The 5-second rule: everyone knows it, everyone has abided by its powerful law at one time or another. And while most of the time it's comedically used as an evasive veil to mask a somewhat gross action, research has shown light that there may actually be some backing.
Scientists at Aston University conducted a study thoroughly examining the infamous 5-second rule, in which they determined the time it truly takes for bacteria to transfer to food. There are 3 primary strains of infectious bacteria that potentially live on the floor, which are: E. coli, S. aureus, and salmonella. Infection from these can cause a long list of issues, from diarrhea to skin infections, to pneumonia. Ultimately, the fear of contamination is not unsubstantiated. But how likely is it for these harmful pathogens to make it onto your food?
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The research conducted confirmed that within a few moments of hitting the ground bacteria, including these three, transfers from the floor to your food. However, it takes significantly longer for a sufficient amount to transfer to actually contaminate your food enough to result in illness or adverse symptoms. Therefore, the 5-second rule is generally valid in fairly hygienic floors (this does not apply to the streets or public bathroom floors).
Interestingly enough the type of food and surface also proved to have main effects. Carpet proved to transfer less bacteria than hard-surfaces such as tile or wood. Further, moist foods were more likely to gather bacteria than dry foods.
Even more fascinating is the current theory that introduction of some of these bacteria may be beneficial for your body's immunity. The human microbiome is responsible for mediating endless bodily functions, ranging from digestion to mood. Introduction of new bacteria has been demonstrated to increase the body's ability to fight infection and illness, providing the possibility that eating off the floor, when done in the right circumstances, may be better for you than not.
While this theory currently has some supportive evidence and logic, it has been disputed and contradictory evidence also exists. So keep in mind when you're picking up the half-sandwich that slipped out of your hand, that as long as the floors are occasionally cleaned, you'll probably be alright, maybe even a little better.
