Dietary fibre is the part of plant foods that resists digestion in the small intestine. Unlike carbohydrates such as sugars and starches, fibre is not broken down and absorbed as glucose. Instead, it passes into the large intestine, where it plays structural, mechanical and metabolic roles that are fundamental to human health.
For decades, fibre was thought of simply as “roughage” - useful mainly for preventing constipation. We now know that fibre does far more than keep things moving.
Large-scale meta-analyses involving hundreds of thousands of participants show that higher dietary fibre intake is associated with lower risk of:
But these benefits do not come from one single type of fibre. They come from different fibres doing different jobs - some supporting bowel motility, others regulating blood sugar and cholesterol, and others feeding the trillions of microbes living in your gut.
To understand why fibre is so powerful for gut and overall health, we need to break it down into four key categories:
Each overlaps in some ways - but each has a distinct role.
What it is: Soluble fibre dissolves in water and often forms a gel-like substance in the gut.
What it does:
Common sources: Oats, barley, psyllium, chia, flax, legumes, apples.
What it is: Insoluble fibre does not dissolve in water.
What it does:
Common sources: Whole grains, wheat bran, nuts, seeds, vegetable skins, leafy greens.
Beyond soluble and insoluble classifications, fibre can also be described based on how it behaves in the digestive system.
Prebiotic fibres resist digestion in the small intestine and are selectively fermented by beneficial gut bacteria.
What they do:
Examples: Inulin, fructo-oligosaccharides, galacto-oligosaccharides, some resistant starches.
Resistant starch is technically a starch, but it behaves like fibre because it resists digestion and reaches the colon intact.
Types include:
What it does:
| Type | Dissolves in water? | Fermented? | Feeds beneficial bacteria? | Main benefit |
|---|---|---|---|---|
| Insoluble fibre | No | Minimal | No | Stool bulk and movement. |
| Soluble fibre | Yes | Sometimes | Sometimes | Cholesterol and blood sugar support. |
| Prebiotic fibre | Usually | Yes | Yes, selectively. | Microbiome support and SCFA production. |
| Resistant starch | No | Yes | Often. | Butyrate production and gut barrier support. |
Large analyses consistently associate higher fibre intake with reduced cardiovascular disease risk, reduced colorectal cancer risk, and lower all-cause mortality.
Too much of one type - particularly rapidly fermented prebiotic fibre - can cause bloating or constipation if introduced too quickly or without adequate hydration.
If you have experienced this, read Can too much fibre cause constipation?
If you are unsure whether your gut is functioning optimally, see 5 signs of an unhealthy gut.
The easiest way to increase fibre intake is to focus on whole plant foods.
Practical ways to add more fibre:
Swap white bread, pasta and rice for wholegrain versions.
Add beans, lentils or chickpeas to soups, stews and salads.
Include nuts and seeds (chia, flax, almonds) daily.
Eat fruit and vegetables with the skin on where possible.
Add oats, ground flaxseed or chia seeds to yoghurt or porridge.
Include resistant starch sources such as cooked and cooled potatoes or rice.
If you struggle to hit your daily target through food alone, a high-quality fibre supplement can help bridge the gap.
In the UK, adults are officially recommended to consume at least 30 grams of fibre per day.
However, most adults consume closer to 18–20 grams daily.
Emerging research consistently shows that higher fibre intakes are associated with greater reductions in cardiovascular disease, type 2 diabetes and colorectal cancer risk. In other words, 30 grams should be seen as a minimum target, not a ceiling.
As long as fibre is increased gradually and paired with adequate hydration, higher intakes from diverse plant sources are generally beneficial.
Yes. A medium banana contains approximately 2–3 grams of fibre.
Bananas provide mostly soluble fibre. Slightly green (less ripe) bananas also contain resistant starch, which behaves like prebiotic fibre and feeds beneficial gut bacteria.
Yes, spinach contains fibre. One cup of cooked spinach provides around 4g of fibre, while a cup of raw spinach contains about 0.7g, making it a useful plant-based source of dietary fibre that supports digestion and gut health.
Yes, Weetabix contains fibre. Two Weetabix biscuits provide roughly 3–4g of fibre, mainly from whole wheat, which can help support digestive health and contribute towards the recommended daily fibre intake.
Yes, mango contains fibre. One cup of fresh mango provides about 2–3g of dietary fibre, which can support digestion and contribute to your daily fibre intake when eaten as part of a balanced diet.
Yes, lettuce contains fibre. One cup of shredded lettuce provides around 0.5–1g of fibre, depending on the variety, making it a small but helpful contributor to daily fibre intake when included regularly in meals.
Yes, sweet potatoes are a good source of fibre. One medium sweet potato with the skin provides roughly 3–4g of fibre, which can support digestive health and help you move closer to the recommended daily fibre intake.
The best fibre supplement is one that provides a meaningful dose of diverse fibres, not just a single isolated ingredient.
When choosing a fibre supplement, look for:
A blend of soluble and prebiotic fibres
A substantial fibre dose per serving
Minimal added sugars
Additional gut-supporting ingredients where appropriate
For example, Biomel Complete Gut contains added fibre alongside live cultures, and our prebiotic bars provide a substantial 13 grams of fibre per bar helping make a real contribution toward your daily 30g+ target.
Rather than thinking of fibre supplements as a quick fix, the goal should be to use them to support a fibre-rich dietary pattern overall.
Yes, grapes contain fibre. One cup of grapes provides around 1–1.5g of dietary fibre, making them a small but helpful contributor to daily fibre intake when eaten as part of a balanced diet.
Yes, carrots are a good source of fibre. One medium carrot contains about 1.5–2g of fibre, which can support digestive health and help contribute towards your daily recommended fibre intake.
Avocados are high in fibre. One whole avocado contains roughly 10g of fibre, making it one of the most fibre-rich fruits and a helpful food for supporting gut health and digestion.
Fibre is not just about bowel movements. It plays a role in feeding beneficial microbes, producing anti-inflammatory metabolites, protecting the gut lining, supporting metabolic and heart health, and reducing long-term disease risk.
The goal is not simply more fibre. It is the right mix of fibre types. Your gut ecosystem thrives on diversity and fibre diversity is what feeds it.
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