Study Backs Up Five-Second Rule

Man dropping his chips

One second you’re taking a bite of that delicious cookie, and the next thing you know, it’s on the floor. What do you do? If you’re a believer in the five-second rule – the idea that food is safe to eat until it has been on the ground longer than five seconds – you may just snap it up and keep on munching. But does science back you up?

While this question has been hotly debated and studies have yielded conflicting results, the most recent study looking into the five-second rule may be reassuring for adherents. A group of biology students at an English university measured how much E. coli and Staphylococcus aureus bacteria was transferred to a variety of foods when they were dropped. They tested toast, pasta, cookies and candy after each was dropped on carpet, tile or laminated flooring and left there for anywhere from 3 to 30 seconds.

They found that the amount of time the food spent on the floor and what type of surface it was dropped on largely determined how much bacteria adhered. Bacteria were much less likely to stick to the food if it was dropped on carpet and if it was picked up within five seconds. Sticky foods (the candy and pasta) and foods dropped on laminated or tiled flooring were more likely to accumulate bacteria.

The researchers warned, however, that eating any dropped food still carries an extra infection risk, since a certain amount of bacteria will adhere immediately. Whether or not you get sick may depend not just on how much bacteria is on the food, but also what type it is. A 2007 study, which looked at Salmonella, found that there was no safe amount of time for dropped foods.

The researchers also conducted a survey that showed that 87% of people said they either had or would eat food that had been dropped on the floor, and that women were slightly more likely to eat dropped food than men.

The study has not yet been published in a peer-reviewed journal.