Fibre is the indigestible part of food. They are categorised as soluble, insoluble and resistant starch fibres; all of which are required to support a healthy digestive system as well as a healthy immune system.

Soluble fibre absorbs water, turning into a gel during digestion. It slows digestion down by increasing the time it takes to empty the stomach’s contents, resulting in us feeling fuller for longer. It also assists in lowering cholesterol and regulating blood sugar levels.

Insoluble fibre absorbs water; its role is to soften the bowel contents, softening the stool or poo, making it easier to go to the toilet and promotes regular bowel movements.

Resistant starches are prebiotics that cannot be digested in the small intestine. Once they move to the large intestines however, fermentation takes place and this supports the production of probiotics, the good bacteria, which enhances bowel function and supports immune health.

About 70–80% of your immune cells reside in the gut, closely interacting with the gut microbiome, which is why fibre is so incredibly important to gut health. The gut lining and its microbes serve as the primary defense—the body’s first line of protection against pathogens.

The connection? Fiber = Prebiotics = Fuel for Good Bacteria

• Fiber acts as a prebiotic, feeding beneficial gut bacteria like Bifidobacteria and Lactobacilli

• These microbes ferment fiber to produce short-chain fatty acids (SCFAs) such as butyrate, acetate, and propionate

• Diets rich in fermentable fiber strengthen the gut barrier, reduce infection risk, and support respiratory & skin immunity

• A clinical study showed fiber and fermented food diets each uniquely boosted microbiome diversity and immune markers.

Sources of fermentable fiber?

Legumes & Beans

• Lentils, chickpeas, black beans, kidney beans — Packed with resistant starch and soluble fiber; 12–18?g fiber per cooked cup.

Whole Grains

• Oats & barley — Rich in beta?glucan, a soluble fermentable fiber that supports gut bacteria .

• Quinoa, brown rice — Provide additional fermentable fiber for microbiome diversity.

Fruits

• Apples, pears, bananas (especially unripe) — High in pectin or resistant starch, which feed beneficial microbes.

• Berries (raspberries, blackberries) — Contain soluble fiber and antioxidants.

Vegetables

• Onions, garlic, leeks, asparagus, Jerusalem artichoke, artichoke hearts — Rich in inulin, fructooligosaccharides (FOS), and other fermentable fibers.

Nuts & Seeds

• Flaxseeds, chia seeds, almonds — Offer soluble fiber and mucilage that feed gut bacteria.

Roots & Other

• Chicory root, dandelion greens, jicama, burdock root, konjac, yacon — Exceptional sources of inulin, FOS, and other prebiotics.

• Seaweed — Contains unique polysaccharides stimulating Lactobacillus & Bifidobacteria growth.

Quick Ways to Add Fermentable Fiber:

• Start with oatmeal topped with chia, flax, and berries.

• Toss beans or lentils into soups, salads, curries.

• Mix raw garlic, onions, and leeks into dressings or stir-fries.

• Snack on apples or pears, and try unripe bananas in smoothies.

• Roast artichokes or sauté asparagus as sides.

• Add jerusalem artichoke or chicory powder to coffee.