You most likely have heard of the five second rule: If your food fell on the floor, you have five seconds before the germs get on it. But how is it true?
Only two official scientific studies have researched this myth— and their findings are not that simple.
What is the 5 second rule?
According to National Geographic, the five second rule is a way people estimate “how quickly bacteria transfers from the surface of your floor to your food.”
Per Cleveland Clinic, your food will pick up bacteria when it falls to the ground. It’s just inevitable. The real concern is what type of bacteria you’re picking up and if it is strong enough to get you sick.
A survey in the early 2000s from the the University of Illinois showed that 70% of women knew about the five second rule, according to WebMD, whereas only 56% of men knew about it. The survey also found that women were more likely to practice the rule, yet a lot of people were likely to eat a candy or cookie that fell on the ground than vegetables like broccoli.
Two studies put this rule to the test, one in 2007 and another in 2016. The 2007 study found that the illness Salmonella Typhimurium can instantly transfer to foods that have fallen onto the ground.
The 2016 study found that certain types of food gathered more bacteria than others. These two studies also found what types of food and surfaces spread more bacteria.
What surfaces and food types are more likely to get germs on them?
The 2016 study found that the amount of bacteria transferred from a surface to food depends on a variety of factors, such as surface type, food type and how long both were touching each other.
According to National Geographic, this study found that wet foods, such as watermelon, picked up more bacteria than dry foods (like bread or gummy candy). It also found that carpets spread less germs than tile floors.
The 2016 study concluded that the level of moisture in a food impacts how much germs it picks up — with more moisture resulting in higher rates of transferred bacteria — and that the longer you left your food on a dirty surface the more bacteria you’re picking up.
Both the 2007 study and the 2016 study found that carpeted floors transferred less bacteria than tiled or wood floors.
There are other circumstances to consider. Cleveland Clinic shares how it’s safer to pick up and eat food from your own home floor than it is from a gas station floor. Paul Dawson, the food scientist that led the 2007 study, told National Geographic that “in most cases, eating a cookie that has picked up a little dust and floor bacteria is not likely to harm someone with a healthy immune system.”