Fibre: The Nutrient Most People Under-Eat and Underestimate

Why Fibre Deserves More Attention Than It Gets

Protein draws headlines. Omega-3s have devoted followings. But fibre — one of the most consistently well-supported nutrients in nutrition science — rarely generates excitement, even though research links adequate intake to digestive health, more stable blood sugar, cardiovascular health, and a thriving gut microbiome.

The gap between how much fibre people need and how much they actually eat is striking. By most estimates, the average US adult consumes roughly half the generally recommended daily amount. That shortfall has real implications, because fibre isn't a passive bystander in digestion — it's an active participant in how the body processes food, manages energy, and supports the trillions of bacteria that live in the gut.

Understanding fibre doesn't require a science degree. It starts with knowing what it is, where it comes from, and what happens when you eat more of it — or too little.

What Fibre Actually Does in the Body

Because fibre resists digestion in the small intestine, it travels to the large intestine (colon) largely intact. There, it does several important things depending on its type.

Soluble fibre dissolves in water and forms a thick gel. This gel slows the movement of food through the digestive tract, which can moderate blood sugar spikes after meals and help lower LDL cholesterol levels over time. Oats, barley, apples, and legumes are rich in soluble fibre.

Insoluble fibre doesn't dissolve — it adds bulk to stool and helps material move through the intestines more efficiently, supporting regular bowel movements. Whole wheat, vegetables, and the skins of fruits and legumes are good sources.

Both types also feed the gut microbiome — the community of bacteria and other microorganisms living in your digestive system. When gut bacteria ferment fibre, they produce compounds called short-chain fatty acids, which support the health of the colon lining and may play roles in immune function and inflammation. For a deeper look at how the two fibre types differ, see our guide to soluble and insoluble fibre.

“Dietary fibre is unique among nutrients in that it is not broken down for energy, yet it has profound effects on the health of the gastrointestinal tract and beyond. It truly acts as a prebiotic — feeding the microorganisms that, in turn, benefit us.”

— Joanne Slavin, Professor of Food Science and Nutrition, University of Minnesota, and longstanding contributor to fibre research

Where to Find Fibre in Everyday Foods

Fibre exists naturally only in plant foods. There's none in meat, fish, dairy, or eggs. The best sources are minimally processed whole foods:

• Legumes: Lentils, black beans, chickpeas, and split peas pack 7–16 grams of fibre per cooked cup, making them among the most concentrated sources available.
• Whole grains: Oats, barley, quinoa, and bulgur retain their fibre-rich bran layer, unlike refined grains that have had it stripped away.
• Vegetables: Broccoli, Brussels sprouts, carrots, artichokes, and leafy greens all contribute, especially when eaten with their edible skins.
• Fruits: Raspberries, pears, apples, and avocados are standout sources. Juice removes most of the fibre — eating the whole fruit is better.
• Nuts and seeds: Chia seeds, flaxseeds, and almonds add fibre alongside healthy fats.

If you're building the habit of reading food packaging, fibre is listed on the Nutrition Facts label. Our guide to reading a nutrition label explains exactly how to interpret that information.

How to Increase Fibre Without Digestive Discomfort

A common mistake is dramatically increasing fibre intake all at once. When the gut microbiome isn't accustomed to large amounts of fibre, the sudden shift can cause bloating, gas, and cramping — discouraging people from continuing.

The better approach is gradual. Add one higher-fibre food at a time over several weeks, allowing the digestive system and gut bacteria to adjust. Drinking enough water is equally important — fibre, especially soluble fibre, needs water to do its job properly. Without adequate hydration, increasing fibre can sometimes worsen constipation rather than relieve it.

Simple swaps make a meaningful difference: choosing whole-grain bread over white, adding beans to soups or salads, snacking on fruit rather than crackers, or stirring oats into a smoothie. These small changes compound over the course of a day. Fibre is a carbohydrate — and understanding how it fits alongside other carbs is part of a broader picture of nutrition. Our macronutrients explainer covers that context clearly.

This article is for general informational and educational purposes only and is not a substitute for personalised medical or dietary advice. Consult a qualified healthcare professional or registered dietitian for guidance specific to your health needs.