Who hasn’t tried to salvage a mouthwatering morsel tragically lost to a germ-covered floor by blurting “FIVE-SECOND RULE!” before diving to the rescue? Even the most intelligent among us might be apt to cite the tenet with the fervor of an emergency responder. But let’s face it: the chances that some magical cut-off of five seconds will spare food from irreparable defiling was always far-fetched. Still, if you need hard-hitting evidence, researchers have now provided a comprehensive study that proves the rule is down for the count.

After analyzing several floor materials, food types, contamination methods, and resting times, researchers at Rutgers show conclusively that food can easily become contaminated in less than five seconds. In fact, contamination may take less than one second in some scenarios. In a small consolation, the researchers note that the general theory behind the debunked rule—that longer resting time on a contaminated surface will increase contamination—stands.

“Our data clearly showed that contact time does influence bacterial transfer, with more bacteria transferred at longer times,” food scientists Robyn Miranda and Donald Schaffner report in the journal Applied and Environmental Microbiology. However, they conclude “that other factors including the nature of the food and the surface are of equal or greater importance.” And in the end “some transfer takes place ‘instantaneously’ at times <1 s, disproving the ‘five second rule.’”

The study isn’t the first to quash the popular rule. A few other small studies and experiments—one published, one not, and one on the TV show Mythbusters—have proven that certain foods dropped on particular surfaces can become contaminated in fewer than five seconds. But the authors of the current study wanted to crush the rule “in an extensive and comprehensive manner” and completely tease out the factors of cross-contamination.

So the researchers dropped chunks of watermelon, bread, buttered bread, and gummy candy from 12.5 cm onto contaminated surfaces made of either stainless steel, wood, ceramic tiling, or carpet. Each faux floor was coated in one of two dried culture buffers containing Enterobacter aerogenes B199A bacteria. Even though it’s harmless, Enterobacter aerogenes mimics the attachment skills of Salmonella, a common food pathogen. And food was left for either less than one second, five seconds, 30, or 300. Each condition was repeated 20 times, resulting in a total of 2,560 data points.

Each variable altered the transfer rate of bacteria to the plopped food. Generally, tile and stainless steel had the highest transfer rates. Wood’s transfer rate varied with foods, while carpet was the least likely to give up bacteria to any food that landed.

Watermelon chunks, a moist food with smooth surfaces, was the best at soaking up contamination from the floor. It became contaminated instantly in all but one condition—on carpet contaminated with bacteria in a peptone buffer. Gummy candy was the best at resisting contamination. But, the authors note, that may change if the candy is dropped from greater heights, thereby increasing the pressure and splat-factor.

Overall, there were a few instances when foods didn’t become contaminated within five seconds—notably the gummy bears on carpet. However, the authors conclude this exception isn't enough to prove the rule. They write:

The risk of illness resulting from deciding to consume food that has fallen on the floor will depend on factors including prevalence, concentration and type of organism, the nature of the food (especially moisture), the nature of the surface topology as well as the length of time the food is in contact with the surface... The 5-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food.

Applied and Environmental Microbiology, 2016. DOI: 10.1128/AEM.01838-16 (About DOIs)