Fibre in the diet – the key to healthy digestion

Dietary fibre has long been one of the key elements in assessing the quality of a diet, although the concept itself is relatively recent. The term ‘dietary fibre’ first appeared in scientific literature in 1953. Over time, the definition of fibre has been expanded, as it turned out to encompass several different groups of compounds with varying properties. Today, its importance is considered primarily in the context of proper bowel function, the digestion of nutrients and the quality of the overall diet.

1. Characteristics of fibre
2. The effect of fibre on the digestive tract
3. A high-fibre diet
4. FAQ – frequently asked questions about dietary fibre

Characteristics of fibre

Dietary fibre is a group of substances, mainly of plant origin, which the human body does not digest or utilise in the same way as starch (a type of complex carbohydrate) or simple sugars (e.g. glucose). These consist primarily of various types of carbohydrates that are not broken down by digestive enzymes in the small intestine, as well as lignin associated with plant cell walls. As a result, a significant proportion of the fibre reaches the large intestine.

Fibre includes, amongst other things, cellulose, hemicelluloses, pectins, beta-glucans, gums and certain types of resistant starch. Individual types differ in their solubility in water, viscosity and susceptibility to fermentation by gut bacteria. Some fibre binds water and increases the volume of intestinal contents, some may increase its viscosity, whilst certain fractions are utilised by microorganisms present in the large intestine. A single food product usually provides several fractions at once.

Good sources of fibre include wholegrains, oat flakes, bran, groats, pulses, vegetables, fruit, nuts and seeds. Whole grains generally contain more fibre than products made from highly refined flour, and whole fruits provide more fibre than juices with the pulp removed.

The effect of fibre on the digestive tract

The best-documented area of fibre’s effect is its impact on bowel function. The European Food Safety Authority (EFSA) has determined that a daily intake of 25 g of fibre is sufficient to ensure normal bowel function in adults. This figure was established, amongst other things, on the basis of data relating to bowel movements, stool consistency and transit time through the gut.

Authorised health claims also apply to specific types of fibre. Fibre from wheat bran contributes to an increase in stool bulk, and consumption of at least 10 g of this fraction per day allows the claim that it contributes to accelerating intestinal transit. For rye fibre, a claim is permitted stating that it contributes to normal bowel function. Fibre from oats and barley, on the other hand, may be described as contributing to an increase in stool bulk, provided the product meets specific conditions regarding fibre content.

Fibre content in selected products

A high-fibre diet

A high-fibre diet is best based on minimally processed foods. Sweet and savoury snacks, as well as most fast-food dishes, should be avoided.

Throughout the day, it is a good idea to combine wholegrain cereals, vegetables, fruit, pulses, nuts and seeds, as these provide different types of fibre. If your fibre intake has been low up to now, it is best to increase the amount of fibre in your diet gradually. A sudden switch from a diet low in plant-based foods to one very rich in bran, pulses and whole grains may cause temporary digestive discomfort. Importantly, as your fibre intake increases, you should also ensure you drink enough fluids.

You can replace some of your white bread, rice or pasta with wholegrain versions, eat vegetables regularly, choose whole fruits instead of juices, and include pulses according to your individual tolerance. It is better to spread your fibre intake across several meals rather than consuming most of it in a single serving.

“Whilst it is important to ensure you get enough fibre, bear in mind that it is not advisable to increase your intake suddenly. If you have been eating very little fibre up to now, start improving your diet, but do so gradually. You will avoid bloating and wind, and your body will be able to adjust to the change in its own time.” Agata Bugorska – IFAA Trainer

FAQ – frequently asked questions about dietary fibre

How much fibre should you eat each day?

The European Food Safety Authority (EFSA) considers 25 g of fibre a day to be the appropriate amount for healthy bowel function in adults. However, this does not mean you need to meticulously count every gram. Regular consumption of whole grains, vegetables, fruit, pulses, nuts and seeds helps.

What’s the easiest way to increase the amount of fibre in your diet?

You can start with a few simple changes: choose wholemeal bread instead of white, eat more groats and porridge, eat whole fruits instead of juices, and regularly include vegetables and pulses in your meals. It’s best to increase your fibre intake gradually.

Is it possible to eat too much fibre?

A very high amount of fibre, particularly if introduced suddenly, can cause bloating, wind, a feeling of fullness and other digestive complaints. More isn’t always better – individual tolerance also matters.

Why does bloating occur when you increase your fibre intake?

Certain types of fibre are fermented by gut microorganisms. A sudden increase in fibre intake can therefore lead to increased gas production. It is a good idea to give your body time to adjust to the change in diet.

Do you need to drink more on a high-fibre diet?

It is important to ensure an adequate intake of fluids, especially when increasing the amount of high-fibre foods. Some types of fibre bind water, which is why staying hydrated is a key part of a high-fibre diet.

Which contains more fibre – fruit or juice?

Usually, the whole fruit does. Juicing and removing the pulp results in the loss of a significant portion of the fibre. For example, an orange provides around 2.4 g of fibre per 100 g, whilst orange juice provides around 0.2 g per 100 g.

Do wholegrain products really contain more fibre?

Usually, yes. According to the data provided in the article, wholemeal wheat flour contains around 10.6–12.2 g of fibre per 100 g, whilst white flour contains around 2.7–3 g. This is one of the reasons why replacing some refined cereal products with wholegrain ones makes it easier to increase fibre intake.

Does fibre help with constipation?

The effect depends, amongst other things, on the type of fibre. The EFSA states that fibre from wheat bran helps to increase stool bulk and, when consumed in adequate amounts, may also help to speed up intestinal transit. However, not every cause of constipation is linked to insufficient fibre intake.

Sources:

• Balk, E. M., Couch, E., Mai, H. J., Chen, Y., Adam, G. P., Kanaan, G., Caputo, E. L., Trikalinos, T. A., Williams, G., Duncanson, K., Talley, N. J., & Lichtenstein, A. H. (2026). Fiber intake and laxation in people with normal bowel function: a systematic review. The American journal of clinical nutrition, 123(3), 101212. https://doi.org/10.1016/j.ajcnut.2026.101212
• Makki, K., Deehan, E. C., Walter, J., & Bäckhed, F. (2018). The Impact of Dietary Fiber on Gut Microbiota in Host Health and Disease. Cell host & microbe, 23(6), 705–715. https://doi.org/10.1016/j.chom.2018.05.012
• de Vries, J., Birkett, A., Hulshof, T., Verbeke, K., & Gibes, K. (2016). Effects of Cereal, Fruit and Vegetable Fibers on Human Fecal Weight and Transit Time: A Comprehensive Review of Intervention Trials. Nutrients, 8(3), 130. https://doi.org/10.3390/nu8030130