What is dietary fibre and why does it matter?
Dietary fibre is the part of plant foods that your body cannot fully digest. Instead of being absorbed, it moves through your gut, where it feeds your friendly gut bacteria, keeps you regular and slows the absorption of sugar and cholesterol. There are two main types:
- Soluble fibre (oats, barley, lentils, beans, apples, citrus, chia) forms a gel that helps lower LDL cholesterol and steadies blood sugar.
- Insoluble fibre (wholegrains, wheat bran, nuts, vegetable skins) adds bulk and helps prevent constipation.
Large studies show people who eat 25–29 g of fibre a day or more have a 15–30% lower risk of heart disease, stroke, type 2 diabetes and bowel cancer than those who eat little fibre. Yet most adults eat only around 15–20 g a day.
How the fibre calculator works
If you enter your daily calories, the calculator uses the Dietary Guidelines rule of 14 g of fibre per 1,000 kcal. For example, 1,800 kcal × 14 ÷ 1,000 = 25 g. If you leave calories empty, it uses the reference intake for your age and sex shown below.
Daily fibre intake chart
| Age | Girls / women | Boys / men |
|---|---|---|
| 2 – 3 years | 14 g | 14 g |
| 4 – 8 years | 17 g | 20 g |
| 9 – 13 years | 22 g | 25 g |
| 14 – 18 years | 25 g | 31 g |
| 19 – 30 years | 28 g | 34 g |
| 31 – 50 years | 25 g | 31 g |
| 51+ years | 22 g | 28 g |
Low, normal and high fibre intake (adults)
| Daily fibre | Level | What it means |
|---|---|---|
| Under 20 g | Low | Common; linked with constipation, blood sugar spikes and higher heart disease risk |
| 25 – 38 g | Normal / target | Meets WHO and dietary guideline targets for most adults |
| Over 50 g | High | Usually fine if increased slowly with enough water; may cause bloating or reduce mineral absorption in some people |
Health benefits of eating enough fibre
- Better digestion and relief from constipation (see our constipation diet guide).
- A healthier gut microbiome — fibre is food for beneficial bacteria.
- Steadier blood sugar, useful for diabetes, prediabetes, PCOS and insulin resistance.
- Lower LDL cholesterol and blood pressure.
- Easier weight control: fibre-rich foods fill you up for fewer calories.
- Lower risk of bowel cancer.
Health warnings
- Increase fibre gradually (about 5 g a week) and drink more water, or you may get gas, bloating and cramps.
- People with IBS may need to limit certain fibres (high-FODMAP foods) — see our bloating guide.
- During a flare of Crohn’s disease or ulcerative colitis, or with a bowel narrowing, a low-fibre diet may be advised by your doctor.
- Fibre supplements can affect how some medicines are absorbed — take them at least 2 hours apart.
Easy ways to eat more fibre
Choose whole-wheat roti, brown or mixed rice and oats instead of white flour and white rice; add a cup of dal, chickpeas or beans to your day; eat fruit with the skin; snack on nuts, roasted chana or vegetables with hummus; and add chia or flaxseed to yoghurt. Our guide unlocking the power of dietary fibre and the free gut-friendly meal plan make it easy.
Frequently asked questions
How much fibre should I eat per day?
Most adult women need about 25–28 g and men about 31–34 g of fibre a day, or about 14 g for every 1,000 kcal you eat. The WHO recommends at least 25 g a day for adults.
What foods are highest in fibre?
Lentils, beans, chickpeas, chia and flaxseeds, oats, barley, wholegrain bread and roti, vegetables such as broccoli and okra, berries, pears, apples with skin and nuts are all good sources.
Can too much fibre be bad for you?
Eating a lot of fibre suddenly can cause bloating, gas and cramps. Increase slowly and drink plenty of water. Very high intakes (over 50–70 g) are rarely needed.
Does fibre help with weight loss?
Yes. High-fibre foods are filling and lower in calories, and they slow digestion so you stay full for longer. Studies link higher fibre intake with lower body weight.
Should I take a fibre supplement?
Food is the best source because it also provides vitamins, minerals and plant compounds. A supplement such as psyllium can help if you cannot reach your target from food — ask your doctor first if you take medicines.
Sources
- Reynolds A, et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet 2019;393:434–445.
- U.S. Dietary Guidelines for Americans 2020–2025, Appendix 1 (fibre).
- WHO. Carbohydrate intake for adults and children: WHO guideline. 2023.