Is the 5-Second Rule Valid?

I’ve heard of the 5-second, 10-second and even 30-second rule. You drop food on the floor and if you pick it up in time, then it’s okay to eat. Is this a safe rule to live by?
One of the most disgusting cases I’ve seen is a pacifier dropped on the New York subway floor. The mom picked it up, stuck it in her own mouth to clean and then right in the baby’s mouth. The pacifier was on the floor for about 5 seconds, but that’s enough time for bacteria to cling to food (or in this case a pacifier).
Bacteria love protein and carb-based foods that are moist and not too acidic. This includes foods like meat, chicken, eggs, dairy, cooked vegetables and cooked pasta. Once bacteria is on a food they love, they can double their number every 20 minutes—this means, one bacterium can become over 1 billion in about 10 hours, which is more than enough to get someone sick.
If you think acidic foods like lemons and tomatoes are safer foods, think again. In 2002, an outbreak of salmonella was reported from participants in the U.S. Transplant Games held at Disney's Wide World of Sports Complex in Orlando, Florida. The culprit was thought to be Roma tomatoes.
To most people, the textbook definition of clean means that something is free of visible dirt. But although your floor may appear to be clean, it can still have plenty of invisible microorganisms dancing around. You use chemicals to sanitize your floor to remove most of the harmful germs. But certain bacteria and viruses (like the infamous cruise-ship Norovirus) can still survive on surfaces for months. If you’re thinking you can “cook it out”—it’s important to know that some pathogens can survive in very cold and very hot temperatures.
Although you may not get sick each time you eat off the floor, the very young and very old have a weaker immune system and are more susceptible to illness. This is also one habit you don’t want to teach your kids. Imagine dining out with friends and having your child dive on the floor every time food is dropped—pretty embarrassing, to say the very least.
You may have eaten food off the floor in the past and gotten lucky. Or maybe you’ve had a little diarrhea and just didn’t put two and two together. If you want to be safe, then live by these words: when in doubt, toss it out.
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Toby Amidor, MS, RD, CDN, is a registered dietitian and consultant who specializes in food safety and culinary nutrition. See Toby's full bio »