Anthony Hilton, a professor of microbiology at Aston University in England, monitored the transfer of the common bacteria E. coli and Staphylococcus aureus from a variety of indoor floors, including carpet, laminate and tiled surfaces, to toast, pasta, biscuit and a sticky sweet when contact was made from 3 to 30 seconds.
The researchers found time was a significant factor in the transfer of bacteria from a floor surface to a piece of food and the type of flooring also had an effect.
Bacteria were least likely to transfer from carpeted surfaces and most likely to transfer from laminate or tiled surfaces to moist foods making contact for more than 5 seconds, Hilton said.
"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 but 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," Hilton said in a statement.
"We have found evidence that transfer from indoor flooring surfaces is incredibly poor with carpet actually posing the lowest risk of bacterial transfer onto dropped food."