What is fibre and why does it matter?
Fibre is the part of plant foods that your body cannot fully digest. In the US it is spelled fiber, and you may see it called dietary fibre or roughage.
It passes through your gut and does useful work along the way. It keeps you regular, feeds helpful gut bacteria and helps you feel full.
Diets high in fibre are linked with a lower risk of heart disease, type 2 diabetes and constipation, according to the Harvard Nutrition Source.
Soluble fibre
Soluble fibre dissolves in water and turns into a gel. This gel can help lower blood cholesterol and slow the rise in blood sugar after a meal.
Oats, barley, beans, apples and chia seeds are good sources.
Insoluble fibre
Insoluble fibre does not dissolve. It adds bulk and helps food move through your gut at a steady pace.
Whole grains, nuts, and the skins of fruit and vegetables are rich in it. Most foods contain both types, so you do not need to track them separately.
How much fibre do you need each day?
Most adults are advised to eat about 21 to 38 grams of fibre a day. The exact figure differs between health bodies, so here is what each says.
| Source | Grams per day |
|---|---|
| MedlinePlus (US) | 21 to 38 g |
| Harvard Nutrition Source | At least 25 to 35 g |
| NHS (UK) | 30 g |
The Harvard Nutrition Source suggests at least 25 to 35 grams, and the NHS suggests 30 grams for adults.
Most people fall short. Harvard puts the average US intake at about 15 grams, and the NHS says adults in the UK average about 20 grams.
These are general targets for healthy adults. Needs change with age, health conditions and medicines, so a registered dietitian can set a target that fits you.
The 12 best fibre-rich foods
These foods are easy to find, affordable and simple to cook. Fibre amounts are approximate and vary by brand and how you prepare them.
You can check exact values for any food in the USDA FoodData Central database.
| Food | Serving | Fibre |
|---|---|---|
| Lentils, cooked | 1 cup | About 15 g |
| Black beans, cooked | 1 cup | About 15 g |
| Raspberries | 1 cup | About 8 g |
| Chia seeds | 1 ounce (28 g) | About 10 g |
| Barley, cooked | 1 cup | About 6 g |
| Broccoli, cooked | 1 cup | About 5 g |
| Avocado | Half a medium fruit | About 5 g |
| Apple with skin | 1 medium | About 4.5 g |
| Rolled oats, dry | Half a cup | About 4 g |
| Sweet potato, baked with skin | 1 medium | About 4 g |
| Almonds | 1 ounce (about 23 nuts) | About 3.5 g |
| Whole grain bread | 1 slice | 2 to 4 g |
1. Lentils
About 15 g per cooked cup
Lentils are one of the most fibre-dense foods you can buy. They also bring plant protein and cook in about 20 minutes with no soaking.
Stir them into soups, curries and salads, or mash them into a simple dal.
2. Black beans
About 15 g per cooked cup
Black beans match lentils for fibre. They hold their shape well, so they suit tacos, rice bowls and chilli.
Canned beans work fine. Rinse them well to cut down on salt.
3. Raspberries
About 8 g per cup
Raspberries are the fibre champion of the fruit aisle. Their tiny seeds and soft flesh both add fibre.
Frozen raspberries work as well as fresh and keep for months.
4. Chia seeds
About 10 g per ounce
Chia seeds soak up liquid and form a gel, which is why chia pudding is so thick. A spoonful goes a long way.
Always mix them into liquid or yoghurt first rather than swallowing them dry.
5. Oats
About 4 g per half cup, dry
Oats contain beta-glucan, a soluble fibre linked to lower LDL cholesterol. Porridge is the easiest way to eat them.
Top a bowl with raspberries and chia and you have three foods from this list before 9 a.m.
6. Barley
About 6 g per cooked cup
Barley is a chewy whole grain that also contains beta-glucan. Use it in place of white rice in soups, stews and pilafs.
Barley contains gluten, so it is not suitable if you have coeliac disease.
Want the whole plan in one place?
Our Healthy Eating Guide shows how fibre fits with protein, healthy fats and portions, chapter by chapter.
7. Avocado
About 5 g per half fruit
Avocado is unusual because it pairs fibre with healthy fats. That combination keeps you full for longer.
Spread it on whole grain toast or add slices to a salad.
8. Broccoli
About 5 g per cooked cup
Broccoli is a top vegetable for fibre. Steam it lightly so it stays firm and bright green.
Eat the stalks too. They are full of fibre and taste mild when sliced thin.
9. Apples
About 4.5 g per medium apple
Much of an apple's fibre sits in the skin, so wash it well and eat it whole. Apple juice has almost none.
An apple is an easy snack that needs no prep.
10. Almonds
About 3.5 g per ounce
A small handful of almonds adds fibre, protein and healthy fat. They are also easy to carry.
Keep portions modest, because nuts are high in calories.
11. Sweet potatoes
About 4 g per medium potato
Bake sweet potatoes with the skin on to get the most fibre. They also supply vitamin A and potassium.
Roast wedges, mash them, or cube them into a grain bowl.
