Graduate Students Test 5-second Rule

Graduate students at Aston University studied the transfer of common bacteria Escherichia coli (E. coli) and Staphylococcus aureus from flooring surfaces to various types of food items.

This is a research study which actually sets out to analyze the truth of the “5-second rule” – when you supposedly are safe to eat something that has only been on the floor for less than 5 seconds after being dropped. Surprisingly, the study shows that indeed, the “5-second rule” holds muster.

The Study Studied Multiple Floor Surfaces

The study looked at a variety of floor surfaces (carpet, laminate, and tile), as well as toast, pasta, biscuits and a sticky candy making contact for between 3 to 30 seconds. They were looking specifically at the degree to which bacteria transferred to the dropped food item over a given period of time. The results may not be what you think. Time is obviously a significant factor, with 5 seconds is within a window where not much bacteria is transferred. Floor type is also a factor, with carpet having the least amount of bacteria transfer. The lead author was adamant in stating that: “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.” She also vindicates the “5-second rule,” and states that the “evidence that transfer from indoor flooring surfaces is incredibly poor.”

Everyone Does It

And it does appear that most people do eat off the floor, so if you’ve been self-conscious about eating that carrot stick that just dropped off the cutting board, you can stop worrying about it; you’re in good company. The Aston team surveyed a number of people and found that 87% of people surveyed said they would eat food dropped on the floor (or already do). And most of them are firm advocates of the “5-second rule.”

Eat Up That Floored Chip, Burrito, Ice Cream Cone

In all seriousness, this is great support for not worrying about most of the bacteria that is living and growing around us all the time. It further supports the notion to trust our immune system and allow it to do the work it is there to do. Additionally, it spurs the question of whether it is “safer” to sanitize EVERYTHING and encase everything in supposedly sterile plastic. Maybe there’s not a lot of bacterial transfer in 5 seconds, but perhaps it also doesn’t matter.


Node Smith, associate editor for NDNR, is a fifth year naturopathic medical student at NUNM, where he has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine amongst the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend campout where naturopathic medicine and medical philosophy are experienced in nature. Three years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision. 

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