground, waiting to pounce on any food that comes their way.
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.
“You can’t hide yourself from microorganisms. That’s the whole point. You are literally living and breathing a sea of bacteria,” says Gilbert.
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”.
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.
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.