Why Do We Keep Following This Childhood Food "Rule"?

If you’ve ever dropped food on the floor and quickly picked it up to eat it, you’re probably familiar with the "Five-Second Rule." For those who aren’t, it’s an old saying that claims food remains safe to eat if you grab it within five seconds of hitting the ground. But does this rule hold any truth, or is it just a persistent myth? And why has it become such a common habit? We spoke with food safety experts to get their thoughts on the matter.

Where Did the Five-Second Rule Originate?

The Five-Second Rule refers to the practice of eating food after dropping it on the floor, as long as it's picked up quickly. However, Kristen Nauss, MS, MBA, RD, SNS, a registered dietitian and founder of Buying School Food, argues that this "rule" is nothing more than an outdated myth.

Nauss traces the origin of the Five-Second Rule back to the 13th century, attributing it to Genghis Khan, the Mongol emperor. Legend has it that if food fell on the floor during one of his banquets, he would determine whether it was still acceptable to eat.

Over time, Khan's practice evolved into a common household tradition. The belief is that if food falls onto the floor for five seconds or less, it's still safe to eat because there's not enough time for harmful germs to contaminate it.

The Science Behind the Five-Second Rule

However, research shows it can take less than five seconds for food to pick up harmful bacteria, such as Salmonella or E. coli, says Lisa Yakas, Senior Account Manager at NSF’s Global Food Division.

Multiple studies, including a 2021 research from the Journal of Food Protection, have debunked the five-second rule. The study revealed that bacteria from grocery store floors were immediately transferred to produce the moment it touched the ground. Yes, immediately.

While public spaces are definitely riskier, your home floors aren't completely free from germs either. Even if your kitchen floor looks pristine, invisible bacteria and pathogens could still be lurking there.

Yakas points out, "Wherever you are, floors can harbor bacteria that can transfer to your food and potentially make you ill."

The longer food remains on the floor, the more bacteria it picks up. A 2016 study also found that foods high in moisture, like watermelon or cucumber, attract even more germs when dropped on the floor.

However, the likelihood of getting sick from eating food that has touched the floor, no matter how long it’s been there, is generally the same. This risk is heightened for children, older adults, and individuals with compromised immune systems or underlying health conditions.

What to Do With Dropped Food

Trust your instincts! If the food has a peel or skin you can remove or wash off, it might still be safe. Otherwise, unless you plan to cook the food (since heat can kill bacteria), it’s probably best to discard it. Yakas advises, "It’s better to throw it away." Unfortunately, this childhood myth holds about as much truth as believing in the tooth fairy.