Wednesday, 1 March 2017

The 5-second rule: When Is It Really Safe To Pick up and Eat Foods That Fall On The Floor?

The 5-second rule
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Is It really safe to pick up and eat Foods that fall on the floor before 5 Seconds? Very interesting question if you ask me. I know you probably must have heard of the five-second rule somewhere, somehow, and you have absolutely no clue how valid this well-adopted rule is. However, if you're coming across this for the first time, the 5-second rule is a 'so-called' food hygiene practice stating that food (or sometimes cutlery) dropped on the ground will not be significantly contaminated with bacteria if it is picked up within five seconds of being dropped. As funny as it may sound, many of us actually believed and applied this rule while growing up; and it gained so much popularity in households, restaurant kitchens, schools and almost anywhere people prepare or consume food. 

Read More: Patient Zero: First Recorded Cases of 8 Common Deadly Disease Outbreaks In History.

Well, we at ScienceHealth24 got a little curious and did some digging. It turns out that the 5-second rule, where food is apparently 'safe' to eat if dropped on the floor and picked up within 5 seconds isn't actually true and there are facts to prove it. Some may truly believe this assertion, whereas most people employ the rule as an amusing social fiction that allows them to eat a dropped piece of food, despite the potential reservations of their peers. Researchers, by testing various foods on different surfaces to see how fast bacteria transfers to it, found that bacteria can jump on our dropped snacks in under 1 second, which of course is very bad news for big eaters everywhere, including myself.
According to Donald Schaffner, a member of the research team from Rutgers University, 

"The popular notion of the '5-second rule' is that food dropped on the floor, but picked up quickly, is safe to eat, because bacteria need time to transfer,"

"We decided to look into this because the practice is so widespread. The topic might appear 'light', but we wanted our results backed by solid science."
The team performed an experiment using four different types of surfaces - stainless steel, ceramic tile, wood, and carpet - and selected a number of different foods to drop on them, including watermelon, dry bread, buttered bread, and gummy candies. They grew Enterobacter aerogenes - a safe, non-pathogenic relative of Salmonella - in the lab, and covered their test surfaces in it.

Each piece of food was then dropped on each bacteria-covered surface, and left there for various amounts of time: 1 second, 5 seconds, 30 seconds, and 300 seconds. A total of 128 different scenarios trials were completed and replicated 20 times, adding up to 2,560 individual measurements that were used to analyse the amount of contamination on each food item.
The team discovered that the biggest factor when it came to bacteria transfer was the amount of moisture present in the food, followed by the type of surface it's being dropped onto. And while bacteria didn't hesitate to transfer over, the longer food was left on the surface, the more bacteria jumped on the food.
Schaffner said, "Transfer of bacteria from surfaces to food appears to be affected most by moisture. Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer. Also, longer food contact times usually result in the transfer of more bacteria from each surface to food."

The team says that even though they found that longer contact times did lead to higher levels of contamination, picking up food in less than 5 seconds is still enough time for bacteria to transfer - especially if the food is wet or sticky like watermelon or candy, which had the highest levels of contamination across the tests.

"The 5-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food," Schaffner says. "Bacteria can contaminate instantaneously."
There were some surprising finds, too. You would think that surfaces covered with Carpet, with its tendency to catch crumbs and get dirty rather quickly, would be bad; but the researchers found that it's actually the best surface because its structure minimises the amount of contact it has with the food.

The Rutgers team isn’t the first to debunk the 5-second rule. There have been other studies about it and TV shows have tackled it, too. But they hope that their concrete analysis of different types of foods and surfaces will help people to understand how the popular piece of advice is not something you want to base your hygiene practices around.
The team’s work was published in Applied and Environmental Microbiology. You can read more on another Independently conducted experiment to test the 5-second rule by a high school senior Jillian Clarke, during a six-week internship in the food science and nutrition department at the University of Illinois at Urbana-Champaign. Well, that's all I have to say. Thanks for reading. There are so many new ways to share this article with your friends on social media and it would only take less than a second. Also, subscribe to our newsletter to get more amazing updates to your mail. Don't be shy, share your opinions in the comments below.


  1. It was informative but I think I won't be stopping with 5-second rule anytime soon because I just love food that much and can't waste it.

    1. Hahaha... You're funny. Thanks for reading this.