If you have sneakily picked up food that's fallen on the floor and popped it in your mouth, here's what you need to know.

The idea that food is not contaminated if it is retrieved quickly has been believed for many years - but there has not been extensive proof that this is the case. Now though, the doubt is out as scientists have finally investigated the theory to discover whether the rule is fact or fiction.

Eating processed food from the floor poses the lowest risk - one of its few benefits - given that it generally contains such high levels of sugar and salt.