Here’s a quick answer to that question: no, the 5-second rule is definitely not true. Even if you have the quickest reflexes on the planet, putting food in your mouth that has spent a little time on the floor is already contaminated.
This does not mean, however, that anything that has dropped on the floor should end up in the trash rather than in your tummy. According to scientists, there are a bunch of other factors to consider aside from the amount of time food has spent on the floor. They include the amount of moisture present on the surface of the food, the type of surface the food has fallen onto, the kind of bacteria present on the floor, and the level of contamination.
Certainly, a slice of banana will pick up more microbes than, say, a slice of bread whose surface has less moisture content. Most of the time, you can simply dust off a slice of bread and it’s good for consumption once again.
However, it’s also very important to consider where the slice of bread has fallen. If it’s on your kitchen floor that you disinfect on an everyday basis because you are a clean freak, then it is very much less likely for that slice of bread to end up contaminated with health-wrecking bacteria after it has touched your floor for a few seconds.
On the other hand, it is an entirely different picture if that slice of bread fell elsewhere, such as on the hospital floor or restaurant floor that gets heavy traffic. Needless to say, there are more bacteria present on those than on your well-disinfected kitchen floor, and many of them can definitely put your health in some form of danger.
Then you also have to consider the type of surface on which food accidentally falls — non-porous surfaces such as metal and tiles tend to harbor lots of bacteria, while porous ones like wood and carpet tend to have fewer.
Such is what some scientists found out when they applied bacterial solutions onto various surfaces while conducting experiments. They discovered that porous surfaces such as carpeted ones absorb much of the microbes in the solutions they used, thus pieces of food they dropped on various surfaces tend to pick up less bacteria.
Even though there is no truth to the 5-second rule because any food that has dropped on the floor is very much likely to pick up something that the naked eye cannot see, it’s not all the time that anything you accidentally dropped should be thrown away. But when in doubt, just throw it away — it’s not worth risking your health.