Is the “five-second rule” legitimate?

📓 The short answer

While time is a factor for how many bacteria contaminate dropped food, the five-second rule is not a legitimate food safety guideline. Bacteria transfer almost immediately on contact, and dropping food on wet or flat surfaces increases the chances of contamination.

📚 The long answer

You may have heard that if you pick up dropped food within five seconds after it hits the floor, it’s still safe to eat. But is there any truth to this rule of thumb?

When you drop food, the bacteria living on the floor will adhere to it. How many bacteria transfers depends on three factors: time spent on the floor, wetness of food, and where it landed.

Factor #1: Time spent on the floor

There is a touch of truth to the "five-second rule": Research suggests that the less time the food spends on the floor, the fewer bacteria it picks up. A 2003 study found that cookies and gummy bears retrieved in under five seconds had significantly less E. coli than those left longer.

However, fewer bacteria doesn’t mean zero bacteria. For some pathogens, like Salmonella, a little goes a long way: some studies suggest as few as 10–100 bacteria can make you sick. And a 2007 study found that Salmonella can last up to 28 days on dry surfaces and transfer to food immediately upon contact.

Factor #2: Wetness of food

For wet foods, you should really have a “zero-second rule.” Moisture helps bacteria transfer from the floor to your food. This is because moisture acts like a vehicle for bacteria. A dry surface can't transfer bacteria onto food nearly as easily as a wet one can.

That's why studies consistently find that wet hands, wet gloves, and moist surfaces transfer far more bacteria than dry ones. A dropped grape or a wet slice of deli meat picks up contamination almost instantly, while something dry, like a cracker, gives bacteria less to grab onto and less time to make the jump.

Factor #3: Where the food landed

Where you drop the food also plays into the risk of getting a food-borne illness. Places like kitchens and bathrooms tend to harbor more harmful bacteria due to food preparation, spills, and moisture.

Flat, hard surfaces like tile and wood also make it easier for germs to transfer than surfaces like carpet. Part of the reason carpet performs better in these tests comes down to its structure. Its fibers can trap bacteria or let them work down into the material, meaning fewer of them stays exposed to transfer onto food that you dropped.

Verdict: The "five-second rule" is scientifically false.

Because bacteria can transfer to food so quickly, following the "five-second rule" is definitely not a science-backed food safety guideline. But if you’re going to abide by it, at least skip eating wet food you've dropped in a kitchen, and, at the very least, wash it before taking a bite.

--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) ​ All my best, Caitlin ​Click here to read five facts about Caitlin​

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​Sources for this week's newsletter​

🌐 Wikipedia article of the week

​Great Michigan Pizza Funeral​

"The Great Michigan Pizza Funeral ... was the ceremonial disposal of 29,188 frozen cheese-and-mushroom pizzas in Ossineke, Michigan, on March 5, 1973. The manufacturer, Ilario "Mario" Fabbrini, had been ordered to recall the pizzas by the U.S. Food and Drug Administration after initial tests suggested the presence of botulism-causing bacteria in a batch of canned mushrooms.

Fabbrini decided to ceremonially dispose of the pizzas to demonstrate accountability and receive publicity. The pizzas were tipped into an 18-foot (5.5 m) deep hole in the ground before a crowd of onlookers, who were addressed by Michigan governor William Milliken."

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