Curiosities: Is there any validity to the so-called 5-second rule?

If a piece of toast fell on the floor, would you pick it up and eat it? You probably would if you believe in the 5-second rule, which suggests that your spilled breakfast stays germ-free as long as you snatch it up in five seconds.

But while the 5-second rule remains a popular rule of thumb, there is no hard science to support it, says Glenn Chambliss, a bacteriologist at UW–Madison. In fact, if you dropped food in places harboring nasties like E. Coli bacteria, any contamination would happen instantaneously, the scientist says.

In today’s sanitized environments, however, chances of dropped foods landing in germ-infested areas are very small. And even when a few stray germs do latch onto food particles, the human body’s defense system can easily fight them off, Chambliss says.

Obviously, eating food off the floor gets riskier the longer it has been lying there. Moist or damp foods are also more prone to contamination because they make more contact with the ground. Retrieving food outdoors is also generally safe, says Chambliss, as long as it doesn’t fall on potential reservoirs of infection such as piles of animal poop.