What Type of Fibre is a Prebiotic? A Comprehensive Guide

December 2, 2025 •

2 min read

Prebiotics are non-digestible fibres that feed beneficial microbes in your gut, a key distinction from other forms of fibre. Not all dietary fibre is prebiotic, but specific types, including fructans and resistant starch, play a crucial role in nourishing your gut microbiome.

Quick Summary

Prebiotics are selective dietary fibres like inulin, FOS, GOS, and resistant starch that resist digestion and feed beneficial gut bacteria. Their fermentation supports the gut microbiome, producing health-promoting compounds and improving overall digestive health and immunity.

Key Points

Prebiotic vs. Regular Fibre: A prebiotic is a specific type of fermentable fibre that feeds beneficial gut microbes, unlike all other dietary fibre which aids general digestion.
Inulin and FOS: Inulin and fructo-oligosaccharides (FOS) are classic prebiotics belonging to the fructan family, found in chicory root, garlic, and onions, known for selectively boosting Bifidobacteria and Lactobacilli.
Resistant Starch: Resistant starch (RS) is a non-digestible starch that acts as a prebiotic, with types found in unripe bananas, and cooked and cooled starches, contributing to butyrate production.
GOS and Beyond: Galacto-oligosaccharides (GOS) from sources like legumes are another key prebiotic type, while others like pectin and beta-glucans also offer beneficial effects.
Varied Diet is Key: Consuming a wide variety of prebiotic-rich foods, including vegetables, legumes, and whole grains, is the best strategy to support a diverse and healthy gut microbiome.
Start Slowly: To prevent gastrointestinal discomfort like bloating, it is recommended to gradually increase your intake of prebiotic fibres.

Understanding Prebiotic Fibre

Fibre is a broad term for carbohydrates that the human body cannot fully digest. It comes in two main forms: soluble and insoluble. While both are vital for a healthy digestive system, not all fibre qualifies as a prebiotic. A prebiotic fibre is defined as a substrate selectively utilized by host microorganisms that confers a health benefit. This key difference lies in its fermentability by specific, beneficial gut bacteria, such as Bifidobacteria and Lactobacilli. In short, prebiotics are the food for your probiotics. They pass through the upper gastrointestinal tract largely intact and are fermented in the colon, producing short-chain fatty acids (SCFAs) that provide energy for colon cells and support overall health.

Key Types of Prebiotic Fibre

Inulin-Type Fructans (ITFs)

ITFs are a class of prebiotics found in many plants, consisting of chains of fructose units. This group includes both inulin and fructo-oligosaccharides (FOS).

Inulin: A longer-chain fructan, inulin is a soluble fibre abundant in chicory root, garlic, onions, leeks, and Jerusalem artichokes. It is known for promoting the growth of beneficial gut bacteria.
Fructo-oligosaccharides (FOS): A shorter-chain fructan found naturally in many of the same sources as inulin. It ferments relatively quickly in the gut.

Galacto-oligosaccharides (GOS)

GOS are oligosaccharides made primarily of galactose units. They are derived from lactose and found in legumes and dairy. GOS are effective at stimulating the growth of Bifidobacteria.

Resistant Starch (RS)

Resistant starch bypasses digestion in the small intestine and is fermented in the large intestine by gut bacteria, acting like dietary fibre. More details on resistant starch types and other potential prebiotics can be found on {Link: Springer https://link.springer.com/article/10.1007/s00253-022-12325-y}.

Comparison of Prebiotic Fibre Types

Consult {Link: Springer https://link.springer.com/article/10.1007/s00253-022-12325-y} for a comparison of prebiotic fibre types.

Incorporating Prebiotics into Your Diet

For information on incorporating prebiotics into your diet, including food sources and guidance on increasing intake, please refer to {Link: Springer https://link.springer.com/article/10.1007/s00253-022-12325-y}. You can also find information on {Link: ISAPP website https://isappscience.org/infographic-fiber-prebiotics/}.

Conclusion

A prebiotic is a specific type of fermentable fibre that fuels beneficial gut microorganisms, playing a critical role in gut and overall health. Examples include inulin-type fructans (inulin, FOS) from chicory and garlic, galacto-oligosaccharides (GOS) from legumes, and various forms of resistant starch found in starchy foods. Prebiotic fibre specifically nourishes the gut microbiome, leading to benefits like improved digestion and strengthened immunity. A diverse intake of prebiotic-rich whole foods supports a healthy internal ecosystem. For more information, refer to the International Scientific Association for Probiotics and Prebiotics (ISAPP)(https://isappscience.org/infographic-fiber-prebiotics/).

Frequently Asked Questions (FAQs)

Frequently Asked Questions

A prebiotic is a non-digestible food ingredient that selectively feeds beneficial gut bacteria, whereas a probiotic is a live microorganism, like the bacteria found in yogurt, that adds to the population of good bacteria in your gut.

No, not all dietary fibre is prebiotic. Only specific types of fermentable fibre that reach the colon and selectively stimulate the growth and activity of beneficial bacteria qualify as prebiotics.

Excellent food sources include chicory root, garlic, onions, Jerusalem artichokes, asparagus, unripe bananas, oats, and legumes like lentils and chickpeas.

Yes, some prebiotics like inulin and resistant starch can aid in weight management by increasing feelings of fullness and promoting the release of hormones that help regulate appetite.

Some individuals may experience temporary side effects like bloating, gas, or stomach cramps, especially with high doses. It is recommended to increase intake gradually.

Resistant starch bypasses digestion in the small intestine and travels to the large intestine, where it is fermented by gut bacteria, fueling them and producing beneficial compounds like butyrate.

SCFAs like butyrate, acetate, and propionate are produced when gut bacteria ferment prebiotic fibres. They are a primary energy source for colon cells, help lower inflammation, and contribute to metabolic health.