Is dirt edible

immune system: How much dirt is healthy?

Four thousand six hundred. That's how many types of microorganisms the geologist Helge Trond Torsvik found in a gram of forest soil that he had examined using DNA sequence analysis. That is several million bacteria, viruses, algae, fungi and protozoa. And not all are bad for humans. Mycobacterium vaccae for example - vaccae , Latin for "from the cow" - was first found in cow dung and could act as an antidepressant. The oncologist Mary O'Brien discovered this by chance when she administered the bacterium to cancer patients. Although it did not slow down tumor growth as hoped, the patients with the cow bacterium rated their quality of life better than that of a control group. So dirt can be good for people. No wonder, since its body contains more bacteria than its own cells. He also makes a lot of dirt himself, after all, house dust consists to a large extent of people, namely, dander.

So dirt is a matter of definition, "matter in the wrong place", as Brecht wrote. With the boom of the Masters Proppers and Sagrotans in the 20th century, the place to be for most Western Europeans is: in nature. Everything in the house should not only be clean, but also clean. Whether that is a good thing has been doubted since 1989. Then the epidemologist David Strachan formulated his hygiene hypothesis. This says that the enormous increase in allergies in the industrialized nations since the 1950s can be explained by the constantly improving hygiene conditions. With the decline in infectious diseases, the variety of microorganisms that had surrounded humans for centuries decreased. The immune system, especially that of children, gets out of balance and reacts exaggeratedly to actually harmless things such as pollen, mites, grasses. Almost every fifth German now suffers from an allergic disease.

Several studies agree with Strachan: Children who come into contact with dirt more often and who, for example, grow up among their peers in the day care center throwing bacilli, with wormy pets or, best of all, on a farm between the cowshed and pitchfork, have fewer allergies and asthma than those who grow up comparatively germ-free Children. Most recently, a long-term study showed that even a few grams of dirt can be beneficial to health: 1,037 participants in the study were surveyed who chewed their dirty fingernails or sucked their thumbs in kindergarten. In allergy tests, which the study participants later had to undergo at the age of 13 and 30, it turned out: Overall, fewer thumbsuckers and nail picks had developed an allergy than those who did not have these habits as a child.

The five-second rule remains: Edible food that fell on the floor a few seconds ago can be eaten without hesitation. Researchers checked that. They say: bacteria don't care if you pick up food after three seconds or three days, they besiege it immediately. The decisive factor is which and how many bacteria are on the crash site, whether the edible is sticky or rather dry (bacteria prefer dry), whether the floor is smooth or carpet-like (bacteria love smooth surfaces). In a study, researchers stated: If there are fewer than 50 germs per square centimeter on the fallen food, it is probably still edible. The best thing to do is to get a microscope for such cases.

The sources for the ZEIT-Wissen article can be found here.