Junk science: The 5-second rule

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The 5-second rule is not mentioned here, but still shows that going against Mother Nature leads to convoluted and wishful thinking. Found here.

You remember this. It’s where a child says that if you drop food on the floor and pick it up in less than five seconds, you can safely eat it again. Many adults believe it too. It is hard to know where these ideas come from.

There was a V-Sauce video on the 5-second rule made back in Noveber of 2012, that debunks it with everyday science. V-Sauce mentions, however, that your immune system protects you from a good deal of the bacteria that are sure to come from the floor. There is a MythBusters episode on TV that debunked the 5-second rule also. But away from popular science, there is also a 2007 article in The Journal of Applied Microbiology that not only do microbes adhere to food pretty much on contact, but further that, on an otherwise clean, dry tile floor, Salmonella typhimurium can survive for over a month in large enough numbers to pose a human health problem (40 days, according to the journal). S. typhimurium is a bacteria known to cause typhoid fever in humans.

In scientific terms, “clean” is taken to mean “free of dirt and debris”. Only “sterile” can mean “free of all bacteria and other single-celled organisms”. The floor in this case would be clean but not sterile, just like a floor would be in any average well-kept home.

Well, that was back in 2007, and there has since been another journal article released two days ago by researchers at Rutgers University (who published in the journal Applied and Environmental Microbiology), with what appears to be bigger samples with more surfaces and more measurements than ever before. The lesson, however, is still the same: if food falls on the floor, the safest way to deal with the food is to just throw it out.

Sterility is too lofty a goal for an average home, requiring the inside of the home to be sealed off and air-tight, and for the people entering the home to cover their clothes with a sterile outer suit (since they are contaminated from being outside), and to put on shoe and hair coverings before entering the house.

Eating in a sterile environment

Eating and getting rid of bodily wastes would require, as the easiest solution, to do all that outside the house. Once food is brought into the home, any hope of sterility is gone. Growing food in the home does not absolve you from microbes, since most plants and animals need bacteria to grow. And you don’t just need the individual microbes, you need the whole ecosystem they belong in. Past attempts at building artificial ecosystems isolated from the rest of the world had all ended in failure. To get rid of bodily wastes, you would need to build an outhouse — one with running water, if you like to be fancy. None of these are the most comfortable solution to everyday needs which we take for granted.

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I am Paul King, a math and science teacher. I help maintain the MIT FAQ Archive along with Nick Bolach. I am also the maintainer of the FAQ for sci.bio.food-science.