Five-second rule Posted Tuesday, October 04, 2005 10/04/2005 06:17:00 PM

So I recently was caught in a discussion about the five-second rule.  You know that rule that says if you drop a piece of food on the floor it is ok to eat if you pick it up within 5-seconds.  One person said that they thought the rule was disproved.  I disagreed and said that I thought the rule was proven correct by a high school student science experiment.  With such a disagreement there is only one thing to do… consult the all-knowing oracle or wisdom (that would be Google).  So I did the “research” and discovered that the 5-second rule was proven false… but yet true at the same time.

High school student Jillian Clarke studied the five-second rule as part of summer internship in the Department of Food Science and Human Nutrition at the University of Illinois at Urbana-Champaign.  Her study won an Ig Nobel Prize for Public Health in 2004.  In the most literal sense Clark’s study disproved the five-second rule.  Clark showed that foods dropped on intentionally pre-contaminated tiles (hard surfaces) were contaminated in less than five seconds.  It appears that five seconds has no bearing on the how contaminated the food will get.  If you drop your food on a contaminated floor it should not be eaten.

So this seams pretty straight forward… right?  Snopes marks this one as an urban myth.  But wait a minute!  They are missing a vital part of Ms. Clarks study.  The details above are from Ms. Clarks 2nd experiment where she intentionally pre-contaminating ceramic tiles with E. Coli, dropped various food products for various amounts of time, and then measured the E. Coli count on the food.   However, the first part of her experiment (details here and here) Ms. Clark and her team took swab samples of floors at various locations around her campus.  They showed that the bacteria levels where not high enough to cause significant contamination of your food product.  It is noted that this is more then likely due to the types of surfaces sampled.  They measured dry hard surfaces.  It is likely that soft damp surfaces will have higher bacterial counts.

So the literal sense the 5-second rule as it is stated is correct for some floors.  If food that falls on your kitchen floor sits for less then 5-seconds it is, most likely, ok to eat.  Matter of fact if the food is on the kitchen floor more then 5-miniutes it is probably ok to eat.  But nobody would suggest you apply this “rule” to food dropped on your damp doggy bed.  Besides what doesn’t kill you makes you stronger… right?