12. Whole grain bread
2 to 4 g per slice
Look for bread where the first ingredient is whole wheat or another whole grain. Words like "multigrain" or "wheat bread" do not guarantee that.
Compare the fibre line on the label and pick the loaf with the higher number per slice.
Check how much protein you needHow to eat more fibre without stomach trouble
A sudden jump in fibre can cause gas, bloating and cramps. The fix is to go slowly.
Add fibre in small steps
- Pick one meal, such as breakfast, and add one fibre-rich food.
- Keep that change for a week.
- Add a second food at another meal the next week.
- Keep going until you reach your target over two to three weeks.
Drink enough fluid
Fibre works best with water. The Harvard Nutrition Source notes that drinking enough fluid helps limit side effects as you eat more fibre.
Not sure how much is enough? Our guide on how much water you need each day gives a realistic range.
Easy swaps that add fibre
- Choose whole fruit instead of juice.
- Swap white rice for barley, brown rice or bulgur.
- Swap white bread for whole grain bread.
- Replace some meat with beans or lentils two or three times a week.
- Leave the skin on potatoes, apples and sweet potatoes.
- Snack on almonds or raw vegetables.
Fibre also helps you feel full, which can support steady eating habits. See how it fits into a bigger plan on our Weight Management hub.
Plan a week of fibre-rich meals in one hourWhat a 30-gram fibre day can look like
Here is one example. Portions are rough, so the total lands between about 30 and 35 grams.
- Breakfast: Half a cup of dry oats cooked as porridge, topped with half a cup of raspberries. About 8 g.
- Lunch: Three-quarters of a cup of lentil soup with a slice of whole grain bread. About 14 g.
- Snack: One apple, or a small handful of almonds. About 4 g.
- Dinner: A cup of steamed broccoli beside grilled fish and half a baked sweet potato. About 7 g.
Your own plate will look different, and that is fine. Build a balanced plate that includes at least one high-fibre food at each meal.
Common fibre mistakes to avoid
- Going too fast. Doubling your fibre in a day is the quickest route to bloating.
- Skipping water. Extra fibre with too little fluid can make you feel more blocked, not less.
- Trusting the front of the pack. Terms like "high fibre" or "made with whole grain" need a check against the nutrition label.
- Peeling everything. The skins of apples, potatoes and sweet potatoes hold much of the fibre.
- Relying on supplements. Powders lack the vitamins and plant compounds you get from whole foods.
- Eating dry chia seeds. Soak them first, because they swell when wet.
Who should be careful with high-fibre foods?
For most healthy people, fibre-rich foods are safe and helpful. A few groups should check with a doctor first.
- People with inflammatory bowel disease, especially during a flare.
- People with a narrowed bowel, a recent bowel operation or swallowing problems.
- People with irritable bowel syndrome, who may tolerate some fibres better than others.
- People with coeliac disease, who need gluten-free grains instead of barley and standard whole grain bread.
- Anyone on a medically prescribed diet.
Severe belly pain, ongoing constipation or diarrhoea, blood in your stool or unexplained weight loss need medical attention. Do not treat these with diet changes alone.
Recap: your fibre plan in five points
- Aim for about 21 to 38 grams a day (US guidance), or 30 grams by NHS advice.
- Start with beans, lentils, berries, oats and whole grains.
- Add one food at a time and build up over two to three weeks.
- Drink water through the day.
- Choose whole foods first and speak to a professional if you have a gut condition.
Fibre-rich foods: frequently asked questions
Lentils, black beans, raspberries, chia seeds, oats, barley, avocado, broccoli, apples, almonds, sweet potatoes and whole grain bread are all strong sources. Beans and lentils lead the list, with about 15 grams of fibre in a cooked cup.
Most healthy adults are advised to eat about 21 to 38 grams of fibre a day, according to US guidance. The Harvard Nutrition Source suggests 25 to 35 grams, and the NHS suggests 30 grams for adults. Most people eat well below these amounts.
Soluble fibre dissolves in water and forms a gel that can help lower blood cholesterol and slow the rise in blood sugar. Insoluble fibre does not dissolve and adds bulk that helps food move through the gut. Most plant foods contain both types.
Yes. A sudden jump in fibre can cause gas, bloating, cramps and loose or hard stools. Add fibre slowly over a few weeks and drink enough fluid. If symptoms last, speak to a doctor or registered dietitian.
Whole foods are usually the better choice because they also give you vitamins, minerals and other plant compounds. Supplements can help some people who cannot reach their target with food, but check with a doctor or registered dietitian first.
Add one new fibre-rich food at a time, increase portions slowly over two to three weeks, drink water through the day and rinse canned beans well. Cooking beans and lentils until soft also makes them easier to digest.
Sources and further reading
We checked fibre targets and health claims against these sources. Food values are approximate and taken from typical USDA entries.
- Harvard T.H. Chan School of Public Health, The Nutrition Source: Fiber
- NHS: How to get more fibre into your diet
- MedlinePlus (US National Library of Medicine): Dietary fiber
- World Health Organization: Healthy diet fact sheet
- USDA FoodData Central
Not sure where to start? Head back to the Nutrition hub for more articles, or read the Healthy Eating Guide.
