The science behind the ‘5 second rule’

We must have all had that devastating moment, when you are holding the most tantalising piece of food in your hand, then in slow motion the precious morsel slips out of your grip and tumbles on to the floor. Absolutely heartbreaking stuff, until of course somebody comforts you with three magical words – 5 second rule – and you realise this food is still fit for consumption. It is still OK to eat right?? Right??

Believe it or not people have researched whether there is truth in this rule, and the results may actually surprise you.

The research:

The logic behind this rule is that germs from the floor wouldn’t have enough time get all up in your food in just 5 seconds, so the food should be fine if you pick it up quickly. The research tested the rule based on this idea, and placed items of food on floors covered in bacteria for varying amounts of time and then measured how much bacteria had got into the food.

The results:

The less time food was on the floor, the less bacteria was able to transfer in to the food – which shows living by the 5 second rule isn’t a bad idea.

However, what did matter even more was the amount of bacteria on the floor to begin with, if your floor is infested with crap, the bacteria will likely get into your food, even if you do pick it up fairly quickly – but you would have to drop the food in that exact spot where the bacteria is for this to be a problem.

They also found that you can add more time on to the 5 second rule if the food is dropped on carpet. Bacteria transferred to food much slower on carpet compared to wood or tiles. This means if you drop food on the carpet it is likely to be safe – it just might be a bit furry.

Why does toast always drop butter side down?

Whilst on the topic of dropping food, I thought I would try and find an answer to why toast pretty much always falls butter side down. In most situations when we drop toast we knock it off a kitchen counter or a dining table, and the ‘knocking off’ motion as well as the difference in drag between the side with butter on (no air holes) and the plain side (loads of air holes) tends to give the toast some rotation in it’s flight to the floor. But, because our kitchen units, dining tables and sofas aren’t that tall, the toast can only manage about half of its rotation before it hits the floor, and a half rotation usually results in the toast flipping just enough so the butter side is facing the floor, absolutely gutting stuff. Apparently if you drop toast from a bigger height it will have less chance of falling butter side down as it will be able to complete the rotation before meeting the floor.

So there you have it, 5 second rule is a-ok, particularly with carpet. I have once again answered one of life’s big questions using science – you can thank me with a cheeky retweet or follow.

Till next time,




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