What Is Dietary Fibre?
Dietary fibre is a type of carbohydrate found in plant foods that the human body cannot fully digest. Unlike sugars and starches that break down into glucose, fibre passes largely intact through the digestive tract. This distinction makes it unique among carbohydrates — and unusually beneficial. Learn more in our article on how fibre differs from other carbohydrates.
There are two main types: soluble fibre, which dissolves in water to form a gel-like substance, and insoluble fibre, which adds bulk to stool and helps food move through the digestive system. Most plant foods contain a mix of both types, which is why variety in your diet matters.
Soluble fibre
A type of dietary fibre that dissolves in water to form a gel in the digestive tract. It helps slow digestion and is associated with benefits for blood sugar and cholesterol levels. Found in oats, apples, beans, and barley.
Insoluble fibre
A type of dietary fibre that does not dissolve in water. It adds bulk to stool and helps food pass more quickly through the intestines, supporting regular bowel movements. Found in whole wheat, nuts, and many vegetables.
Prebiotic
A type of dietary compound — often a fibre — that serves as food for beneficial bacteria in the gut. Prebiotics help support a healthy gut microbiome, which plays a role in digestion and immune function.
Gut microbiome
The community of trillions of microorganisms, including bacteria, that live in the digestive tract. A diverse, well-nourished microbiome is associated with better digestive health and broader wellbeing.
Fibre is found in vegetables, fruits, legumes, whole grains, nuts, and seeds. It is not found in meat, dairy, or processed foods that have had their plant components removed during manufacturing.
Why Fibre Matters for Your Health
Fibre performs several well-documented functions in the body. Understanding them helps explain why dietary guidelines consistently emphasize it as a priority nutrient.
| Recommended daily intake (women) | 25 grams (Academy of Nutrition and Dietetics) |
| Recommended daily intake (men) | 38 grams (Academy of Nutrition and Dietetics) |
| Average US adult intake | ~15 grams/day (Dietary Guidelines for Americans) |
| Primary food sources | Vegetables, fruits, legumes, whole grains, nuts, seeds |
| Types of dietary fibre | Soluble and insoluble |
- Digestive regularity: Insoluble fibre adds bulk to stool, helping prevent constipation and supporting predictable bowel movements.
- Blood sugar management: Soluble fibre slows the absorption of sugar into the bloodstream, which can help moderate blood glucose responses after meals.
- Cholesterol levels: Certain soluble fibres — particularly beta-glucan found in oats — have been shown to help reduce LDL (low-density lipoprotein) cholesterol when consumed regularly as part of a varied diet.
- Satiety: Fibre-rich foods tend to be more filling, which can support appetite regulation without requiring strict calorie counting.
- Gut microbiome: Many fibres act as prebiotics, feeding beneficial bacteria in the large intestine. A well-nourished microbiome is associated with broader markers of digestive and immune health. See how this fits into a broader eating pattern in our guide on building a gut-friendly eating pattern.
Fibre intake is also one of the nutrients most frequently underconsumed. It commonly appears among the gaps people leave in their nutrient intake even in otherwise balanced diets.
How Much Fibre Do Adults Need?
The DGA and the Academy of Nutrition and Dietetics recommend approximately 25 grams per day for women and 38 grams per day for men (or roughly 14 grams per 1,000 calories consumed). Most US adults consume closer to 15 grams daily — well below either target.
~15g
Average daily fibre intake in US adults
According to the Dietary Guidelines for Americans, most US adults consume roughly 15 grams of fibre daily — well below the recommended amount.
95%
Americans not meeting fibre recommendations
Research published in the American Journal of Lifestyle Medicine estimates that approximately 95% of Americans do not meet daily fibre intake targets.
Rather than dramatically overhauling your diet overnight, gradually increasing fibre intake is generally better tolerated. Sudden large increases can cause bloating or gas as your gut adjusts. Pairing increased fibre with adequate water intake also supports comfortable digestion.
Men often fall short on multiple nutrients alongside fibre. If that applies to you, the article on micronutrients men commonly fall short on offers relevant context on broader nutritional gaps.
This article is for informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional before making significant changes to your diet, particularly if you have a digestive condition or other health concerns.
