The five-second rule
John L. Po, MD, is an infectious disease specialist at Banner Estrella Medical Center. His office can be reached at 623-327-4144.
Question: People often joke about the five-second rule when dropping food on the ground. Is it really safe to eat food once it has touched the ground?
Answer: It's probably safe to say that we have all, whether we will admit it or not, eaten food that has been dropped on the ground. After all, the "five-second rule" tells us that it's safe to eat food that has touched the floor as long as you pick it up in five seconds or less, right?
Are you willing to bet your life on it?
Regardless of how fast you pick food off the floor, you're taking a risk. Bacteria, fungi and viruses can be present on any surface. Though factors such as the type of flooring, the amount of moisture in the food dropped and room temperature can influence how quickly and how much germs will contaminate the food, it occurs well within five seconds. A study by Clemson University in 2007 found that when a piece of bologna was dropped on wood, tile and carpet flooring, bacteria were transferred to the piece of meat instantaneously.
Eating food that has been dropped briefly on the floor doesn't guarantee that you will get sick; however, you are taking a risk. Ingesting potentially harmful bacteria (such as salmonella) that just piggy-backed on your buttered toast increases your risk, with as few as one to 10 bacteria, causing diarrhea, vomiting, and other gastrointestinal problems.
Therefore, as tempting as may seem to dismiss the risk of infection after dropping food onto even the shiniest floor, here's some food for thought:
- You really don't know what's been left on that very spot where someone might have walked over with their boots.
- Even if you do pick your food up within five seconds, you will always have some germs clinging on to it.
- It doesn't take much of these germs to cause infection.
- When in doubt, throw it out.
Finally, don't forget to wash your hands after tossing that dropped piece of food.
Reviewed March 2011