Fibre

Beginner · 10 min

The undigested carbohydrate

Fibre is technically a carbohydrate, but human digestive enzymes cannot break it down; most of it travels all the way to the large intestine. Its energy contribution is therefore low: in label calculations fibre is usually valued at about 2 kcal per gram, and in some systems it is not counted at all. Fibre's value lies not in the energy it carries but in the work it does along the digestive tract.

Fibre is shown on its own line on labels; when comparing two similar products, that line is as informative as the sugars line. Products carrying 6 grams of fibre or more per 100 grams are usually good options within their category. Because the line is not mandatory in every country, some labels may not carry it.

Soluble and insoluble fibre

Soluble fibre forms a gel-like structure in water; oats, apples, legumes and linseed are typical sources. It slows stomach emptying, extends fullness, and some types are reported to have a favourable effect on blood lipids. Insoluble fibre does not dissolve in water; it is found in whole grains, bran and the structure of many vegetables. It regulates bowel movements and adds bulk. Most fibre-rich foods carry both types together, so in practice aiming for variety is enough; there is no need to memorise types.

The distinction between the two types is more a tendency than a strict classification; the proportions in the same food can vary even with the variety and the cooking method.

Fullness and gut health

Fibre-rich foods generally require more chewing, keep the stomach occupied longer, and provide more volume for the same energy; that is where their contribution to fullness comes from. Part of the fibre also serves as food for the beneficial bacteria in the large intestine; these bacteria ferment fibre and produce compounds used by gut cells. The relationship between gut health and overall health is an active research area; treating unconfirmed claims with caution while acknowledging the established benefits of fibre-rich eating is the balanced position.

A side effect of fibre-rich meals is that they slow down eating: the longer the chewing, the better the brain's chance of catching the fullness signals. Taking the same energy more slowly means, for most people, stopping earlier.

How much, and how

For adults, a frequently cited reference is roughly 25-30 grams of fibre a day; many people's actual intake falls below this range. The sources are well known: vegetables, fruit, dried legumes, whole grains, nuts. When increasing intake, two principles matter: gradual transition and enough water. Raising fibre abruptly can cause bloating and gas; an increase spread over a few weeks, with plenty of water, makes it easier for the digestive system to adapt.

Eating peelable fruit with its skin, swapping white rice for bulgur now and then, and adding legumes to soups: three small examples that raise fibre intake without it being noticed.