We’re sure you’ve heard of the five-second rule, in which you have five seconds to pick up food that’s fallen off a plate and still have it be okay to eat. Well, Dr. Jorge Parada, medical director of the infection prevention and control program at the Loyola University Health System and a proessor at Loyola’s Stritch School of Medicine says otherwise, reports Newswise.com.

“A dropped item is immediately contaminated and can’t really be sanitized,” Dr. Parada is quoted as saying. “When it comes to folklore, the ‘five-second rule’ should be replaced with ‘when in doubt, throw it out.’”

This is because coming into contact with any surface exposes an item to bacteria. It’s just that the amount and kinds of bacteria it’s exposed to depends on the kind of surface it’s dropped on and the object that is dropped.

But Dr. Parada does admit to occasionally having used the five-second rule. “If you rinse off a dropped hot dog you will probably greatly reduce the amount of contamination, but there will still be some amount of unwanted and potentially nonbeneficial bacteria on that hot dog. Maybe the dropped item only picks up 1,000 bacteria, but typically the innoculum, or amount of bacteria that is needed for most people to actually get infected, is 10,000 bacteria – well, then the odds are that no harm will occur. But what if you have a more sensitive system, or you pick up a bacteria with a lower infectious dose? Then, you are rolling the dice with your health or that of your loved one.”

Exposure, Dr. Parada explains, can be compared to being burned, where temperature is like the type of bacteria on a surface, while time is like the amount. "The hotter the surface the easier and worse you will be burned—like the more virulent, or harmful, the bacteria the easier and sicker you may get. One only has to touch a white hot surface momentarily to get burned and sometimes it doesn’t take a lot of bad bugs for you to get sick. On the other hand, if hold your hand to a less hot surface, but do so for a longer period, the more you will be injured, too."

Dr. Parada explains that contamination risk also depends on the type of surface the food lands on and the type of food that falls. For example, if food fell off a plate and on to a table, the risk of contamination would be less than if it had fallen on the floor. Also, he says, "In the same time period, a rock candy is less likely to pick up contamination than a slice of cheese. As an extreme example, whether it’s a rock candy or a slice of cheese, I dion’t think anyone would invoke the five-second rule if it fell in the toilet."

(Photo by Jeroen Wiersma via sxc.hu)