Fiber and its importance on the diet

Any food we eat is broke down into small molecules to then be absorbed into our body.

This process is called digestion, it begins in the mouth and it ends in the small intestine where the majority of the absorption of the nutrients takes part.

Fiber are the edible parts of plant based carbohydrates which are resistant to digestion and absorption.

It turns out that our body does not have enzymes to break down the fiber, they reach out to the small intestine intact and because of the slow transit time, the “friendly” bacteria present in our gut ferment the fiber.The product of this fermentation are biochemicals that benefit friendly bacteria suiting as a source of energy and favorably the Ph.

Many types of fiber are them considered PREBIOTICS due to the fact that:

Resists gastric acidity, hydrolysis by mammalian enzymes, and absorption in the upper gastrointestinal tract;

Is fermented by the intestinal microflora;

Selectively stimulates the growth and/or activity of intestinal bacteria potentially associated with health and well-being.

Although all prebiotics are fiber, not all fiber is prebiotic.

Prebiotics occur naturally in foods such as leeks, asparagus, chicory, Jerusalem artichokes, garlic, onions, wheat, oats, and soybeans.

In addition to function as a prebiotic, since fiber can not be absorbed, it carries out with it a portion of molecules of fat, carbohydrates and protein into the stool, which helps to control blood sugar, blood cholesterol and blood protein levels ( lower some risk factors for cardiovascular disease and diabetes among others).

Moreover, fiber reaching out the large intestine nearly “untouched” it increases the weight of the stool by the physical presence of the fiber, water held by the fiber, and increased bacterial mass from fermentation.

Larger and softer stools increase the ease of defecation by increasing the area in contact with the intestine’s wall that in turn stimulates the contraction of it (peristalsis).

It also reduces transit time through the intestinal tract, which may help to prevent or relieve constipation, reducing the risk for colon cancer.

In adults, the recommended amounts of dietary fiber range from 25 to 38 grams/day. In children, recommended amounts vary according to the energy requirements of different age groups.

Although the recommendations can be met through a diet rich in vegetables, nuts, seeds, fruit and whole grains, according to a Ireland National Adult Nutrition Survey 2008 – 2010, adults are not eating enough fiber.

Fiber is considered an essential nutrient and an increase on its consumption is crucial for promoting health.

Some of the benefits from a high fiber diets come naturally from the non dietary fiber compounds such as naturally oxidants and pytochemicals.

The role of fiber in health depends on characteristics such as solubility, fermentability, and viscosity, hence the necessity to consume fiber from a variety of sources.

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Dietary Fiber, The European Comssion’s Science and Knowlodge. Avaiable at

Fiber and Prebiotics: Mechanisms and Health Benefits, Slavin J., Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, MN 55344, USA. Avaiable at

Handbook of Dietary Fiber, Cho S. S., Dreher L. M., 1st Ed, Dec 2019.

The Dietitian Kitchen- Nutrition for a Healthy, Strong & Happy You, Major K., Meyer and Meyer Sport Ltda, 2020

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