Two studies explain why dietary fiber is so valuable to health
A diet rich in dietary fiber, such as that provided by fruits and vegetables, reduces the risk of developing diabetes, cardiovascular disease, and arthritis, (1) and more generally reduces the risk of premature death, as found in a meta-analysis published in 2015 in the
American Journal of Epidemiology
.
If the usefulness of consuming fiber-at least 25 grams per day, according to Efsa – is known, less known is the mechanism that makes it beneficial to health. Two studies published in Cell Host and Microbe. One is conducted by researchers at the University of Gothenburg in Sweden, the other is the work of teams led by Andrew T. Gewirtz of Georgia State University.
The virtuous mechanism triggered by dietary fiber
Dietary fiber does not act directly on the body, the two studies explain, but nourishes millions of active bacteria in the gut. The meal wastes released by them in the form of short-chain fatty acids in turn feed intestinal cells, which produce more mucus-the insulator needed to protect the intestinal walls from attack by pathogenic bacteria-and emit antibacterial molecules. Consequently, if there is a lack of fiber in the diet, the bacterial population is reduced (the microbiota), it thins the protective mucus that keeps pathogenic bacteria away and alerts the immune system. The alarm activates an inflammatory process that can become chronic and extend from the gut to the entire body.
The effects of fiber on guinea pigs
The two researches tested the effects of a diet with or without dietary fiber (also administered with inulin supplementation) on mice. In guinea pigs used by U.S. scientists, a diet high in fat and low in fiber reduced the intestinal bacterial population by 10 times. In those followed by the Swedish team, switching from a high-fiber diet to a low-fiber diet disrupted the mice’s microbiota. Many common bacterial species have become rare, and rare ones have become common.
In addition to changes in the microbiota, both teams observed rapid changes in mice. Dietary fiber deficiency has resulted in a thinning of the intestinal mucus layer. As a result, the bacteria got too close to the intestinal wall, triggering an immune reaction, which became chronic within days. After a few weeks, the mice began to accumulate fat and develop higher blood sugar levels.
Notes
(1) High consumption of fruits, especially berries, yellow vegetables, green leafy vegetables, and cruciferous vegetables (cauliflower, kale, cabbage, broccoli, Brussels sprouts, savoy cabbage, and the other types of cabbage) or their fibers is associated with a reduced risk of developing the type 2 diabetes, concluded the meta-analysis published in June 2015 in the Journal of Diabetes Investigation.
Also in 2015, a meta-analysis published in
Clinical Nutrition
showed that dietary fiber consumption is inversely associated with the risk of
coronary artery disease
, particularly for fiber from grains and fruits. In addition, soluble and insoluble fibers have a similar effect. A significant dose-response relationship between fiber intake and coronary heart disease risk is also observed.
Another study published in 2017 in Rheumatic Diseases on the other hand, has shown that high fiber consumption is beneficial in both reducing body weight (see recent study in The American Journal of Clinical Nutrition), both to reduce the inflammations, benefit theosteoarthritis Of the knee.
Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".
