GLOSSARY

Dietary Fiber Types Table

Solubility, viscosity and fermentability are independent fiber properties; classifying one does not fully predict the others.

Dietary Fiber (Fiber) comprises food components resisting small-intestinal digestion that can contribute to bowel function and other nutritional outcomes. Fibre is not one substance with one effect; source, structure and quantity matter.

Definition: Dietary fibre comprises components resistant to small-intestinal digestion and absorption, with definitions and analytical methods differing between authorities. Some definitions admit isolated or manufactured carbohydrates when beneficial physiological effects are demonstrated. Being non-digestible alone does not automatically qualify an ingredient as declared fibre in every labelling framework.

Properties: Solubility, viscosity and fermentability are separate properties. Inulin can be soluble, low-viscosity and readily fermented; psyllium forms gels but is generally less fermented. Two ingredients described as soluble fibre therefore need not produce the same intestinal consistency, gas production or post-meal response.

Large-intestinal microbes can convert some remaining carbohydrates into short-chain fatty acids and gases. This differs from direct glucose absorption and cannot be treated as equivalent rapid running fuel. Both the amount and rate of fermentation depend on the substrate's structure and the individual's microbial community.

Lentils, oats, fruit and vegetables offer varied fibre sources. For athletes, distributing them across tolerable meals is generally more practical than a sudden large dose before competition. Added fibre in a bar alone does not replace varied plant foods.

WHO's general guidance for people older than 10 is at least 25 grams of naturally occurring dietary fibre per day. This is not a target to consume immediately before competition and does not establish that every athlete needs a fibre supplement. Actual intake belongs alongside adequate energy, tolerance and the whole eating pattern.

Increasing fibre works best with tolerable amounts, time to adapt and appropriate fluids. Suddenly adding several high-fibre products can cause bloating or altered bowel habits. The aim is a suitable combination of foods and timing; discomfort after one large serving is no reason to exclude every fibre source permanently.

Fibre and plant foods contribute to overall diet quality, but choices can change temporarily around competition. An athlete prone to digestive discomfort may choose a lower-fibre meal before intense exercise and eat higher-fibre foods at another time. Adjusting timing differs from excluding a food group in the long term.

Table references: NIDDK · 1 · NIH ODS · 2