Five-second rule
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The five-second rule is a popular North American old wives' tale about eating food that's been dropped on the floor.
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The rule
The rule states that foods—particularly sweet foods like cookies—that have fallen to the ground will not contract any germs until five seconds have passed. The rule provides a convenient rationale for eating food off the floor, and is usually invoked when a group of people are present (as a polite fiction). Thus, for example, a person might drop a dry jelly bean, pick it up quickly, tell his friends "five second rule" and then eat the candy.
The five-second rule is seldom invoked in the case of sticky foods, such as ice cream or jelly beans which have been moistened, particularly if visibly dirty. The origin of the five-second rule is unknown.
In reality, it is usually safe to eat food from a relatively clean floor (see "Research" below). However, the notion that germs from a dirty floor will not reach food for at least five seconds is false. For this purpose, cleanliness is a matter of bacterial contamination rather than visible dirt, although the two often go together. For example, sick people attend hospitals, with the result that a hospital floor which has not been decontaminated properly can appear to be relatively clean, while actually being more contaminated than the dirty street outside.
No data exists for the use of the five-second rule in restaurant kitchens; nonetheless, the practice is thought to enjoy a frequent use by cooks in a hurry. Although the idea of the five-second rule being used in fine dining establishments as an official policy is absurd, its use is not limited to restaurants of lower standards.
Variations
The five second rule is sometimes called the three-second rule, 10-second rule, or the 15-second rule, to some extent depending on locale, the quality of the food involved or the intoxication level of the individual quoting the rule. For example, in American college dormitories the ten-second rule is often quoted as the "drunk version" of the five-second rule. In addition, there is the 17-minute rule, a humourous observation that the transferrence of dirt and germs takes place regardless of how short a time the food is in contact with the ground.
It is also widely believed that, in the home, the five-second rule can be extended to at most 15 seconds. In public places and restaurants, however, the amount of time is generally shortened.
Idioms
There are a number of idiomatic expressions used around the world when eating food which is in some way perceived as dirty or hazardous. Some examples:
- O que não mata, engorda (Brazil: "if it doesn't kill you, it's fattening").
- Lo que no mata, engorda (Spanish-speaking countries: "if it doesn't kill you, it's fattening").
- Chancho limpio nunca engorda (Spanish speaking countries: ("A clean pig never gets fat").
- Dreck macht Speck (Southern Germany: "Dirt makes bacon").
- Lite skit rensar magen (Swedish: 'Some dirt cleans the stomach').
- Zand schuurt de maag (Dutch: "Sand cleans the stomach").
Research
A study on the five-second rule was performed by Jillian Clarke, a high school senior, during a seven-week internship at the University of Illinois in 2003. Clarke and a doctoral candidate named Meredith Agle took swab samples from various floors around campus. They then looked at the samples under a microscope and discovered that they did not contain significant amounts of bacteria. The conclusion was that in most cases, dry floors would be safe to eat from.
However, Clarke also wanted to test the five-second hypothesis in cases where the floor was known to be contaminated. She therefore spread E. coli on both rough and smooth floor tiles in a laboratory, placed pieces of gummy bears and cookies on the tiles for various amounts of time, and then examined the foods under the microscope. All the foods had a significant amount of bacteria after less than five seconds. Her findings therefore disproved the five-second rule.
In the course of her research, Clarke also conducted a survey to sample opinion on the five-second rule. She found that seventy percent of women and fifty-six percent of men were familiar with the five-second rule, and most utilized the rule in their decisions to eat food that had fallen on the floor. She also found that women were more likely than men to use the rule, and that cookies and candy were more likely to be picked up than broccoli or cauliflower.
Clarke's work won an Ig Nobel Prize for Public Health in 2004.
The five-second rule was also featured in an episode of the Discovery Channel series MythBusters. The results they got from their tests confirmed Clarke’s findings: time was not a factor when food is exposed to bacteria, even two seconds' exposure is more than enough time to contaminate it.