The five-second rule has become quite popular as well as an accepted norm in our daily lives. But is it actually true? Do bacteria really take more than five seconds to be transferred onto our dropped food? Surprisingly, there have been quite a few studies on this phenomena, and they have all mostly come to the conclusion that the five-second rule is not applicable in every scenario.
There is no debate on the fact that the longer the food is left on the ground, the more bacteria is transferred onto it. However, research shows that the rate at which bacteria is transferred is not uniform. The texture of both the foods and the surface that it has fallen on has an important role in determining the amount of bacteria that is being transferred.
A recent study conducted in 2016 itself took samples of different types of foods and surfaces and measured the amount of bacteria transferred over different time intervals. The study was conducted at Rutgers University and involved a data set of 2,560 measurements showing that the study’s conclusion can be trustworthy assuming that the experiment was carried out fairly. Unlike other studies, there were several X-Variables in the experiment. The researchers were manipulating the surface by interchanging between stainless steel, ceramic tile, wood and carpet, the food by interchanging between watermelon, bread, bread and butter, and gummy candy and the time by interchanging contact time from less than a second, five seconds, 30 seconds and 300 seconds. The bacteria used in the experiment were ones that occurred naturally in the human digestive system. The mixture of the variety of the types of surface, food and contact time lead to 128 possibilities. Each one was carried out 20 times. To minimize the effect of third confounding variables, the surfaces were allowed to dry completely before coming in contact with the food. All in all, the well-controlled environment and frequency of the number of times the experiment was conducted show that the researchers conducted a fair study.
The head researcher, Donald Schaffner explained the results of the study and identified a possible mechanism. He concluded that the food was contaminated at different rates and that all the causative variables along with factors like moisture were the reasons behind it. For example, the study showed that wetter foods experienced more contamination in comparison to dryer foods. The study also showed that the foods began being contaminated as soon as the food got in contact with the surface.
In conclusion, while the five-second rule may seem plausible in showing that the longer the food stays in contact with the surface the more contaminated it gets, it tends to ignore the fact that contamination starts as soon as contact is made. So the next time you hear the five-second rule being used make sure to look at the texture of the food and the surface it touches. You may just be satisfying your hunger with bacteria rather than food.
Rutgers University. “Researchers debunk ‘five-second rule’: Eating food off the floor isn’t safe: Sometimes bacteria transfer in less than a second.” ScienceDaily. ScienceDaily, 9 September 2016.
Aston University. “Dropped your toast? Five-second food rule exists, new research suggests.” ScienceDaily. ScienceDaily, 10 March 2014.