The Sacramento Bee reports that indeed, the five-second rule is part guilty habit, part old-wives’ tale — a popular conviction that food is still clean if snatched off the ground within five seconds.
Yet, it should come as no surprise that the tale turns out to be exactly that — a not-so-legitimate justification for diving after the last cookie.

“I’m not a believer in the five-second rule,” said Chuck Gerba, a professor of environmental microbiology at the University of Arizona. “I never know what was on the floor before me.”
Well, it’s true that it’s a gross, gross world out there, and even a superficial delving into the details is enough to make the most phobia-phobic person bust out the antibacterial hand soap.
For instance, your cutting board contains 200 times more bacteria than your toilet, Gerba said. Your sink? A porcelain E. coli farm. And don’t even get him started on that dish sponge.
“You’re giving the germs a free ride around the home,” Gerba said.
Hmm. Maybe that five-second rule isn’t such a good idea, after all.
A few years ago, an ambitious high-school student named Jillian Clarke actually put the rule to the test during a seven-week internship at the University of Illinois.
There, in the laboratory, Clarke — who for her efforts later won an Ig Nobel Prize (given by the science humor journal Annals of Improbable Research) — disproved the famous — or more accurately, infamous — rule by finding that food had a significant amount of bacteria on it after less than five seconds on floors that had been purposely contaminated.
Even so, Clarke’s first experiments — on the actual floor of the lab — revealed a much cleaner surface than expected. Fans of the five-second rule note: Your loophole may start here.
Meanwhile, just last year, “Mythbusters,” the Discovery Channel television show that takes famous myths to task, also took on the five-second rule after getting hundreds of requests from folks inquiring about its veracity.
“This myth has been popping up for a long time,” said Eric Haven, associate producer of the show. “I think a lot of people have the experience of dropping something on the floor and (then) someone will eat it.”
For the report, the “Mythbusters” crew dropped food on various surfaces, rubbed the items on a petri-dish-like plate, then put it in an incubator. A lab was tapped to analyze it. The findings?
“There are levels of bacteria on every surface of every house and every home,” Haven said. “There are low levels of things that in high quantities are quite nasty.”
The team also found that the drier the food item, the less yucky stuff it picks up. Which, translated, means cookie, probably OK, and lunch meat, most probably not OK.
Like many folks, Heather Bermudez, 29, knows the five-second rule by its alias, the three-second rule. But, whether it’s three, five or 700 seconds, the Elk Grove mom and professed germ freak said she’s leaving that food right where it fell.
“If it hits the ground, it’s dirty,” she said.
Of course, her toddler does not hold the same view.
Though there’s been a surprising amount of research into the truth of the rule, little is known about its origins. Who started it? And when did we add those extra two seconds?
Well, no one really knows, but it’s thought by some that we owe the beginnings of the five-second rule to Genghis Khan — though he himself was said to have allowed a generous half a day on the floor. Guess it’s true what they say about things being much slower back then.
So, it would seem that the moral of the rule is: It’s all subjective. Don’t fool yourself into believing it’s true — but hey, it’s not that much worse than what you’re touching every day.
But do everyone a favor: Keep it to yourself when you double-dip.