Simple sugars from fruits, plant fibers and fiber must always be included in our diet. As proven by research by scientists from the USA, Denmark and Australia, presented at the 15th International Immunological Congress in Milan, they affect the composition of the intestinal microflora, and this in turn – on our immune system, making us less sick. The presence of plant fibers in the diet is important, especially in diabetes.
From Milan for MedOnet Marek Mejssner
Caring for the good condition of the digestive tract, and especially the bacteria it contains, is very important – explained the research of Prof. Gabriela Nunez, from the University of Michigan. Nunez addressed a rarely studied problem of the mechanism of gastrointestinal colonization by common bacterial pathogens. These pathogens are bacteria that grow in water or food. They are not invasive, so they do not damage the intestinal epithelium. However, they settle in the digestive tract, causing chronic inflammation of the colon. These are: the haemorrhagic Escherichia coli (EHEC), the enteropathogenic Escherichia coli (EPEC) and the rodent Citrobacter rodentium.
Gut bacteria fight pathogens
Prof. Nunez investigated the mechanism of infection in humans using the latter bacteria and a special type of mice, free from bacterial flora. These mice, obtained through special breeding procedures, do not have their own bacterial flora of the digestive tract and the course of infection in the digestive system is examined on them. The scientist found that bacterial pathogens have a special area in the genome that facilitates their colonization of the intestinal epithelium. It is activated early in the infection and begins to produce proteins that help bacteria to colonize the intestinal epithelium over the intestinal mucus area. However, at a later stage, the expression of these genes begins to decline, i.e. proteins that allow them to settle in a specific place are no longer produced and the bacteria tries to settle on the surface of the gastrointestinal tract. The next phase is very important because it is filmed there, which is a thin layer of normal intestinal bacteria, characteristic of every human being.
In 2012, it was the team from the University of Michigan led by prof. Nunez proved that the composition of the intestinal flora is different and unique in every human being, like a fingerprint. These differences are minor and seemingly insignificant, but in fact they determine your health. With a good biofilm condition with bacteria, they will be able to compete effectively with pathogens and remove them from the gastrointestinal tract on their own, without any outside help. If, on the other hand, they are weakened, the fight can be difficult and its outcome uncertain, which means repeated bowel ailments, even leading to inflammation. Both commensal bacteria and pathogens must compete for the same amount of carbohydrates in the food digested in the intestine.
The development of commensal (natural) bacteria is favored by, inter alia, providing them with appropriate carbohydrates not from sweets but from fruit. Only these are able to digest, and the complex sugars found in sweets perfectly serve pathogens and small colonies of fungi living in the intestines. Similarly, they are supported by fiber, e.g. from vegetables, oatmeal and rye, as well as from dark bread and bran, while starch from light wheat bread hinders the action. Nor do they benefit from too much protein from excess meat in the diet.
Healthy plant sugars
The problem of the presence of dietary fibers and carbohydrates in the diet was dealt with by a team of scientists from Denmark, working under the supervision of prof. Hanne Frokiar from Kobenhavns Universitet. Plant fibers are a necessary element of the diet, positively influencing the commensal flora of the digestive tract, similarly to dietary carbohydrates. To see what this effect looks like, scientists added 10 percent. xylooligosaccharide (XOS), a simple plant sugar, in the diet of mice. Tests proved that this supplement had a positive effect on the development of a significant part of the gastrointestinal flora – Bifidobacterium. After the blood was collected, it turned out that the state of the immune system improved. As you can see, simple plant sugars serve the bacterial flora and at the same time support the immune system, reducing the risk of inflammation caused by infections.
Plant fibers help with diabetes
In turn, an Australian team of scientists led by Dr. Eliana Marino from Monash University in Melboune investigated the role of the gastrointestinal flora in one of the most dangerous and common autoimmune diseases – type 1 diabetes.
Currently, type 1 diabetes accounts for about 8-9 percent. all people with diabetes. The problem is significant because there are approximately 200 people with diabetes worldwide. Type 000 is most common among children, adolescents and people under 000 (up to 1%), although it can also occur later. However, clinicians argue that the very onset of the disease rarely occurs after the age of 30. The number of cases has been growing since the mid-90s and now type 15 diabetes is becoming a problem not only in the USA and Western Europe, but also in Central European countries, e.g. in Poland.
Researchers from Monash University in their research dealt with the important problem which is the dependence of the diet on the appearance of the disease and its progress. A poor diet in adolescence, with lots of junk food, and obesity are mentioned as important risk factors in this type of diabetes. Australian researchers looked at the problem of diet after an illness and its impact on bacteria in the digestive tract. It is known that the bacterial flora of the gastrointestinal tract is a modulator of the immune system, regulating the immune response to threats, i.e. locally and at the level of the entire human organism, it affects its functioning.
Until now, the problem of the dependence of the diet and gastrointestinal microflora on the immune system has not been thoroughly researched – the cellular pathways that would accurately identify these dependencies are not fully known. Meanwhile, researchers at Monash University found, children with type 1 diabetes have an altered immune system in the intestines and their increased permeability. One of the reasons for this may be the nutritional system that led to type 1 diabetes mellitus due to its lack of plant-based dietary fibers, which interferes with the normal process of immune tolerance.
Scientists studied this process using the NOD (non-obese diabetic) mouse. They serve as a model for insulin-dependent diabetes research because they have the spontaneous ability to develop insulin-dependent diabetes. As found in the experiments, the high amount of plant-based dietary fiber in their diet reduced the risk of diabetes. Then, SCFA short-chain fatty acids were produced – the important role of which for the immune system was emphasized by the research of the Danish team – and they were linked by the GPR43 receptor for G proteins. These are very important proteins that occur in the cell membrane and transmit signals inside the cell. The smaller the amount of plant dietary fibers, the more the composition of the gastrointestinal bacterial flora changed in an unfavorable direction, the amount of SCFA decreased and the relationship with the GPR43 receptor was broken, and the mice developed diabetes. As you can see, nutrition in this disease is very important.
Tekst: Marek Mejssner