The five-second-rule myth is a myth

By Toby Manhire In Science, The Internaut

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20th March, 2014 Leave a Comment

A significant update. Just less than a year ago, we conveyed the news that a real-life scientist at the University of London had scotched the five-second rule.

Experiments for the BBC News Magazine showed that bacteria stuck just as much to dropped food “whether it’s one second or 10”.

This came as quite a jolt to those of us who have over the years developed a special skill for scooping toast, biscuits, and other similar items from the floor with alacrity.

But now – brace yourself – a research project led by Anthony Hilton, professor of microbiology, at Britain’s Aston University, has found evidence to the contrary.

This from Science Daily:

The study, undertaken by final year Biology students and led by Anthony Hilton, Professor of Microbiology at Aston University, monitored the transfer of the common bacteria Escherichia coli (E. coli) and Staphylococcus aureus from a variety of indoor floor types (carpet, laminate and tiled surfaces) to toast, pasta, biscuit and a sticky sweet when contact was made from 3 to 30 seconds.

The results showed that:

– Time is a significant factor in the transfer of bacteria from a floor surface to a piece of food; and

– The type of flooring the food has been dropped on has an effect, with bacteria 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.

Professor 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; however the findings of this study will bring some light relief to those who have been employing the five-second rule for years, despite a general consensus that it is purely a myth. 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.”

The evidence, Hilton says, tells him that the five-second rule is “much more than an old wive’s tale”. (Actually, it says, “old wives’ tail” but let’s not read anything into that.)

We promise to keep you up to speed with all five-second-rule science developments.

Update: Nine to Noon has tackled this revelation, raising a suspicious eyebrow at the reliability of the non-peer-reviewed study.


See also: The five-second rule – true or false

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