No More Five-Second Rule?

The five-second rule has become quite popular as well as an accepted norm in our daily lives. But is it actually true? Do bacteria really take blog-1more than five seconds to be transferred onto our dropped food? Surprisingly, there have been quite a few studies on this phenomena, and they have all mostly come to the conclusion that the five-second rule is not applicable in every scenario.

There is no debate on the fact that the longer the food is left on the ground, the more bacteria is transferred onto it. However, research shows that the rate at which bacteria is transferred is not uniform. The texture of both the foods and the surface that it has fallen on has an important role in determining the amount of bacteria that is being transferred.

A recent study conducted in 2016 itself took samples of different types of foods and surfaces and measured the amount of bacteria transferred over different time intervals. The study was conducted at Rutgers University and involved a data set of 2,560 measurements showing that the study’s conclusion can be trustworthy assuming that the experiment was carried out fairly. Unlike other studies, there were several X-Variables in the experiment. The researchers were manipulating the surface by interchanging between stainless steel, ceramic tile, wood and carpet, the food by interchanging between watermelon, bread, bread and butter, and gummy candy and the time by interchanging contact time from less than a second, five seconds, 30 seconds and 300 seconds. The bacteria used in the experiment were ones that occurred naturally in the human digestive system. The mixture of the variety of the types of surface, food and contact time lead to 128 possibilities. Each one was carried out 20 times. To minimize the effect of third confounding variables, the surfaces were allowed to dry completely before coming in contact with the food. All in all, the well-controlled environment and frequency of the number of times the experiment was conducted show that the researchers conducted a fair study.

The head researcher, Donald Schaffner explained the results of the study and identified a possible mechanism. He concluded that the food was contaminated at different rates and that all the causative variables along with factors like moisture were the reasons behind it. For example, the study showed that wetter foods experienced more contamination in comparison to dryer foods. The study also showed that the foods began being contaminated as soon as the food got in contact with the surface.

In conclusion, while the five-second rule may seem plausible in showing that the longer the food stays in contact with the surface the more contaminated it gets, it tends to ignore the fact that contamination starts as soon as contact is made. So the next time you hear the five-second rule being used make sure to look at the texture of the food and the surface it touches. You may just be satisfying your hunger with bacteria rather than food.


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Rutgers University. “Researchers debunk ‘five-second rule’: Eating food off the floor isn’t safe: Sometimes bacteria transfer in less than a second.” ScienceDaily. ScienceDaily, 9 September 2016.

Aston University. “Dropped your toast? Five-second food rule exists, new research suggests.” ScienceDaily. ScienceDaily, 10 March 2014.

4 thoughts on “No More Five-Second Rule?

  1. Abigail Louise Edwards

    Hi Hi!

    I agree with Dana that this totally brought me back to my younger days! Also that if I know the surface is clean, I will most likely eat that pice of popcorn or chip that I dropped. Althogu, how clean is it really? I am much more inclined to eat the food that I drop on my kitchen floor back home than the food that I drop on the floor in my dorm, but that is just becuase I assume my home is cleaner than my dorm, but I dont relaly know that.
    This link here ( actually tells us that its not as big of a deal as it seems. They say that with a healthy immune system, the bacteria picked up off the floor within 5 seconds, wont hurt you! It is still gross when thinking of the logistics, but overall it is just mind over matter!


  2. Anthony Mitchell

    Ah, the proverbial “5 Second Rule”! I was wondering if/when this would come up as a topic. Thanks for posting it Arunima. As I have thought in many instances, the best thing to do varies from situation to situation. Everything seems to be dependent upon the amount of bacteria that is on a given surface and how quickly that bacteria is able to spread from the surface to the food item that has fallen. In the case of completely unsanitary floors (i.e. carpet, damp carpet, dirt, etc.), food is more likely to gain more bacteria quicker than maybe mopped floor in a low traffic area. The food that falls also matters; for example, ice cream may not be the best to try and recover from the floor after it has fallen. Floors are generally clean (for the most part), but microorganisms and bacteria don’t need long to travel from the surface to the food item. These are just a few things to think about as we move forward with the discussion.

  3. Dana Corinne Pirrotta

    I think that it is so cute that you did a blog about the 5-second rule because it isn’t something that I have thought about since early elementary school. Here is a link to Kid’s Health.Org because your post made me think back to childhood where eating off the floor was normal. This website talks about the do’s and dont’s of floor eating. I will pretty much pick something off the ground right away and eat it if I know the surface it fell on was relatively clean, so we all follow the five second rule even if we don’t actively think of it when we do.
    I think that it is very interesting that you mention that different bacteria contaminate the food at different rates, especially depending on what kind of texture the food has. These all seem like third variables and I like that you fluidly identify them in your post. I honestly never really thought about how the texture of my food would affect what sort of bacteria would congregate on it, and the speed at which they would do it nonetheless. It would have been really cool if you identified what foods took how long to contaminate. For example, something mushy like peanut butter is contaminated quickly while something gummy like Swedish fish takes more time. How about something hard but porous, like cereal? What kinds of characteristic combinations would be more resistant to contamination? I think it would have been more interesting to add some more examples.

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