I have been a firm believer in the five-second rule for as long as I can remember. Honestly, I have no idea if my parents taught me this or if it's something I learned in school, but you'd better believe if some food drops on the floor I will eat it within five seconds.
Lucky for me, scientists decided to test this rule once and for all and published the study in the journal "Applied and Environmental Microbiology." The result? No, it doesn't take five seconds for bacteria to transfer to your food.
Scientists left watermelon, bread, bread with butter and gummy candy on multiple different surfaces that were all contaminated with different bacteria. The food was all left for periods of one, five, 10 or 300 seconds. For some of the bacteria, it took less than one second for it to transfer to the food. The good news is, though, that the longer the food was in contact with the surface, more bacteria transfer occurred. Meaning if you pick up your food within five seconds it actually does prevent more bacteria from transferring.
According to the study, “other factors including the nature of the food and the surface area are of equal or greater importance” -- specifically, “Carpet has very low transfer rates, compared with tile and stainless steel, whereas transfer from wood was more variable.”
Following the study, physician Aaron E. Carroll posted a column in the New York Times about this so-called "five-second rule." According to him, the time your food spends on the floor should be the least of your worries.
“Our metric shouldn’t be whether there are more than zero bacteria on the floor,” Carroll wrote. “It should be how many bacteria are on the floor compared with other household surfaces. And in that respect, there are so many places in your house that pose more of a concern than the floor.”
He makes a good point, considering previous studies have found that your refrigerator handle and kitchen counter harbor more bacteria, on average, than the kitchen floor.
The moral of the story? Wash your hands, wipe down your counters and if a piece of toast falls on the floor, go ahead and eat it.