Is there any truth to the '5-second rule'?

Uh oh. You just dropped your toast on the floor. It was the last piece, too. And you were enjoying it so, so much.

You know where this is going.

Since childhood, most of us have been aware of — and perhaps practiced — the five-second rule, which purports that any food item that’s accidentally dropped on the floor will not be significantly contaminated with bacteria if it’s picked up within five seconds. It’s a notion so engrained in our consciousnesses that it’s even got its own Wikipedia page.

But can the “five-second rule” be trusted?

What do the studies say?

Not surprisingly, the so-called “rule” has been put to the test numerous times, often with the same conclusion: Food that touches the floor can be contaminated with bacteria almost immediately, but the level of bacterial still depends on where the incident happens, what type of food it is, and how long it sits there.

In one study from 2016, professors at Rutgers University determined that bacteria transfer could take place within a second, which is far too quick for most people to retrieve any dropped foods. But after evaluating different types of foods (wet foods, dry foods, sticky foods, etc.) and different types of flooring (wood, tile, carpet, stainless steel), they concluded that foods gather more bacteria the longer they remain on the ground.

They also found that wet foods picked up the most bacteria, and that carpeting had the lowest “transfer rates” — echoing two discoveries that researchers with Aston University in the U.K. made in a similar 2014 study, per Scientific American.

Going viral

In recent weeks, however, the reliability of the “five-second rule” again made headlines after TikTok creator identified as Nick Aicher, also a quality control analyst at a bioengineering firm, tested the theory in a viral video. He ultimately determined that, yes, your dropped food is somewhat more gross no matter how quickly it’s retrieved from the floor.

In the video, Aicher studied petri dishes with films that had been exposed to a surface for zero seconds, five seconds, 10 seconds, 20 seconds and 30 seconds, and then allowed those samples to incubate. He found that bacteria had transferred to all of his samples, and declared in an on-screen message that “even 0 seconds is too long” to leave food on the ground.

Aicher also claimed the 10-second and 20-second samples showed more bacteria, while the 30-second sample had a “big boy” — i.e., a large bacterial growth — growing in it.

Aicher was not immediately available to discuss his findings with SavorNation.

It’s ‘a gamble’

Nicole Nomides, an infection prevention specialist who formerly worked with the University of Michigan Health System, also once agreed that five seconds is more than long enough for bacteria to transfer from the floor to your food. And even though she claimed you likely won’t get sick from eating it anyway, she said it’s still “a gamble.”

“As far as I’m concerned, the world is one big petri dish,” Nomides said.