They say do one thing every day that scares you, but ideally that thing should not involve putting dubiously contaminated pieces of food in your mouth. As we grew up, many of us adopted the behavioral trait of shouting “Five second rule!” when we snatched an escape sausage from the floor, but is there any truth in the fact that there is a time limit on pathogen accumulation?
As children, we are taught that bacteria are everywhere, and over time (or in the face of a deadly global pandemic) we pick up the names of some of the usual suspects. Early estimates put the durability of SARS-CoV-2 on surfaces in about three days. It is a large window for sausage loss and pickup.
Surface bacteria are a big problem in places like gyms, where many people voluntarily put their bare skin to sweaty benches and mats: environments where Staphylococcus bacteria thrive. This particular group of germs like to get right up into your skin and cause exuding lesions that are highly contagious.
Five-second rule: How does time affect pollution?
So how would a sausage fare when you roll across your kitchen floor? Does time affect the ability of objects to detect pathogens? Is a sausage picked up on a five-second flat safer to eat than one that has lingered for five minutes crawling on the skin?
“There has actually been some research into how much bacteria can be transferred to food within five seconds,” said infectious disease specialist at Addenbrooke’s Hospital, UK, Dr. Dominic Sparkes to IFLScience. “However, it depends a bit on the surface.
“On tiled surfaces, as much as 99 percent of the bacteria were transferred to the piece of food (in this study a piece of bologna). So your five seconds are probably ample time to transfer potentially pathogenic bacteria to your food, in fact all time on the floor is likely too long.”
Bad news, then, for the lost sausage drops. But is a little bit of bacteria not okay now and then?
“While true, it is unlikely that most bacteria cause gastrointestinal disease, there are some – for example salmonella – that not only cause gastroenteritis but can also survive for long periods on surfaces. Even small amounts of these bacteria can make you uncomfortable.
“There are other bacteria that are often found in the environment and that produce toxins. For example, Bacillus cereus. When ingested, these toxins cause vomiting, and your food is much more likely to trap these organisms if it rolls across your kitchen floor. Work surfaces are generally thoroughly cleaned, which kills these bacteria. However, most kitchen floors in the home are rarely cleaned so thoroughly, and therefore the risk of your food absorbing disease-causing organisms is much higher on the floor than your kitchen worktop. “
* carefully places the fallen sausage in the rubbish bin *
Five second rule: Where did it come from?
Like many other speeches, the exact origin of the five-second rule is unclear. According to a report by the Huffington Post, the food security approach has ties as far back as Genghis Khan – the first major khan in the Mongol Empire, whose reign began in 1206.
Allegedly, the infamous manager had a “if it’s good enough for me, it’s good enough for you” rule about eating fallen food. Not so oppressive at the five-second mark, but a bit authoritarian, it’s a four-hour matured pool of floor yogurt.
Whether the five-second rule seeped down from the grubby kitchen floors of the Mongol Empire to the present is not clear, and it is unlikely we will ever know for sure. One thing that seems certain, though, is that there is no scientific backing for your food suddenly changing from seconds five to six. Not that it necessarily stops many of us.
“Of course, it’s totally against my actual practice, which is to eat what I find on the floor, no matter how long it’s been there,” Sparkes concluded.