Did you drop a piece of food on the floor and pick it up while touting the “five second rule”? As a dietitian, I’ve heard everything from the “five-second rule” to the “one-minute rule.” But is the food really safe to eat after it’s been on the floor for a while? Here’s what you need to know about the five-second rule.
For most people, “clean” means something is free of visible dirt. However, although your soil may appear to be clean, it may still contain a lot of invisible microorganisms. Most household floor cleaners kill most harmful germs for a while, but some bacteria and viruses (like norovirus) can still survive on surfaces for months. If you think you can “cook” by heating food before eating it, it’s important to know that some pathogens can survive both very cold and very hot temperatures.
There have been several studies examining the “five-second rule” revealing slightly different results. A 2014 study from the School of Life and Health Sciences at Aston University in Birmingham, England, indicates that the 5-second rule is in fact true. The study monitored the transfer of common bacteria Escherichia coli (E. coli) and Staphylococcus aureus from various types of indoor floors (carpets, laminates and tiled surfaces). He looked at toast, pasta, cookies, and sticky candy when he was in contact with the floor for three to 30 seconds. The results showed that weather and floor covering type were important factors in the transfer of bacteria from a floor surface to a piece of food. This study found that bacteria are less likely to transfer from a carpeted surface compared to a laminate or tiled surface when moist food comes into contact with it for more than five seconds.
So, does this study show that it’s okay to drop food for 5 seconds on the floor? Not exactly. Research has concluded that you are always at risk when eating food that has fallen on the floor because of bacteria that may be hiding there.
A 2016 study in the Journal of the American Society for Microbiology, Applied and environmental microbiology demystified the five-second rule. Researchers looked at what happens when you drop a variety of foods, including watermelon, bread, bread with butter, and gummies, onto four different surfaces. Surfaces included carpet, stainless steel, ceramic tile, and wood. Food was dropped and left on each surface for one second, five seconds, 30 seconds, and 300 seconds. Each possible scenario (a total of 128!) was repeated 20 times.
The results showed that the watermelon grew the most germs, even for a short time on the floor, and the gummies picked up the least contaminants. Bread and bread and butter were in the middle of germ levels. What the data revealed was that the longer food stayed on the floor, the more bacteria it picked up. However, even though the food only stayed on the floor for a few seconds, it was not bacteria-free, which contradicts the so-called five-second rule.
Even if you don’t always get sick from eating on the floor, it’s not the wisest decision. Very young and very old people have weaker immune systems and are more susceptible to disease, so it is especially important not to teach this habit to children. Yes, the sooner you pick up the food, the less likely it is to accumulate bacteria. However, it only takes one time to detect bad bacteria or too much bacteria that can make you sick.
*This article was written and/or reviewed by an independent dietitian nutritionist.