You are just about to eat the last chocolate that you have been saving all day, but as it reaches your mouth, you drop it on the floor. Do you throw it away? Or do you pick it up, give it a quick wipe and eat it? Many of us would refer to the "5-second rule" to justify eating it. Now, new research suggests this urban myth may actually hold scientific fact.
The 5-second rule is the theory that if food is retrieved within 5 seconds of being dropped on the floor, it is safe to eat because there has not been enough time for bacteria to contaminate it.
To see whether this theory holds some truth, the research team, led by Prof. Anthony Hilton of Aston University in the UK, assessed the transfer of common bacteria - Escherichia coli and Staphylococcus aureus - between various floor types and foods.
The floor types assessed were carpet, laminated and tiled surfaces, while the foods monitored included toast, pasta, a biscuit and a sticky candy.
The researchers analyzed the level of bacterial transfer when foods were in contact with floor surfaces for between 3 and 30 seconds.
5-second rule 'much more than an old wives' tail'
Results of the analysis revealed that time is a significant factor in how much bacteria is transferred - the longer food is left on the floor, the more bacteria it picks up.
Furthermore, the type of floor surface food is dropped onto has a bearing on the amount of bacteria transferred.
The research team found that bacteria is least likely to transfer from carpeted surfaces and most likely to transfer from laminate or tiled surfaces to moist foods that make contact for more than 5 seconds.
As part of the study, the investigators also conducted a survey that asked participants whether they use the 5-second rule.
Results revealed that 87% of partipants had already eaten food dropped on the floor, or would do so. Of these, 55% were women. Of the women who said they would eat food dropped on the floor, 81% said they would adopt the 5-second rule.
Given the large amount of people who eat food that has been on the floor, Prof. Hilton says the team's findings should put people's minds at ease:
"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 5-second rule for years, despite a general consensus that it is purely a myth."
Overall, Prof. Hilton says their findings show that the 5-second rule is "much more than an old wives' tale."
By contrast, in a 2012 report from Medical News Today, Dr. Jorge Parada, of Loyola University in Chicago, suggests that the 5-second rule is incorrect, and that food dropped on the floor is immediately contaminated and cannot be sanitized.
He says when it comes to folklore, the 5-second rule should be replaced with: "when in doubt, throw it out."