Probiotics "harmful"?

"Probiotics" is a word with strong emotional tendency. Probiotics, that is, things that are beneficial to life, make people like it at first sight. Dairy products that we often drink often use "probiotics" as propaganda words to package the health care efficacy of the products.

However, recently, two papers published in the top international journal Cell questioned the role of probiotics, arguing that probiotics are not as beneficial to the human body as we thought, and even interfere with the original microorganisms in the intestine.

Through a series of experiments in human intestine, researchers found that some people's digestive tract will hinder the colonization of probiotics.

They also found that it is generally believed that probiotic supplements are helpful to restore intestinal flora after antibiotic treatment, but it is unreasonable that probiotic supplements will delay the return of intestinal microorganisms and intestinal gene expression to normal.

The seventh note of the diatonic scale.

Figure | Cell magazine published two studies on the influence of probiotics on intestinal microbial community (title: probiotics destroy the reconstruction of intestinal mucosal microbial tissue after using antibiotics, but autologous fecal microbial transplantation can promote reconstruction; The colonization of conventional probiotics in intestinal mucosa is related to the characteristics of host microbiota (source: Cell)

On the one hand, it is the propaganda of manufacturers, on the other hand, it is the research of scholars. Who do we listen to?

First, let's take a look. What are probiotics?

1906, Henry Tisser, a French pediatrician, found that there was a Y-type bacterium in the feces of children with diarrhea, and its number was lower than that of normal children.

So Dissel thought, since there are few Y-type bacteria in patients, we should add some Y-type bacteria or stimulate Y-type bacteria through some substances to alleviate or even disappear the symptoms of patients.

Half a century later, some scholars finally confirmed Dissel's conjecture, calling extra live bacteria or substances that stimulate the reproduction of inherent bacteria in human body probiotics, which is just the opposite of antibiotics. [ 1]

Y-shaped bacteria, namely Bifidobacterium (image source: en.wikipedia.org)

The meaning of "probiotics" we are talking about today is relatively narrow, especially the live bacteria that can produce health care after reaching a certain amount. [2]

Secondly, what are the probiotics?

Probiotic products can be roughly divided into two categories, one is medicine, which we don't often touch, and the other is food.

If you buy a box of yogurt casually, there must be Lactobacillus bulgaricus and Streptococcus thermophilus in the ingredients marked on the package, which is necessary for yogurt production. It is because of them that yogurt has a unique sweet and sour taste and sticky taste. Both of these bacteria are probiotics.

So probiotics are not uncommon. It is estimated that 70% probiotics are used in food, including yogurt, cheese, milk powder, soybean milk, candy, juice and ice cream. [3]

So are probiotics beneficial?

In theory, probiotics are beneficial.

When a baby is born, the intestines are clean. With activities such as eating, bacteria will gradually appear in the intestine.

On the one hand, these bacteria participate in substance metabolism and assist in the digestion and transportation of sugar, lipid and protein. On the other hand, it can stimulate the immune system and fight and kill alien invasive bacteria by seizing territory and nutrients. This is a normal flora, which is of great significance to maintaining health.

Normal flora is certainly not a kind of bacteria, but includes many kinds of bacteria. At present, probiotics approved in China can be found in normal flora. If probiotics can stand in the intestine, it will not only make people have a healthier digestive system, but also make people have a more effective immune system.

But in fact, to achieve this effect, we must first establish a normal flora model; Then analyze everyone's intestinal flora; Then, a sufficient number of purified specific bacteria are sent to their bodies; Finally, it is necessary to regularly check the colonization of bacteria.

This is very unrealistic.

There are two research directions in reality. Highly purified pharmaceutical-grade probiotic products are used for patients. The results show that probiotics have obvious effect on treating infantile diarrhea and antibiotic diarrhea.

Another thing we are most concerned about is the impact of foods containing probiotics on ordinary people.

For ordinary people, there are three levels from theory to reality.

First, the problem of strains.

Normal flora includes many kinds of bacteria, and it is not easy for someone to guess which bacteria need to be supplemented. What is more troublesome is that even the same bacteria will have different performances. Some scholars have studied 42 strains of Lactobacillus plantarum. The results show that although they can induce monocytes to secrete immune substances, the secretion amount is 14 times different. [2]

Second, the issue of quantity.

