Fibre and gut health: how much, where from, and the easy swaps

Nobody gets excited about fibre. It has no marketing budget, and the main thing people know is that it keeps you regular. True, and worth having. But the guidance on both sides of the Atlantic gives it a much bigger job — and reports that almost everyone is falling short.

This is general information, not dietary advice. If you have a bowel condition, diverticular disease, or have been told to limit fibre for any reason, check with your GP (family doctor) or a registered dietitian before changing anything.

What fibre does for you

The NHS (the UK health service) lists the conditions that a higher-fibre diet is associated with a lower risk of: “heart disease, stroke, type 2 diabetes and bowel cancer.” It also helps digestion and prevents constipation, which is why most people first pay attention.

The British Dietetic Association adds the gut-bacteria angle: fibre helps improve the diversity of the bacteria in your gut, with knock-on benefits for immunity and inflammation. The 2025–2030 US Dietary Guidelines say the same in three words — “high-fiber foods support a diverse microbiome” — and tell readers to “prioritize fiber-rich whole grains.”

How much?

• UK: the government target, quoted by both the NHS and the BDA, is 30g a day for adults. The NHS says most adults “are only eating an average of about 20g” a day; the BDA puts the average at 18g, “60% of what it should be.”
• US: the guidance for older adults gives 22g a day for women over 51 and 28g for men over 51. The same document notes that “there is an underconsumption of calcium, potassium, dietary fiber, and vitamin D in the general population” and that these low intakes “are a public health concern.”

Wherever you live, the gap is about a third. That sounds like a lot until you see how much fibre sits in ordinary foods.

Where fibre comes from

Fibre only comes from plants: wholegrains, vegetables, fruit, beans, lentils, nuts and seeds. Meat, fish, eggs and dairy have none. That does not mean going vegetarian; it means the plant half of the plate has to do its job.

The BDA’s per-100g figures give a sense of scale: bran-based cereals carry 13–24.5g, sesame seeds 7.9g, almonds 7.4g, figs 6.9g and boiled peas 5.6g. The NHS works at meal level, which is more useful in a kitchen: wholemeal spaghetti with a lentil and tomato sauce comes to around 11g of fibre in one lunch, and a dinner of grilled chicken, a skin-on baked potato, carrots and green beans to about 11.2g. Two meals like that and you are two-thirds of the way to 30g before you have eaten breakfast.

The US guidance for older adults gives the same list in a sentence: “increasing vegetables, fruits, beans, whole grains, and dairy within meals will help participants reach the recommended intakes.” (Dairy is there for the calcium; fibre is the rest of the list.) MyPlate suggests adults over 60 aim for 3 to 3½ “ounce-equivalents” of wholegrains a day, and notes that “consuming whole grain foods that contain fiber, as part of an overall healthy diet, can support healthy digestion.”

Easy swaps, meal by meal

You do not need new recipes. You need the same meals with one ingredient changed.

• Breakfast. The NHS suggests “a higher-fibre breakfast cereal such as plain wholewheat biscuits” or porridge. Add fruit on top — a banana or a handful of berries — and the bowl does more work.
• Bread. Wholemeal or seeded instead of white. Same sandwich, more fibre. If you cannot stand wholemeal, the “50/50” loaves are a fair compromise.
• Potatoes. Leave the skin on. The NHS dinner example specifies a “skin-on baked potato” for a reason.
• Pasta and rice. Wholemeal pasta and brown rice. If the switch is too abrupt, do half and half for a month.
• Beans in everything. A tin of lentils into a bolognese, chickpeas into a curry, kidney beans into a chilli. The NHS lunch example — lentils with wholemeal spaghetti — is exactly this.
• Snacks. The NHS list is “fresh fruit, vegetable sticks, rye crackers, oatcakes, and unsalted nuts or seeds.” An apple and a handful of almonds beats a biscuit on every count.
• Five a day, with the skin. Fruit and vegetables with skins and seeds — pears, apples, berries, peas, sweetcorn — carry more fibre than peeled or juiced versions.

The two rules that prevent regret

Go gradually. The BDA is explicit: “If you increase your fibre intake, do it gradually to avoid gastrointestinal symptoms such as bloating and gas.” One swap a week is plenty. Your gut bacteria need time to adjust to the new menu.

Drink more. Again from the BDA: “Remember to drink plenty of fluid to allow the fibre to do its job properly. Fibre draws water into the bowel.” Fibre without water is how people end up more constipated than when they started. See Hydration and alcohol after 50 for how much is enough.

Bringing it together

A higher-fibre breakfast, wholemeal bread, skins left on, a tin of pulses in the week’s main dish, and a glass of water with each meal. Added one at a time over a month, that is the difference between 18g and 30g, and it costs nothing.

If you would rather have the swaps scheduled — which week to change the bread, which week to add the beans — our Eat Strong four-week kitchen planner gives fibre a week of its own. For the wider picture, start with Eating well after 50: the complete, no-fad guide.

This week

• Change breakfast to porridge or wholewheat biscuits with fruit.
• Add one tin of beans, lentils or chickpeas to a meal you already make.
• A glass of water with every meal, no exceptions, for seven days.