The Five-Second Rule: Scientific Fact or Psychological Reflex? Here’s What Science Says!

Written by Henrik Rothen

May.20 - 2024 2:04 PM CET

Is the five-second rule a microbiological truth or just a psychological habit? Science has weighed in on this longstanding debate with intriguing insights.

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We've all heard it before: if you drop food on the floor, you have five seconds to pick it up and eat it without risking any contamination.

This so-called five-second rule has been a common belief since childhood, often more of a playful habit than a true conviction. But does it really hold any scientific merit?

Immediate Bacteria Transfer

The crux of the five-second rule lies in how quickly bacteria can contaminate food.

In 2007, food scientist Paul Dawson from Clemson University conducted one of the few scientifically rigorous studies on this topic.

His research concluded that food picks up bacteria as soon as it touches the floor.

There’s no grace period where your food remains germ-free.

Factors Affecting Bacteria Transfer

The story doesn’t end there.

Donald Schaffner, a food scientist at Rutgers University, along with his student Robyn Miranda, expanded on Dawson’s work in 2016.

Their experiments considered various foods and surfaces, revealing that while bacteria transfer is immediate, the amount of bacteria depends on several factors:

  • Type of Food: Moist foods like watermelon, apple slices, and tomatoes pick up more bacteria than drier foods such as biscuits or bread.

  • Type of Surface: Carpeted floors transfer fewer bacteria compared to tile or stainless steel. Additionally, other surfaces like unwashed hands, utensils, and cutting boards can also introduce bacteria.

A Psychological Comfort Rather Than a Scientific Truth

So, is it dangerous to eat food that’s been on the floor?

Generally, no. Schaffner's findings indicate that "ninety-nine percent of the time, it's probably safe."

The National Geographic article that covered these findings sums it up well: the five-second rule is more about psychological comfort than scientific fact.

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