Debunking the 5 Second Rule

Picture this: it’s lunchtime, and you just whipped up grilled cheeses, pretzels and ants on a log for your hungry kids. Your 4-year old grabs his plate a little too eagerly… and the food falls everywhere.

You:

  • A. Rapidly place the sandwich, logs and pretzels back on the plate for your kiddo — five second rule!
  • B. Place the pretzels and sandwich back on the plate after dusting them off. The logs, meanwhile, have little fuzzes and specks of dirt on them, so you toss ’em.
  • C. Throw everything away, and remake the entire lunch.
  • D. Remake lunch — as you scarf down the from-the-floor lunch — five, er, fifteen second rule!

You’ve probably heard of the old “five second rule,” and wondered, “Is it valid?” “Is it safe to eat food that’s been on the floor?” Does where the food fall matter? Is food that falls outside safer than food that falls inside? What are the exceptions?

Well, today we’re answering these questions — and more!

The Five Second Rule
Noun. This rule states that any food that falls on any surface is safe for consumption so long as it’s retrieved within five seconds of its landing.

The common understanding of the five second rule is that food that’s only been on the ground a few seconds surely hasn’t picked up enough germs to make you sick. Right?


The Science Behind the Five Second Rule

Here’s the short answer: food retrieved within a few seconds after being dropped is less likely to contain bacteria than if its been left for longer periods of time, according to a study conducted at Aston University’s School of Life and Health Sciences in England.

This study also confirmed that the type of surface on which the food has been dropped has an effect, with bacteria least likely to transfer from carpeted surfaces.

It seems counter-intuitive that carpet is cleaner than wood, at least in terms of the five second rule. Doesn’t carpet trap dirt? Well it’s actually carpet’s dirt-catching properties that make it better for dropped food, because the carpet fibers “hold” the dirt and make it less transferable. Meanwhile, smooth surfaces like tile or laminate transfer dirt upon contact because there’s no buffer.

Moreover, the type of food matters: germs transfer more easily to moisture-rich foods like meats, fruits and veggies than to dryer foods like breads and crackers.


Seconds, Minutes, Hours

Some people abide by the “five second rule,” others cite a “10 second rule” — does it matter?

Research has found that, when food falls, there is an initial transference of germs, no matter the type of food or surface. But, we all know that some germs are ok — kids need a little dirt to build up their immune systems!

Have you heard of the “hygiene hypothesis?” Basically, research has shown that kids need a little dirt: the problem with extremely clean/sterile environments is that they fail to provide the necessary germ exposure required to ‘educate’ kids’ immune systems. In other words, kids need to be exposed to germs in order to build up their immunity.

However, foods left longer than 30 seconds (especially moisture-rich foods), contained up to 10 times more bacteria than food picked up after three seconds.

In other words, you should aim to pick up the fallen food as quickly as possible. And, those cheerios you found in your child’s car seat from… um… last week? Pitch them!


Implementing the Five Second Rule

  • Think about where the food fell: your kitchen floor is probably cleaner than a restaurant. And… you probably shouldn’t eat anything that fell on a bathroom floor, five seconds or not!
  • Consider how long the food was on the floor — a few seconds or a few minutes?
  • What type of food fell? Something dry, like a tortilla chip? Or a plate of carrots and hummus?

So, in conclusion — yes, there seems to be some validity to the five-second rule!

However, remember that germs transfer to food upon contact, no matter what. But, a few germs are (generally) okay, so use your judgement.

And if your fallen food doesn’t pass the five second test — well, that’s what dogs are for!

For more on the fascinating science behind germs and gross behaviors, check out: Picking Your Way to a Better Immune System, about (you guessed it): nose picking!

Photo Credits: Sarah M.
Sources: 1. Scientific American, 2. FDA.

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Sarah

Sarah is a yoga practicing, mostly vegan, coffee chugging, Jack White-loving, stay-at-home-mom to three kids 4 and under in Cincinnati, Ohio. In her free time, she does freelance work for Cincinnati Parent, Dayton Parent and Indy's Child, and blogs about her adventures with three kids in the Queen City.

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