As mentioned earlier, the intestines of ordinary people contain a large number of bacteria. The Specification for Declaration and Evaluation of Probiotic Health Food (Trial) stipulates that the number of live bacteria in live probiotic health food shall not be less than 106 cfu/mL (total number of colonies /mL) during its shelf life. [2]

Even if this number is reached, it is still a problem whether the intestine can colonize successfully in the face of many bacteria inherent in the intestine.

Previously, some scholars analyzed the published studies, and the results showed that only 1 of the seven randomized trials showed signs of successful customization of probiotics. [4]

One of the papers mentioned in this media report also reached a similar conclusion, and whether probiotics can colonize or not depends on the characteristics of different people, and the colonization effect is far less than expected. [5]

The third question, our previous "beneficial" conclusion, is based on the assumption that "probiotics will join the normal flora and assist the normal flora". Is there any other possibility?

The paper mentioned in another media report focuses on this point. Scholars used antibiotics to interfere with the intestinal flora of volunteers, and then divided them into three groups.

One group let it recover naturally, one group took probiotics, and the other group extracted some bacteria from the intestine in advance and then implanted them in volunteers again.

The results show that probiotics can interfere with the recovery of normal flora for up to 6 months. [6]

Based on these studies, we can infer that bacteria in normal flora are not harmonious and unchangeable. Every kind of bacteria will be affected by internal and external factors, and will try their best to obtain more living resources, and you will gain more and more, and you will retreat and achieve a relatively stable situation in the game.

Therefore, foreign live bacteria are not easy to join; However, once it is interfered by antibiotics and other factors, foreign strains will seize the opportunity and the recovery of normal flora will be affected.

Seeing this, some friends will definitely ask, after all, can I still drink yogurt?

For specific patients, such as children with diarrhea and patients with antibiotic diarrhea, there is more evidence that probiotics can relieve symptoms, and there is no reason not to continue using them until more research appears.

For other patients, such as those with low immunity and intestinal mucosal defects, studies have shown that probiotics can transform themselves into invasive bacteria, causing infection and bacteremia, and should not be used. [8]

If you are a healthy person, it is basically useless to hope to gain extra benefits such as losing weight and relaxing bowels through probiotics.

Of course, if you just like the taste of yogurt, drink it. As mentioned above, as long as the normal flora is complete and undisturbed. Then foreign bacteria (whether probiotics or invasive bacteria) may not make any waves.

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refer to

[1] Zheng Yuejie of Huang Zhihua. Correct understanding, evaluation and use of probiotic drugs [J]. China Journal of Practical Pediatrics, 20 1 1.

[2]HILL C, GUARNER F, REID G, etc. Expert consensus document: consensus statement of the International Association for Science on the scope and methods of probability and ecology. Proper use of the word probiotics [J]. Review of gastroenterology and nature. Liver disease, 20 14,11(8): 506514.

Du Peng, Huo Guicheng. Development Status of Probiotic Products at Home and Abroad [J]. Food Science, 2004,25 (5):194198.

Kristensen B, BRYRUP T, ALLIN K H, et al. Changes of fecal microbial composition caused by experimental supplements in healthy adults: a systematic review of randomized controlled T. Materials [J]. Genome Medicine, 2016,8 (1): 52.

Zmoran, ZILBERMAN-SCHAPIRA G, SUEZ J, et al. Individualized intestinal mucosal colonization resistance to empirical probability is related to unique host and microbial characteristics [j]. Cell, 20 18,174 (6):1388-/.

[6]SUEZ J, ZMORA N, ZILBERMAN-SCHAPIRA G et al. Microbial reconstruction of intestinal mucosa after antibiotics was introduced by Probiology and improved by autologous FMT [J]. Cell, 20 18,174 (6):1406-/kloc.

[7] Dr. Mike R. Probiotics [J]. Canadian Family Physician, 2005,51(11):14551457.

[8]FIJAN S, FIJAN S. Microbes claiming probiotic properties: a review of recent literature [J]. International Journal of Environmental Research and Public Health, 20 14,1(5): 47454767.

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Author: Zhao Yanchang