Fiber

What Is Dietary Fiber?

Dietary fiber refers to the non-digestible carbohydrate components of plant foods that pass largely intact through the small intestine and reach the large intestine. Fiber is broadly categorized as soluble (dissolves in water to form a gel-like substance) or insoluble (does not dissolve and adds bulk to stool). Most plant foods contain a mixture of both types.

Unlike other carbohydrates, fiber provides minimal calories — soluble fiber yields approximately 2 kcal per gram through fermentation by gut bacteria, while insoluble fiber provides virtually none.

Health Benefits

A high-fiber diet is associated with numerous health benefits supported by substantial epidemiological and clinical evidence:

• Cardiovascular health: soluble fiber (e.g., beta-glucan in oats) reduces LDL cholesterol by binding bile acids
• Blood sugar regulation: slows glucose absorption, reducing postprandial blood sugar spikes
• Digestive health: insoluble fiber promotes regular bowel movements and reduces constipation
• Gut microbiome: fermentable fibers act as prebiotics, feeding beneficial bacteria
• Weight management: increases satiety and reduces overall energy intake

Recommended Intake and Food Sources

The Adequate Intake (AI) for fiber is 25 g/day for adult women and 38 g/day for adult men. Most people in Western countries consume only 15–17 g/day — well below recommendations.

• Split peas (1 cup cooked): 16 g fiber
• Lentils (1 cup cooked): 15 g fiber
• Avocado (1 medium): 10 g fiber
• Oat bran (1/2 cup dry): 7 g fiber
• Chia seeds (28 g): 10 g fiber