Should you eat food that fell on ground if it was picked back up very quickly?

There is an opinion that it is still safe if you pick up within 5 seconds the food that has fallen on the ground. And researchers have solved this problem, reports Popular Science.

In 2003, Jillian Clarke, a senior at the Chicago High School for Agricultural Sciences in Illinois, put the five-second rule to the test. She inoculated two types of tiles—smooth and rough—with Escherichia coli and dropped gummy bears and cookies on the tiles for five seconds. Clarke and her coworkers saw that bacteria transferred to food very quickly, even in just five seconds, thus challenging the popular belief.

A few years later, food scientist Paul Dawson and his students at Clemson University in South Carolina also tested the five-second rule and published their results in the Journal of Applied Microbiology. When they dropped bologna sausage onto a piece of tile contaminated with Salmonella typhimurium, over 99% of the bacteria transferred from the tile to the bologna after just five seconds. The five-second rule was just baloney, Dawson concluded.

But in 2014, microbiology professor Anthony Hilton and his students at Aston University in the United Kingdom reignited the debate. They studied the transfer of E. coli and Staphylococcus aureus from a variety of indoor floor types (carpet, laminate, and tile) to toast, pasta, biscuit, and a sticky sweet, with contact times ranging between three to 30 seconds. According to their results, the longer a piece of food was in contact with the floor, the more likely it was to contain bacteria. This could be interpreted as evidence in favor of the five-second rule, Hilton noted, but was not conclusive.

This prompted food science professor Donald Schaffner and his master’s thesis student, Robyn C. Miranda, at Rutgers University in New Jersey to conduct a rigorous study on the validity of the five-second rule, which they published in the journal Applied and Environmental Microbiology. They looked at bacterial transfer to four different foods (watermelon, bread, bread with butter, and gummies) when dropped on four different surfaces (stainless steel, ceramic tile, wood, and carpet) contaminated with Enterobacter aerogenes. They found that longer contact times resulted in more transfer, but some transfer took place “instantaneously,” after less than 1 second, thus debunking the five-second rule once and for all.

Your chance of falling ill after eating food that has touched the floor depends on factors like how contaminated the floor is and the type of bacteria present, said Charles P. Gerba, a microbiologist and professor of virology at the University of Arizona.