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If you like to eat whole-grain bread and eat five portions of fruit and vegetables a day, you have a good chance of consuming enough dietary fiber: At least 30 grams a day, recommends the German Society for Nutrition. Studies show plant fiber has a positive effect. High fiber consumption thus reduces the risk of colon cancer, diabetes or cardiovascular disease. And: patients with rheumatoid arthritis also seem to benefit from it.
By: Antje Maly-Samiralow
Dietary fiber is unfairly denigrated as ballast. Yet they are very healthy and belong on the table every day, whether as vegetables, whole grain bread or in the form of legumes.
Dietary fiber in vegetables, fruits, legumes
The collective term dietary fiber includes food fibers that cannot be digested by the human digestive system and are largely excreted. Dietary fiber is found exclusively in plant foods, primarily in vegetables, fruits, seeds and nuts, legumes and cereals – especially in the outer layers of the cereal grains.
This is where the term "dietary fiber" comes from, because the outer layers of the grain were considered indigestible and therefore useless dietary fiber, which was sifted out during milling. The result was fine, light flours, without husks and coarse grains, which made bread and pastries appear more noble.
History of dietary fiber
In the past, people in our latitudes generally ate more grains in the form of porridge, soup, groats and, of course, bread. Before flour began to be finely sieved, these foods were rich in dietary fiber. 100 years ago, the daily consumption of dietary fiber was around 80 grams per day. Today, the average dietary fiber intake is only about 20 grams, although the Germans still do well internationally because many people in this country eat muesli for breakfast and also eat significantly more whole-grain bread than in other industrialized countries.
In the seventies of the last century dietary fibers were seen in a different light again. Surveys of the health status and dietary habits of people from the African continent, who traditionally eat a diet rich in natural fiber, led to the thesis that a low-fiber diet, as is the norm in industrialized countries, can result in a whole range of diseases.
"Our organism depends on dietary fiber. If these are lacking, civilization diseases such as rheumatoid arthritis or diabetes are imminent."
Recommendation: 30 grams of dietary fiber per day
Conversely, a high intake of dietary fiber can reduce the risk of a whole host of diseases and conditions, among others:
– cardiovascular diseases – some cancers (especially colon cancer) – diverticula – hemorrhoids – constipation
Both the WHO and the German Nutrition Society recommend a daily intake of at least 30 grams of dietary fiber, half of which should come from cereal products.
Good against intestinal diseases
Especially patients with intestinal diseases benefit from a diet high in dietary fiber. The gastroenterologist Prof. Dr. Martina Muller-Schilling, for example, recommends a high-fiber diet to reduce the risk of developing colorectal cancer. This applies to both at-risk patients with pre-existing conditions and healthy individuals.
"Dietary fiber protects against colon cancer. Because they cause our food mush to pass through the intestine more quickly. This means that potentially harmful substances cannot act on the mucous membrane long enough and thus our intestinal mucosa is protected."
But dietary fiber exerts even more health-promoting effects in the gut.
"Dietary fiber maintains good intestinal flora. And they promote the production of immune modulators, which ensure a healthy immune system."
Dietary fiber reduces the risk of diabetes
A high consumption of dietary fiber also reduces the risk of diabetes. The nutritionist Prof. Hans Hauner investigates which dietary fibers can most effectively regulate the rise in blood sugar levels.
"Normally, the food pulp enters the stomach, remains there for a while, is acidified, and then enters the small intestine. There, the food is broken down, and when sugar is then released, it is absorbed into the bloodstream. Dietary fiber can have a very strong influence on this – delaying it – and can then contribute to the fact that, for example, blood sugar rises much more slowly after a meal containing bread. We want to take advantage of this, both to prevent diabetes and to treat it when it has already broken out."
Prof. Dr. med. Hans Hauner, director of the Else Kroner Fresenius center for nourishing medicine, TU Munich
Dietary fiber in convenience foods
In an interdisciplinary research project, Prof. Hauner on how to make low-fiber convenience foods so they contain more fiber and still taste good.
"It would be ideal, of course, to consume dietary fiber through natural foods, such as fruits, vegetables, and whole grains. But only a few people do this. That's why we've made more popular foods like pizzas, liverwurst rolls here in Bavaria, or even muffins healthier by adding dietary fiber and making them taste just as good. We have let test persons try the fiber-enriched food, and they could not determine a difference."
Prof. Dr. med. Hans Hauner, spokesman and coordinator of the research network, enable nutrition cluster
Good against autoimmune diseases and allergies?
At the University of Nuremberg-Erlangen, scientist Mario Zaiss is investigating whether dietary fiber influences the development and course of autoimmune diseases, and if so, by what mechanisms. In a recent study, he has patients suffering from rheumatoid arthritis consume 30 grams of dietary fiber in the form of bars or a granule-like cereal. The aim is to find out whether the inflammatory reactions associated with rheumatic diseases can be reduced by dietary fiber.
"In our preliminary experiments, we found that a high-fiber diet alleviates autoimmune diseases because it regulates the overactive immune system and thus reduces inflammation."
Dr. med. habil. Dr. rer. nat. Mario Zaiss, Erlangen University Hospital
In another study, he investigates the influence dietary fiber can have on allergies, especially dust allergies.
Which foods contain a particularly large amount of dietary fiber??
Data in each case per 100 grams of the foods mentioned
Generally found in whole-grain products such as whole-grain bread, whole-grain pasta, and brown rice, as well as in legumes, nuts, fruits, and vegetables.
Daily consumption of dietary fiber
In order to achieve a minimum daily intake of 30 grams of dietary fiber, the German Nutrition Society recommends the following food selection, for example:
Drink a lot against flatulence
Prof. Dr. Martina Muller-Schilling also recommends that patients slowly accustom their digestive tract to dietary fiber. This applies in particular to legumes, which can cause flatulence. Who reacts with belly ache and bloating to an increased fiber supply, the appropriate food should reduce first and increase the dose then gradually. Also, drink plenty of fluids when adding more fiber to your meal plan.
"It is important to drink a lot, at least two liters a day, so that the fiber can swell and you do not get constipated."
Prof. Dr. med. Martina Muller-Schilling, Director of the Clinic and Polyclinic for Internal Medicine I, University Hospital Regensburg
The swelling behavior and the ability to absorb larger amounts of water are one reason for the digestive effect of dietary fiber. This increases stool volume and stimulates intestinal peristalsis, resulting in faster intestinal transit. However, in order for dietary fiber to swell, it needs to be adequately hydrated.