We've all dropped food on the floor and picked it up to eat before. Is it because of the 5 second rule? How good and accurate is this rule?

A new study out of Manchester Metropolitan University has come up with a more nuanced iteration of the fallen food rule. If you're going to pick up foods from the floor, you better know which ones are safer.

Researchers looked at five test foods, bread with jam, cooked pasta, a slice of ham and a plain cookie and a dried fruit. They were left on the floor for intervals of three, five and 10 seconds. These foods were selected because of their variance in water activity level, water being the factor for bacteria growth.

And here's what they found:

• Foods with a high salt or sugar content, were less likely to pick up harmful bacteria in so short a period of time. The ham (high salt) and sugary bread and jam were both considered safe, with little sign of bacterial growth. The jam's high sugar content made the slathered slice inhospitable for bacterial growth.

• The cooked pasta and dried fruit, however, both tested positive for klebsiella, a bacteria known to cause a range of diseases and infections, as well as soft-tissue conditions. Unlike ham, the salt in it protects the meat from growth of most bacteria.

• The dry cookie was also relatively well off—after three, five and ten seconds—because of its low water activity level and "adhesion ability".

So if you're going to pick food that you dropped on the floor the next time round, make sure its processed, or packaged foods. Because the sugarier and saltier they are, the better.

[DailyMail via Foodbeast]