According to the news, according to the findings of scientists at Harvard Medical School in the United States, if the environment is too clean and hygienic, it is easy to accidentally develop autoimmune diseases such as asthma and inflammatory bowel disease. The study was published in the journal Science[1].
Therefore, this sounds like a fulfillment of the old saying "no dry and clean eating is not sick".
Is this really the case?
Not all bacteria are harmful,
But some bacteria are really powerful
There are actually many bacteria living on the surface and intestines of the human body, and the total number of these bacteria is ten times the number of cells in the human body. So if every bacterium and every cell has the same voting power, then each of us is a walking "bacterial body."
It is precisely because the vast majority of bacteria are harmless to the human body that humans can be at peace with intestinal bacteria and have the opportunity to evolve to today.
However, most bacteria are fine, which does not mean "not dry and clean, eat no disease". If the human body encounters bacteria that are more harmful, the consequences will be very serious.
Many plagues that often appeared in ancient times were caused by bacteria. For example, the "Black Death" that prevailed in medieval Europe caused a 1/3 reduction in the European population, and in some Italian cities, the death toll even reached 80%. Today's DNA archaeological findings of medieval European remains have caused the Black Death by Y. pestis, although the species at that time were different from those of modern Plague bacillus [2].
In the face of plague bacilli, do you dare to "not dry and clean, eat no disease"?
Only those who have not seen the plague dare to utter such ignorant and fearless words. In the face of the Black Death that did not know where it came from, the people of the Middle Ages not only did not dare to say "not dry and impure, eat no disease", I am afraid that they did not even dare to look at it. Is there any evidence? In Italy at that time, doctors needed to be fully armed to see patients, not only wearing a robe and a mask with a large bird's beak, but also stuffing the bird's mouth with herbs that were said to prevent diseases.
(Pictured: Beaky, a Roman physician.) By Paul Fürst, 1721)
The masks worn by doctors were later widely spread, and of course, the shape was no longer limited to the beaks of the birds like gas masks, but various masks that could be worn at the masquerade, in order to avoid the death from seeing the face. Centuries later, the black death finally passed, but mask making became an industry in Italy, and now when you travel to Venice, you can see beautifully made masks everywhere in the streets.
(Pictured: Masks everywhere in Venice, Italy.) Image source: Station Cool Helo)
The "Black Death" and plague are rare nowadays because the invention of antibiotics in modern medicine can very well control diseases caused by bacteria.
However, even in today's era of antibiotics, the harmful bacteria are not gone. As recently as March this year, salmonella infections broke out in 42 U.S. states because turkey meat was contaminated, infecting as many as 358 people, of whom 133 were hospitalized and 1 died. Such "turkey contamination" is not a rare event, and salmonella outbreaks are actually more common.
According to estimates by the U.S. Centers for Disease Control (CDC), 1.2 million people in the United States are infected with Salmonella each year, of which 1 million are transmitted through food. After the infection, patients will experience abdominal pain, diarrhea, fever and other symptoms, although in most cases, the condition will be relieved after 4-7 days, but every year 23,000 people go to the hospital, 450 people die as a result.
In the face of Salmonella, do you dare to "not dry and clean, eat no disease"?
In salmonella infections caused by turkey meat, patients are either caused by eating raw turkey meat or by exposure to raw meat with pathogenic bacteria before eating. In addition to undercooked food being contaminated with bacteria, many lifestyle habits and lifestyles are also prone to germs. For example, the latest outbreak of Salmonella infection in the United States has been traced to pet turtles at the source, because 71% of the patients surveyed have been exposed to this animal.
(Pictured: Pet turtle that brings Salmonella.) Image source: Station Cool Helo)
In this regard, CDC has given advice to prevent Salmonella and other pathogenic bacteria: wash your hands well! After touching raw meat or playing with your pet turtle, wash your hands thoroughly with soap.
In addition, CDC also recommends that pet turtles should not be kept in the kitchen or in a place where food is stored, so that animals do not bring germs to the food. If you need to clean the containers or toys for your pets, it is also best to do it outdoors and avoid operating in the kitchen to avoid germs falling into the food. As for kissing or intimate contact with pet turtles, that is more dangerous action, be careful.
Many bacteria may not have an acute hazard, but they also have a chronic effect on health
Obviously, human history has not always been epidemic with plague bacillus, and there is not always news of salmonella contamination in today's life, so is it not necessary to pay special attention to hygiene when there is no large-scale epidemic, and you can eat something that is not clean and unclean?
The main ways in which bacteria invade the human body are the respiratory tract, the digestive tract and broken skin. Normally, because humans have to eat every day, bacteria enter the esophagus and stomach with food. However, because of stomach acid in the stomach, a large number of bacteria will be killed, and only a small part of them can enter the intestine to multiply. A small number of pathogenic bacteria that enter the human blood circulation through the intestinal wall can also be controlled by the body's immune cells.
But the immune system can't stand the "bacterial" sea tactics of pathogenic bacteria. When the body's immunity is low, bacterial infections are more likely to occur. What kind of people are immunocompromised? Children under 5 years of age and adults over 65 years of age. If there is such a person in the family, special attention needs to be paid to hygiene, and it is best not to keep pet turtles that will bring pathogenic bacteria.
In ancient times, when there were no antibiotics, even without wars and plague epidemics, the average life expectancy of people was not long, and one of the reasons was related to various diseases caused by bacteria. Not only is it because of acute bacterial infections caused by wounds and contaminated food that can lead to death, but when a person's immunity declines in old age, even if it is a chronic infection, the body will not be able to bear it.
