There really is no middle ground when it comes to the 5-second rule: Either you follow it, or you don’t. Some people have no problem picking up and eating dropped food as long as it’s within seconds of falling on the floor. Maybe they give it a hefty blow for good measure. But is it safe? The answer’s a little more complicated than a simple yes or no. Let's look at what the science says on the issue.
Would you believe researchers have conducted actual studies on the 5-second rule? What studies have found is that the type of food and type of floor makes a big difference when it comes to how much bacteria is being picked up. But there's a twist and it starts with your feet.
Just when you thought the amount of time really didn't matter: One study compared bacteria on dry Cheerios and wet noodles left on a typical kitchen floor for 5, 30 and 180 seconds. None of the dry Cheerios left for 5 seconds grew any bacteria, but researchers were able to culture one colony from the Cheerios left for 30 and two from the ones that had sat on the floor for 180 seconds.
All the wet noodles picked up bacteria, with nine cultures grown from one sample left for just 5 seconds. Every sample left for 30 seconds had multiple cultures, with the dirtiest growing a dozen different bacterial colonies. The worst noodle after 180 seconds grew twice that. Among the bacteria cultured were numerous strains of staph and strep along with a handful of potentially opportunistic bacteria that typically live in the soil.
A different study compared the volumes of bacteria picked up on different types of dry surfaces. The researchers found germs transferred more readily from wood and tile than from carpeting—a fact that surprised many. They also found some bacteria, such as Salmonella typhimurium, could survive on dry surfaces for about 4 weeks.
How clean are your floors? Do you disinfect them regularly? What measures do you take to keep them from becoming one massive petri dish? You might be surprised by how filthy they may be—especially if you allow people to wear shoes in the home.
If we wear shoes once we enter a home, we're tracking in all sorts of germs, and if that's not gross enough, most of those germs eventually make their way onto other surfaces. If you were to have your shoes swabbed right now, they’d likely test positive for E. coli and numerous other pathogens just from walking around in the world. Even if you don’t remember recently stepping in anything nasty, how can you be sure no one else who walks where you walk hasn’t? The floors in most public places are teeming with life, and it can spread easily.
So it seems like we should think about the surface, the type of food we've dropped, and seriously, five seconds is the max, people. But even so, the 5-second rule might not be reliable in most real-world scenarios. Though if you insist on using it, you can reduce your chances of contamination by keeping the surfaces in your home clean and your shoes left in the entry. Though given what we learned in researching this article, it's a safe bet we will decide not to take any risks, tossing any food that falls on the ground.
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