It’s a rule many adhere to but few will actually own up to following: If your food falls on the ground, you’ve got a few seconds—let’s say... five?—to pick it up and eat it.
Up to this point, it’s been little more than a handy way of getting around the social norm that eating food off the floor is, well... gross. But a new study from Aston University in Birmingham, England, suggests that the five-second rule may actually have a scientific basis. And the details are fascinating.
Researchers at the university tested the hypothesis that food might need to spend a certain amount of time in contact with a given surface to pick up bacteria. To do so, they dropped a variety of foods on a variety of indoor flooring types treated with E. coli and Staphylococcus aureus bacteria. They let each piece of food sit on the surface for between 3 and 30 seconds, then checked the food to see if bacteria had been transferred.
Results revealed that food dropped on smooth surfaces like tile or laminate is far more likely to pick up bacteria than similar food dropped on carpet. And, as logic would suggest, moist foods are almost certain to grab anything they come in contact with.
The study was led by Anthony Hilton, Professor of Microbiology at Aston. He cautions that while the results point to a correlation between contact time and infection risk, that doesn’t mean the five-second rule can be taken as a guarantee of safety:
“Consuming food dropped on the floor still carries an infection risk as it very much depends on which bacteria are present on the floor at the time; however the findings of this study will bring some light relief to those who have been employing the five-second rule for years, despite a general consensus that it is purely a myth.”
Of course, the study was undertaken in lab conditions, where every tested surface was coated with dangerous bacteria. In the real world, where the five-second rule is actually employed, your circumstances will be far more varied.
In tandem with the lab study, Hilton’s students conducted a survey to determine how many people actually use the rule. The results? A whopping 87% of respondents said they would eat food dropped on the floor.