Bacterial infections are also linked to cancer. Helicobacter pylori is one of the carcinogenic factors of gastric cancer, and the nitrite products produced by the metabolism of various bacteria are also carcinogens. Before the 1930s, stomach cancer had the highest mortality rate in the United States. With the improvement of sanitary conditions and the invention of the refrigerator, the situation of food spoilage caused by the multiplication of bacteria has been greatly reduced, and the need for preservatives added to food has also decreased, so the incidence and mortality of gastric cancer have dropped greatly, and the incidence of stomach cancer in the United States is only 4 cases per 100,000 people, which is an uncommon cancer.
It can be seen that if the health hazards that bacterial infections may bring to health are completely ignored, "not dry and clean, eat no disease", bacteria-related diseases will explode. Although we still have antibiotics, drug-resistant bacteria have become a growing problem today because of the misuse of antibiotics, and once the sanitary conditions deteriorate, it means that more antibiotics need to be used to control bacteria, which will further accelerate the resistance of bacteria. If the extremely harmful drug-resistant superbugs become popular, the catastrophe of modern society will come, and humanity will return to the Middle Ages overnight.
Even if there is no catastrophe, human health will be threatened. The continuous increase in life expectancy is a sign of social progress. If "it is not dry, it is not sick to eat", and the health environment deteriorates, then the average life expectancy will take a turn.
How to understand the conclusions of the Science paper?
Since sanitation is important to human health, how do we understand the conclusions of the current Science paper?
This study is mainly an animal test, a study of a certain pathogenic mechanism. In both humans and mice, there is an "invariant natural killer T cells" (iNKT). In an overly clean environment, iNKT is too much enriched in tissues, and once exposed to a causative agent, this iNKT can lead to serious pathological damage, inducing autoimmune diseases such as asthma and inflammatory bowel disease [1].
In the face of this study, we should first note that the focus of this study is actually the problem of "excessive hygiene". The experiment compared the mice's two living environments, one sterile and one normal. But there is a fungal environment here, in fact, the sanitary conditions are still very good. According to the normal requirements of the experimental animal room, not only does someone need to clean the cage and clean the mouse on time, but also have certain regulations on the temperature and light of the room, and the feed of the mouse must also meet the requirements of nutrition and hygiene, so this so-called "bacteriological environment" is not the environment where wild mice on the street are wandering around, nor is it the environment in which rats that spread the plague live. Mice living in such experimental animal houses, although still in a fungal environment, have a much longer natural lifespan than rats on the street.
Secondly, we should also realize that in such a "worry-free" environment, asthma and other diseases that occur in mice are not actually fatal diseases, but chronic diseases that can be controlled by drugs.
The findings were published in 2012. Later, epidemiological investigations of humans also found a link between "excessive hygiene" and asthma. In the United States, there are some special descendants of German-Swiss immigrants, some of whom live in Pennsylvania and other places, called Amish people, live a simple traditional rural life, and even refuse modern facilities such as cars and electricity in their daily lives; there are also some people, called Huters, who also live in the countryside like the Amish people, but do not reject modern facilities, so it is a modern rural life. The survey found that the incidence of asthma in children was very different in the two groups with relatively close genetics: hutres were 4 times higher than those of Amish! [3]
Further investigation found that there were more bacteria in the homes of the Amish people who lived a traditional rural life. If bacteria collected from amish homes are put into the nasal cavity of mice, it can suppress the over-the-top immune response of the respiratory tract. From this result, it seems that the bacteria in the amish people's living environment can help them reduce immune diseases such as asthma.
We can actually summarize a more objective understanding by taking these results together: good hygiene habits are definitely needed, which is a matter of survival; but on this basis, do not pursue sterility too much, that is, there is no need to have "cleanliness". In order to get better health, you should actually be exposed to more beneficial bacteria (probiotics).
This is not at all "not dry, not clean, eat no disease".
Of course, there is also a need for a correct understanding of probiotics. Probiotics are just a name that includes a variety of different strains. The bacteria in Amish's house can suppress the excessive immune response of the respiratory tract, which is not the same as eating a probiotic and achieving the same effect. And one thing is crucial: whether probiotics have any benefits or not requires rigorous evidence. For example, the above-mentioned bacteria from Amish's family, although they have proved a certain function in mice, but whether humans have the same function, this also requires experimental evidence.
There is no need to rush to pay for "Amish bacteria" to prevent asthma before getting the evidence, but you can take your children to the village where the Amish people live.
(Pictured: Amish people in the United States who still live a traditional agricultural life.) Image source: Station Cool Helo)
I believe that "not dry and unclean, eat no disease" can take you to the ditch; correct understanding of probiotics can avoid being routine.
bibliography
[1] Olszak T, An D, Zeissig S, VeraMP, Richter J, et al. (2012) Microbial exposure during early life haspersistent effects on natural killer T cell function. Science336:489-493.
[2] Haensch S, Bianucci R,Signoli M, Rajerison M, Schultz M, et al. (2010) Distinct clones of Yersiniapestis caused the black death. PLoS pathogens 6:e1001134-e1001134.
[3] Stein MM, Hrusch CL,Gozdz J, Igartua C, Pivniouk V, et al. (2016) Innate Immunity and Asthma Riskin Amish and Hutterite Farm Children. N Engl J Med 375:411-421.
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