Followed by the experimental subjects. Researchers want to know whether water-soluble dietary fiber can improve metabolic diseases while losing weight. So they chose T5KO mice without TLR5 gene. Because of the lack of this gene, it will cause intestinal flora disorder and metabolic diseases.
Speaking of which, explain it again.
When a baby is born, the intestine is sterile. With eating, bacteria begin to settle in the intestine. Then, the running-in began. Bacteria can stimulate the immune system and promote its development. On the contrary, the immune system will choose bacteria, so everyone's intestinal flora is different.
For example, bacteria are like vendors, intestines are streets, and immune cells are urban management. Without vendors, it is inconvenient to buy things, and too many vendors disobey management, which will also cause inconvenience to the people. In the process of management, enthusiastic citizens need to participate. For the human body, enthusiastic citizens are the TLR5 gene, which is responsible for identifying the flora in the intestine and judging whether to make a report call (activating the MYD88 pathway). [4]
The next step is the experiment.
The first step of the experiment is to feed the mice with food rich in inulin (accounting for 7.5% of the total diet). As a result, the mice did lose weight. However, serological examination shows that bilirubin in mice is abnormal, which usually indicates abnormal liver function. Therefore, the researchers continued to feed, and they were surprised to find that after six months, 40% of the mice had liver cancer.
Inulin is mentioned here. Inulin is a soluble substance extracted from chicory root, that is to say, from the source, inulin belongs to the second category, which is artificially extracted and enriched, and from the physical properties, inulin belongs to water-soluble dietary fiber.
Subsequently, the researchers did two experiments. One is to study other mice. The results showed that some mice from other species also developed liver cancer, but mice lacking MYD88 did not. This shows that intestinal flora imbalance is inextricably linked with liver cancer.
Finally, the researchers tried to control the intestinal flora of mice, such as killing the intestinal flora of mice with antibiotics, and the mice were fine no matter how they were fed inulin.
So, what should we ordinary people think of this research?
First of all, some scholars have determined the dietary fiber in daily food. The results show that natural dietary fiber is mainly insoluble (IDF), while soluble (SDF) is much less. [5]
Contents and types of dietary fiber in common foods [5]
Secondly, this study conflicts with previous studies. Inulin has a long history of use, and its safety is rarely questioned in previous literature. [6]
Even if you eat, the average person can't eat that much. It is estimated that Europeans consume 3~ 1 1 g inulin on average every day. [6]
According to the Dietary Guidelines for China Residents, if all the oil, salt and meat are added together, you can eat at most 182 1g food a day. I want to replicate the experimental results with human body. Dietary fiber accounts for 7.5%, namely 137g. Studies have shown that eating more than 80g of dietary fiber every day can cause abdominal distension. This is an impossible task.
Inulin intake in Europe and North America [6]
Dietary Pagoda (Source: Dietary Guide for China Residents, 20 16)
What's more, mice without TLR5 gene suffer from liver cancer, and mice without MYD88 do not, which fully shows that the key lies in the products of inulin fermentation and decomposition, which affect the intestinal flora, and the immune system plays an important role in it, so the experimental conclusions cannot be copied to normal people.
Finally, we should not only look at the disadvantages, but also look at the benefits. A large number of studies have confirmed that dietary fiber is beneficial to health, and has the functions of losing weight, improving metabolism and reducing the incidence of cancer. [7]
For example, a 20-year follow-up study showed that eating enough dietary fiber in early adulthood can significantly reduce the incidence of breast cancer. [8]
The Nutrition Society of China advises people to consume 25-30g dietary fiber every day, but previous surveys show that residents' intake is not up to standard in both urban and rural areas. [2]
Investigation on dietary fiber intake [2]
In fact, in the interview, the author mentioned that inulin used in the experiment is not a natural food, but is proposed and processed by chemical means; Their purpose is not simply to blame water-soluble fiber, but to hope that people realize that foods with additional dietary fiber may not be as good as fruits and vegetables. [9]
In a word, the significance of this experiment is that if you keep a high-fat and high-sugar diet and expect to maintain your weight through extra dietary fiber, it may not be worth the candle.
The correct way is to refer to reliable books such as Dietary Guide for China Residents and analyze their own dietary patterns. If the dietary fiber intake is insufficient, you should eat more celery, leeks and oats. , completely change their living habits.
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refer to
[1] Singer V, Yang Benshan, Chasien B, et al. Dys regulates cholestatic liver cancer induced by microbial fermentation of soluble fiber [J]. Cell, 20 18, 175 (3): 679-694. E22。
[2] China Nutrition Society. Reference Intake of Dietary Nutrients for China Residents (Version 20 13) [M]. Science press, 20 14.
[3] Soluble fiber and insoluble fiber: different physiological reactions. [J]。 Food science and technology, 1987.
Wang Chunfeng. Interaction between intestinal microorganisms and immune system [J]. Journal of Jilin Agricultural University, 2018,40 (4): 475479.
Yin,, people. Determination of dietary fiber in different foods [J]. Health Research, 2004,33 (3): 331333.
Cousement PAAA. Inulin and fructooligosaccharides: safe intake and legal status [J]. Journal of Nutrition, 1999,129 (7):1412s-1.
[7] McCrorey J.W. Evidence-based methods of fiber supplements and clinical health benefits, part 1 part [J]. Nutrition today, 2015,50 (2): 8289.
Zhang Zhiyong, Wang Xiaohong, et al. Relationship between dietary fiber and breast cancer [J]. Pediatrics, 20 16, 137 (3): E20 15 1226.
[9] It is found that adding refined fiber to processed food may have a negative impact on health. Science Daily, [20 18- 10-22]. . The signed articles published on this website only represent the author's views and have nothing to do with this website. If there is any infringement, you are responsible.
Author: Zhao Yanchang