What is fibre?
Fibre is one of the rare components that dietary guidelines insist on even though it provides no energy. This indigestible type of carbohydrate plays a part in everything from the regular working of the digestive system to the feeling of fullness.
Short answer
Fibre is the group of plant carbohydrates that digestive enzymes cannot break down; pulses, wholegrains, vegetables and fruit are the main sources. About 25 grams a day is a widely used reference value for adults. When increasing fibre it is important to do so gradually and to raise water intake alongside it.
Indigestible but useful
Fibre is the shared name of the carbohydrates found in plant foods that cannot be digested in the small intestine. Although it does not turn into energy, it works all along the digestive tract: it increases stool bulk, regulates bowel movement and feeds the beneficial bacteria in the large intestine. The general framework around this particular member of the carbohydrate family is set out in the carbohydrate guide.
Soluble and insoluble fibre
Fibres are divided in two according to their relationship with water. Soluble fibre forms a gel-like structure in water and is found in oats, pulses, apples and citrus fruit; slowing digestion and contributing to fullness are its main features. Insoluble fibre does not dissolve in water; it is found in the outer layers of wholegrains, in vegetables and in fruit eaten with the skin, and is known for supporting bowel movement. Most fibre-rich foods contain both types, so eating from a variety of sources is enough and there is no need to keep track of the types.
How much fibre, and from which sources?
About 25 grams of fibre a day is a general reference for adults used by many bodies, including the European Food Safety Authority (EFSA); some guidelines give slightly higher ranges. For a rough idea: a portion of boiled lentils provides about 7–8 g, an apple with its skin about 4 g, two slices of wholemeal bread about 4–5 g and a portion of oats about 4 g. As you can see, the target is reached not with one food but with choices spread across the day, and pulse dishes are the strongest helpers here.
Increase gradually, and do not forget water
Doubling fibre intake in a single day can lead to bloating, wind and abdominal discomfort. It is better to spread the increase over a few weeks so that the digestive system can adapt: swapping white bread for wholemeal first, then adding a weekly pulse meal the following week, for example. Because fibre works together with water, water intake needs to rise as well; otherwise the extra fibre can make digestion harder rather than easier.
Reaching about 25 grams in a day: a sample spread
To make the target concrete, look at the fibre total of a sample day. This is not a diet plan but an illustration of how the amounts add up. Start the day at breakfast with a portion of porridge (about 4 g) and a pear (about 4–5 g); at lunch add a bowl of lentil soup (about 5–6 g) and two slices of wholemeal bread (about 4–5 g); then a handful of almonds as a snack (about 3 g) and a vegetable-rich dish in the evening (about 4–5 g). By the end of the day the total reaches roughly 25–28 grams, and no meal has required unusual effort. The point to note is this: there is no single fibre bomb, and the target is met by the sum of ordinary choices. Small substitutions such as wholemeal instead of white bread, whole fruit instead of juice, and bulgur instead of rice now and then raise the total without your noticing.
Seeing fibre on a label
Fibre may be shown on a separate line in the nutrition table; 3 g or more per 100 g forms the basis of claims such as “source of fibre”, and 6 g or more of “high in fibre”. In products that give the impression of being wholemeal, it is worth checking whether wholegrain flour really comes first on the ingredients list; this reading practice is described in the label guide. In people with bowel conditions such as inflammatory bowel disease or irritable bowel syndrome, both the amount and the type of fibre needed can differ, and any adjustment should be made with a doctor and a dietitian.
Increasing fibre comes down to three words: varied, gradual and well watered. Fibre from different sources is more balanced than leaning on one; a slow increase protects digestion; and enough water keeps the whole system running smoothly.
Frequently asked questions
Does fibre help with weight control?
Fibre-rich foods generally keep you full for longer and are low in energy density, and in that way they can support a balanced routine. Fibre alone offers no guarantee of a result, though; the whole pattern is what counts.
Should I take a fibre supplement?
The priority is always to get fibre from food, because fibre-rich foods also carry vitamins and minerals. Whether a supplement is needed, and which type, is a decision to make with a doctor or dietitian.
Is there fibre in fruit juice?
Most of the fibre is lost in strained fruit juice, as the pulp stays in the sieve. Eating the fruit itself means taking the same sugar along with fibre and fullness.
Does the 25 gram figure apply to children too?
No; reference values for children vary with age and are generally lower. Targets for a child's diet are best set with a paediatrician or dietitian.
This guide draws on the general reference values for fibre intake of the European Food Safety Authority (EFSA) and of the Turkey Dietary Guidelines, the national nutrition guidance published for Türkiye.