Understanding Fibre and Where to Find It

Fibre is one of the few parts of food where most official advice says “more” rather than “less”. It is also one where the figures are often quoted without saying where they come from. This article answers the questions people most often ask about it, and names the source of every number.

What is fibre?

The British Dietetic Association (BDA) describes dietary fibre as the part of plant foods that is not digested in the small intestine. It passes on to the large intestine, where bacteria break it down fully or partly. Because it comes from plants, you find it in grains, vegetables, fruit, pulses, nuts and seeds.

The BDA lists several kinds, including soluble fibre (in fruit and oats, for example), insoluble fibre (in wheat bran and nuts) and resistant starch (in bananas, potatoes, grains and pulses). You do not need to track the types. The NHS simply suggests getting fibre from a variety of sources.

How much is recommended, and by whom?

The answer depends on which body you ask, and what the figure is for.

These are population-level reference points, not personal prescriptions. The NHS adds that in the UK, adults on average eat about 20 g a day, so the practical message there is “a bit more than now”. For children, the NHS gives lower figures: about 15 g a day at ages 2 to 5, 20 g at 5 to 11, and 25 g at 11 to 16.

Why does it matter?

The NHS says fibre helps digestion and helps prevent constipation. It also says that eating plenty of fibre is associated with a lower risk of heart disease, stroke, type 2 diabetes and bowel cancer. “Associated with” is the right phrase: this describes what is seen across large groups of people who eat more fibre-rich foods. It is not a promise about any one person, and it is not a reason to treat fibre as a medicine. Our article on association and causation explains the distinction.

Where is it found?

The BDA publishes fibre figures for common foods. A selection, per 100 g unless stated:

Two things stand out. Ordinary, inexpensive foods – bread, peas, tinned beans – do much of the work. And no single food gets you far on its own; it is the spread across the day that adds up.

What does a day with about 30 g look like?

The NHS gives a worked example, with its own estimates:

How can I eat more without changing everything?

The NHS and BDA suggestions are mostly swaps and additions:

• Choose a higher-fibre breakfast cereal such as plain wholewheat biscuits or porridge oats.
• Pick wholemeal or granary bread, wholewheat pasta, bulgur wheat or brown rice some or all of the time.
• Leave the skins on potatoes, and on fruit and vegetables where that is practical.
• Add beans, lentils or chickpeas to stews, curries and salads.
• Keep frozen vegetables to hand so there is always something to add to a meal.
• For snacks, try fruit, vegetable sticks, oatcakes, or unsalted nuts and seeds.

None of these need special products. Tinned and frozen foods count; see fresh, frozen and canned for how they compare.

Should I increase it gradually?

Yes, according to the BDA. It advises increasing fibre gradually to limit bloating and wind, and drinking plenty of fluid, because fibre draws water into the bowel. In practice that might mean making one change, keeping it for a week or two, and then adding another, rather than switching every food on the same day. How much fluid is “plenty” varies from person to person; our hydration article explains why.

What do “high fibre” and “source of fibre” mean on a pack?

The BDA’s guide to reading a UK nutrition label is that 6 g of fibre per 100 g counts as “high fibre” and 3 g or more per 100 g as a “source of fibre”; the NHS gives the same 6 g figure for high-fibre foods. The NHS notes that UK nutrition panels may include fibre but do not always, so its absence from a label does not mean the food has none. Rules for claims and labels differ between countries, which is covered in reading food labels.

Is more fibre right for everyone?

Not automatically. The BDA notes that for people with irritable bowel syndrome, large amounts of fermentable fibre may cause bloating, wind and diarrhoea, and that some conditions, such as inflammatory bowel disease, can restrict how much fibre a person can have. It suggests seeing a dietitian if you have constipation or diarrhoea, have such a condition, or are unsure about the amount or type of fibre you eat.