Unravelling the role of dietary fibre: benefits, sources and guidelines for optimal consumption

Fibres are plant fibres that are resistant to the enzymes of the human digestive system. In fact, they are indigestible carbohydrates that make up the cell walls of plants. Unlike other carbohydrates, which are broken down into easily digestible sugar molecules, dietary fibre passes through the intestinal tract relatively unchanged.

A growing body of evidence suggests that adequate fibre intake can help improve digestion and reduce the risk of chronic disease. Many of these benefits are due to our gut microbiota – the millions of bacteria that live in our digestive system. They outnumber cells in the rest of the body by 10 to 1.

While bacteria live on the skin, in the mouth and in the nose, the vast majority of bacteria live in the gut, mainly in the colon [1]. Once in the colon, dietary fibre is broken down by these beneficial bacteria, which also produce acetic and butyric acids to maintain the acid balance of the digestive system.

Unraveling Dietary Fibre's Roles: Benefits, Sources, and Guidelines for Optimal Consumption
Illustration by slegtaseta.net

It is important to get enough fibre in your diet as it helps maintain healthy digestion, control weight, regulate blood sugar levels and more. It has also been linked to longevity and a reduced risk of cancer. Fibre refers to the indigestible parts of plant foods.

According to the Dietary Guidelines for Americans [2], men aged 50 years and younger should consume about 38g of fibre per day, and up to 30g over the age of 50. Women under 50 should get about 25g, and women over 50 should get up to 21g. However, the average intake of fibre by Americans is only 15g per day.

What types of fibre are there?

There are two main types of fibre: soluble and insoluble. Each has its own specific properties and affects the human body in different ways.

Once in the body, insoluble fibre mainly retains its shape and speeds up the removal of food from the stomach and the emptying of the bowels by swelling in water. It also helps to eliminate bile acids and cholesterol, prevents constipation and normalises metabolism.

Soluble fibre dissolves in water to form a gel-like substance. It coats the stomach and makes you feel full. However, it doesn’t provide significant energy as it contains minimal calories.

Most plant foods contain both soluble and insoluble fibre, but the amount of each varies from food to food.

Foods rich in soluble fibre include:
  • Beans
  • Lentils
  • Oatmeal
  • Peas
  • Citrus fruits
  • Blueberries
  • Apples
  • Barley
Foods rich in insoluble fibre include:
  • Wholemeal flour products
  • Wheat bran
  • Brown rice
  • Cauliflower
  • Potatoes
  • Tomatoes
  • Cucumbers

Some foods, such as nuts and carrots, are excellent sources of both types of fibre.

Unraveling Dietary Fibre's Roles: Benefits, Sources, and Guidelines for Optimal Consumption
Illustration by slegtaseta.net

What are the benefits of fibre?

Consuming fibre benefits all organs and systems in the body. This is an undeniable fact recognised by mainstream medicine. Regular inclusion of fibre in the diet helps maintain normal intestinal microflora, prevents the development or worsening of diabetes, significantly reduces the risk of cardiovascular disease, normalises liver and gallbladder function, removes heavy metals, radionuclides and toxins from the body, and acts as a powerful preventive measure against cancer, especially colon cancer.

Fibre is often referred to as a life-giving fibre. In fact, this almost vitamin-free and calorie-free substance contributes to the overall recovery of the body. Fibre provides vital energy, strengthens the immune system, regulates metabolic processes and stabilises weight at a level that is comfortable for the individual. It’s been proven that a lack of dietary fibre can lead to hypertension, obesity, dysbiosis, gastritis and more than thirty other serious diseases.

Healthy digestion

Fibre is known to improve digestion by increasing the volume and regularity of stools. Bulkier and softer stools are easier to pass than hard or watery ones, improving comfort and promoting bowel health.

Increasing fibre intake can also have a positive effect on bowel health. A study published in the journal mSystems [3] found that increasing fibre intake for two weeks can significantly alter the gut microbiome, including increasing the number of microbial species that help break down fibre.

Heart health

Fibre also helps to lower cholesterol levels. The digestive process requires bile acids, which are partly made from cholesterol. As digestion improves, the liver pulls cholesterol out of the blood to make more bile acids, reducing LDL (bad) cholesterol levels. Medical research suggests that eating 16g of fibre a day can reduce the risk of heart disease by 70%.

Blood sugar regulation

Consuming fibre, especially soluble fibre, slows down the digestion of carbohydrates and the subsequent release of glucose into the bloodstream. This regulation helps to prevent blood sugar spikes, which is essential for people with diabetes or those at risk. People with diabetes should consistently include fibre-rich foods in their daily diet.

Possible cancer prevention

Fibre has been shown to bind and remove toxins from the body that contribute to the development of cancer. Fibre binds between 10 and 50% of nitrosamines and other harmful compounds with carcinogenic properties.

Normalising liver and gallbladder function

As mentioned above, fibre reduces the reabsorption of cholesterol. The same is true of bile acids. This action normalises liver and gallbladder function and prevents the onset of gallstone disease.


Some research suggests that fibre may contribute to a longer life. A meta-analysis of studies published in the American Journal of Epidemiology [4] suggests that high fibre intake may reduce the overall risk of death.

Unraveling Dietary Fibre's Roles: Benefits, Sources, and Guidelines for Optimal Consumption
Illustration by slegtaseta.net

Switching to a high-fibre diet

To reap the full benefits of fibre, many people adopt a high-fibre diet. According to the University of Michigan guidelines, it’s best to start gradually when adding more fibre to your diet. Consider adding 5g of fibre a day for two weeks. Too much fibre too quickly can lead to bloating, cramps and even diarrhoea. It’s important to give your body time to adjust to the increased fibre intake.

The University of Michigan also recommends balancing your intake of caffeine-free and caffeinated beverages. Because caffeine acts as a diuretic, causing fluid loss, excessive caffeine combined with a high-fibre diet can lead to constipation. Ideally, you should aim to drink two cups of decaffeinated drinks for every cup of caffeinated drink.


Fibre is generally considered safe and has few contraindications. It is recommended for everyone, including children, adults and the elderly. However, it’s important not to introduce fibre-rich foods too early in the diet of young children. The appropriate time to introduce fibre-rich foods to a child should be determined by a paediatrician who’s familiar with the child’s health history. Fibre intake should be limited during flare-ups of gastric and duodenal ulcers. However, it’s not necessary to exclude fibre from the diet during periods of remission.

It’s advisable to avoid fibre-rich foods during episodes of diarrhoea, which can be caused by conditions such as poisoning, dysentery, dysbiosis or other diseases. Until bowel movements return to normal, it’s wise to limit fibre intake.

Prepared by Mary Clair

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