Is the “Five-Second Rule” Safe?

Do you know what the “five second rule” is?

The five second rule is the widely accepted notion that it’s OK to scoop up food that has fallen on the floor as long as you do it within a “safe” five-second window.

But is there any truth to this dogma?

Rutgers’s university professor and extension specialist in food science Donald Schaffner wanted to find out. So here’s what he did.

He took the bacteria Enterobacter aerogenes and applied it to stainless steel, tile, wood, and carpet. He let the surfaces dry for five hours and then dropped some watermelon, bread, bread with butter, and gummy candy on the contaminated surfaces. He allowed them to come into contact with the surfaces for less than a second, five seconds, 30 seconds, and five minutes. Then, he cultured the various foods for the bacteria.

Here’s what he found:

The food with the most contamination was the watermelon. And the food with the least contamination was the gummy candy. According to Schaffner, we shouldn’t be surprised by this. “Transfer of bacteria from surfaces to food appears to be affected most by moisture,” he said. “Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer.”

One thing was surprising, though. The surface with the lowest contamination was the carpet. Hard surfaces like tile and steel had much higher rates of contamination, with wood surfaces somewhat variable. The smoother the surface, the faster the bacteria transfer onto the food.

So how about contact times? Did the five second rule hold up?

The study discovered, not surprisingly, that the longer the food was in contact with the contaminated surface, the more bacteria were transferred to it. So, in this sense, the rule held up.

However, when everything is just right, when the food is wet and the surfaces are smooth, contamination can happen in less than five seconds. In some cases, it was even less than one second.

Yours for better health,

Frank Shallenberger, MD