Fibre: why it matters and how much you need

Fibre is the part of plant food your body cannot digest, and UK public health guidance puts the target for adults at around 30g a day. Most people in the UK fall well short of that. Fibre matters because it keeps you feeling full for longer, feeds the bacteria in your gut, and helps keep your digestion regular. It costs you nothing to eat more of it, and the foods it comes in are cheap and easy to find.

Here is what fibre does and how to actually hit 30g without thinking too hard about it.

What fibre actually is

Fibre is a type of carbohydrate found in plants that your small intestine cannot break down. Because it passes through mostly intact, it does not give you the usable energy that other carbs do. That is a feature, not a flaw. It is exactly why fibre fills you up without piling on calories.

There are two broad kinds, and you want both:

• Soluble fibre dissolves in water and turns into a soft gel as it moves through you. It slows digestion, which helps you feel full and steadies the rise in blood sugar after a meal. Found in oats, beans, lentils, apples and pears.
• Insoluble fibre does not dissolve. It adds bulk and helps things move through your gut smoothly. Found in wholegrain bread, brown rice, nuts, and the skins of fruit and veg.

Most plant foods carry a mix of the two, so you do not need to count them separately. Just eat a range of plants and you cover both.

Why fibre is worth the effort

It keeps you full. Fibre slows down how fast your stomach empties, so a high-fibre meal holds off hunger longer than a low-fibre one with the same calories. If you are eating less to lose weight, fibre is one of the easiest ways to feel less hungry while you do it.

It feeds your gut bacteria. The bacteria living in your large intestine ferment fibre for fuel. A well-fed gut community is linked to better digestion and general health. Fibre is the main thing those bacteria run on, so more fibre means more to work with.

It keeps digestion regular. Insoluble fibre adds bulk and holds water, which makes everything easier to pass. This is the oldest and best-known reason to eat more fibre, and it still holds.

How much you need

UK guidance sets the target for adults at around 30g of fibre a day. That is an average across the day, not a number you need to hit at every meal.

Children need less, scaled to age, so the 30g figure is an adult target. Most UK adults currently eat closer to 20g, so there is a real gap for most people to close.

You do not need to jump straight to 30g overnight. If your gut is not used to it, a sudden jump can leave you bloated or gassy. Build up over a couple of weeks and drink plenty of water alongside, since fibre works better when there is water for it to soak up.

Easy UK sources to hit 30g

You do not need special foods or supplements. Here are everyday items you can buy in any UK supermarket, with rough fibre amounts to give you a feel for the sizes.

String a few of those together across a day and 30g arrives without much planning. Porridge for breakfast, a wholemeal sandwich at lunch, beans or veg with dinner, and a piece of fruit as a snack will get most people there.

A few simple swaps do a lot of the work: white bread to wholemeal, white rice to brown, peeled veg to skin-on, and a piece of fruit instead of a biscuit. Keep the skins on your potatoes and apples, since a fair chunk of the fibre lives right there.

Let the app keep score

Fibre is one of the numbers Fettle (stayfettle.com) tracks as you log your meals, so you can see how close you are to 30g by the end of the day rather than guessing. It has UK foods and barcode scanning, it is free, and there is no account to set up.

One honest note

These figures are general guidance for healthy adults, not medical advice. If you have a gut condition such as IBS or Crohn's, are recovering from bowel surgery, or have been told to follow a low-fibre or specific diet for medical reasons, check with your GP or a registered dietitian before you increase your fibre.