Debunking the myth behind the five second rule

Anyone who loves food knows the sinking feeling when something delicious falls on the floor. Staring woefully at a particularly buttery piece of toast or other mishandled treat is one of the more mortifying experiences for a food fan. So common is the accidental drop that we’ve had to come up with a number of ways to justify eating carpet food. Everything from a light brush to a quick rinse under the tap passes for many people, depending on the snack involved. However, for all our varied excuses for poor hygiene, there is one that has proved more persistent than all the rest. The five-second rule is now gospel in households everywhere.

The rule itself couldn’t be more self-explanatory. According to wishfully thinking clumsy foodies, any food that happens to fall to the floor is fine to retrieve and eat, provided it’s only been there for five seconds or less. This logic also applies to park benches, work surfaces, grass, or really anywhere where food could fall.

Providing the drop hasn’t attracted too many bits of unwanted detritus, diners are allowed to declare to the room that the five second rule has been enacted and snaffle the errant tidbit – usually without first returning it to the plate. At this point, everyone will solemnly nod before returning to their own food. The only hard and fast rule is that the five second timeline never be exceeded, lest the diner catch some ungodly disease from the floor. After all, no food is more important than health and safety.

So ubiquitous has the rule become that it is adhered to all over the world. It features in films, books and sitcoms and is an absolute necessity for careless eaters everywhere. Most students would starve were it not for the forgiving nature of the five second rule.

But unfortunately for everyone, one group of people is determined to stop the rest of us blissfully scabbing off carpets and kitchen tiles. Scientists, seemingly set on ruining everyone’s fun, have announced that our faith in speedy floor scrounging is entirely misplaced.

The battle between science and the five second rule has been raging for decades. In 2016, a team from Rutgers University delved deep into the circumstances of a standard food drop to understand how contamination could take place. The team, led by Drs Robyn C. Miranda and Donald W. Schaffner, tested over 120 different drop scenarios – possibly the most comprehensive look at the five second rule ever undertaken. Their findings were a blow to every self-respecting scavenger.

Toast on floor

According to Schaffner, any food that comes into contact with a surface for even a second will become contaminated. During the study, the team tested foods as diverse as watermelon, toast, gummy bears and buttered bread on four different surfaces – stainless steel, ceramic tile, wood and carpet. Each surface was then slathered in samples of a harmless relative of e coli, before segments of the food were dropped from a height of five inches. The segments were left for periods of one second, five seconds, 30 seconds and 300 seconds. Though samples in the longer periods were unsurprisingly more greatly affected, the food became contaminated in every instance. The test had proved that time was no obstacle to bacteria. The five second rule was a farce.

On the face of it, it might seem that the science delivers a pretty damning indictment of five second-based logic. Yet all hope is not lost for the dyspraxic diner. The Rutgers study also revealed that, though all test foods did become contaminated, some types were worse off than others. Since the cells don’t have any legs, bacteria typically moves by transferring through a liquid, meaning that wet foods, such as buttered toast or a sweet that’s slipped out of someone’s mouth, will attract more bacteria than something dry. Anyone still willing to risk a foray into floor food can therefore avoid soggy snacks and instead stick to liquid-less alternatives.

Despite the revelations unearthed by the Rutger’s team, it’s important to note that this was not the first time that science had attempted to seriously tackle the five second issue. In 2003, then-high-school student Jillian Clarke decided to submit her own study that also concluded that stickiness or wetness was the key factor that ultimately governed contamination. However, in a further boost to five second zealots, Clarke also concluded that most flooring is typically free from significant levels of harmful bacteria, so any food eaten quickly is still unlikely to do significant damage. Clarke was awarded the 2004 Ignobel Prize for her efforts.

If the interventions of scientists prove anything it’s that, though it might be mostly meaningless, sticking to the five second rule is unlikely to kill you. Anyone desperate to keep sticking to the arbitrary deadline should therefore feel relatively relaxed. Deep down, we all already knew that eating anything off the floor was probably a bad idea. Unfortunately, food is sometimes too delicious to just give up.