Fibre: The Nutrient Most People Underestimate

Why Fibre Deserves More Attention

When people think about nutrients to watch, protein, vitamins, and calcium often come to mind first. Fibre rarely gets top billing—yet research consistently links adequate fibre intake to meaningful health benefits, and most people in the United States consume far less than recommended amounts.

Fibre is unique among carbohydrates because the body lacks the enzymes needed to break it down fully. Rather than being absorbed as fuel, it moves through the digestive tract, doing quiet but consequential work along the way. Understanding what fibre actually does—and where to find it—is one of the more practical steps you can take toward a nutritionally sound diet.

Two Types of Fibre, Two Sets of Benefits

Dietary fibre is not a single substance. It divides into two main categories, each with distinct effects in the body:

• Soluble fibre dissolves in water and forms a viscous gel in the digestive tract. This gel slows the absorption of glucose, which can help keep blood sugar levels more stable after meals. It also binds to cholesterol-containing compounds in the gut, which may support healthy blood cholesterol levels over time. Oats, barley, legumes, apples, and citrus fruits are good sources.
• Insoluble fibre does not dissolve in water. It adds bulk to stool and helps food move through the intestines more efficiently, supporting regular bowel movements. Whole wheat products, bran, most vegetables, and nuts are rich in this type.

Most plant foods contain both types in varying proportions, so eating a diverse range of whole plant foods naturally provides a mix of both. When reading a nutrition label, the fibre figure shown reflects total dietary fibre from all sources in that food.

Fibre and the Gut Microbiome

One of fibre's most significant roles is as a food source for the trillions of bacteria that live in the large intestine—collectively known as the gut microbiome. When beneficial bacteria ferment soluble fibre, they produce short-chain fatty acids (SCFAs), compounds that help maintain the lining of the intestine, support immune function, and may play a role in reducing inflammation.

A diverse, fibre-rich diet is associated with a more diverse gut microbiome, which researchers generally view as a marker of better gut health. By contrast, diets low in fibre tend to be associated with reduced microbial diversity. This is an active area of scientific research, and much is still being studied, but the connection between fibre intake and gut microbiome health is well-supported by current evidence.

“The gut microbiome is exquisitely sensitive to what we eat. Dietary fibre is the primary fuel for the beneficial microbes that maintain intestinal health, and a shortfall has consequences that extend well beyond digestion.”

— Justin Sonnenburg, Professor of Microbiology and Immunology, Stanford University

Practical Ways to Eat More Fibre

Increasing fibre intake doesn't require an overhaul of your eating habits. Small, consistent swaps and additions can make a meaningful difference:

• Choose whole grain versions of bread, pasta, and rice rather than refined grain alternatives.
• Add legumes—lentils, chickpeas, black beans—to soups, salads, or grain bowls a few times a week.
• Eat fruit with the skin on where edible (e.g., apples, pears), since much of the fibre sits in or just beneath the skin.
• Snack on nuts or seeds rather than processed snacks.
• Load at least half your plate with vegetables at main meals.

One important note: when significantly increasing your fibre intake, do so gradually and drink plenty of water. A sudden large increase can cause bloating or gas as your digestive system adjusts. If you have a digestive condition or other health concerns, consult a healthcare professional before making major dietary changes.

For a broader look at how fibre fits into a full day of balanced eating, see what a nutritionally sound day of eating looks like for different lifestyles. And if you're curious about how fibre relates to common nutrition misconceptions, nutrition myths that refuse to die offers a useful evidence-based perspective.

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