Food on the Floor? Why the Five-Second Rule is Actually True

Remember your days in the school cafeteria when you or someone else would drop that beloved Oreo on the ground? At first it was thought to be lost forever until everyone yelled "Five-second rule!" and someone scooped it off the floor.

Researchers at Aston University in Birmingham, England have found evidence to support the five-second rule, even after previous studies have refuted it. Past research is correct in their assertion that bacteria on the floor will immediately transfer onto the food when dropped on the ground. But different bacteria and different surfaces are important factors when the food is dropped.

The Aston University researchers tested four different surfaces, including tile, laminate, wood, and carpet. They also tested various foods with different textures and degrees of moisture, including toast, pasta, biscuits, gam, fruits, and sticky desserts. The lengths of time the foods were left on each surface varied from three seconds to thirty seconds.

The study found that the tile, wood, and laminate surfaces transfer bacteria much quicker than carpet surface and that moist foods were more likely to pick up bacteria than dry foods. Additionally, the bacteria didn't immediately transfer to the food when it hits the ground. All of these findings were parallel with previous studies' findings.

However, the research differs in terms of the degree of food contamination. Professor Anthony Hilton, the leader of the Aston University study, found new evidence in terms of bacteria infestation of the food.

"The initial transfer [of bacteria to food] is insufficient [to contaminate the food]," he said in this National Geographic article. In our study only one millionth of the bacterial population present on the floor was transferred to the dry food, and approximately 20 times more to the moist. For moist foods, on these flooring types, there is underpinning evidence that fewer bacteria will be transferred to food picked up quickly."

But do people actually eat food that they've dropped on the ground? The study revealed a resounding "yes", with 87% of people surveyed responding affirmatively. However, we should all be careful, because if a piece of food is left on the ground for minutes the contamination will be stronger and you'll be more likely to get sick or spread to other foods nearby.

To read more about the Aston University study, visit this National Geographic article as well as this New York Daily News article.