2026: The Year of Fibre – What Fibre Really Is

Part One of the Fibre Series

Welcome to part one of the fibre series, Balkin Nutrition’s deep dive into one of the most fascinating nutrients in human health. In this series, we will examine the biology of fibre, how it shapes the gut microbiome, and the surprising ways it can influence metabolism, hormones, and overall health. Along the way, we’ll uncover the science behind fibre, reveal why diversity matters more than just quantity, and offer insights that may change the way you think about this humble nutrient.

Fibre is often described simply as “roughage,” something to keep digestion moving. But in reality, it’s far more than that. Fibre is a complex carbohydrate that resists digestion in the small intestine, yet it plays a crucial role in feeding your gut microbes, producing important signalling molecules, and supporting metabolic and immune functions [1,2].

Fibre at the Macro Level

Traditionally, fibre is grouped into soluble and insoluble forms:

• Soluble fibre dissolves in water and forms gels (for example, oats, legumes, psyllium).

• Insoluble fibre resists water, adds bulk to stool, and supports regularity (for example, wheat bran, vegetable skins).

While this is a useful starting point, modern research looks at fibre in a broader way, including its:

• Fermentability – how easily gut microbes can break it down.

• Viscosity – whether it forms gels that slow digestion.

• Physiological effects – how it influences metabolism, immunity, and gut health [2].

In short, fibre isn’t just one ingredient; it’s many components acting together to influence your body at multiple levels.

Fibre at the Micro Level

At a molecular level, fibre is made up of polysaccharides, long chains of sugar molecules that our enzymes cannot digest [3]. Different types of fibre behave differently in the gut:

• Cellulose – straight-chain glucose; adds bulk; poorly fermented.

• Hemicellulose – mixed sugars; partially fermentable; supports a variety of microbes.

• Pectins – found in fruit; highly fermentable; help regulate cholesterol and glucose.

• Beta-glucans – oats and barley; gel-forming; improve insulin sensitivity [4].

• Resistant starch – escapes digestion; fermented into short-chain fatty acids [5].

Different fibres support different microbes in the gut, which in turn affects the kinds of molecules they make.

Why Fibre Matters

Once fibre reaches the colon, it is fermented by gut microbes into short-chain fatty acids (SCFAs) such as butyrate, propionate, and acetate [6]. These SCFAs act as messengers, linking your gut to organs including the liver, brain, and immune system. Fibre doesn’t just support digestion, it helps regulate hormones, metabolism, and immune responses.

Not all fibre is the same, and not all fibres are equally beneficial. Modern diets are often low in both fibre quantity and diversity, which can reduce microbial variety and limit the beneficial effects of fibre [2]. Think of fibre as a portfolio; the more varied it is, the better your body can thrive.

What’s Coming in This Fibre Series

Over the coming weeks, we’ll take a closer look at fibre from every angle. We’ll explore how different fibres interact with your gut microbes, the role of short-chain fatty acids as metabolic messengers, and the ways fibre can influence hormones, inflammation, and overall health. We’ll also uncover why variety matters more than simply counting grams, and how whole-food sources differ from isolated fibres.

Next week, we’ll dive into fibre and the gut microbiome, exploring which fibres feed which microbes, and how these interactions can shape your metabolism and overall wellbeing.

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References:

1. Slavin JL. Dietary fibre and body weight. Nutrition. 2013;29(4):411–418.

2. Makki K, Deehan EC, Walter J, Bäckhed F. The impact of dietary fibre on gut microbiota in host health and disease. Cell Host & Microbe. 2018;23(6):705–715.

3. Anderson JW, Baird P, Davis RH, et al. Health benefits of dietary fibre. Nutrition Reviews. 2009;67(4):188–205.

4. Brown L, Rosner B, Willett W, Sacks FM. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr. 1999;69(1):30–42.

5. Birt DF, Boylston T, Hendrich S, et al. Resistant starch: promise for improving human health. Adv Nutr. 2013;4(6):587–601.

6. Koh A, De Vadder F, Kovatcheva-Datchary P, Bäckhed F. From dietary fiber to host physiology: short-chain fatty acids as key bacterial metabolites. Cell. 2016;165(6):1332–1345.