Dietary fibre comes entirely from plant foods — vegetables, fruit, legumes, wholegrains, nuts, and seeds. It falls into two broad types: soluble fibre (oats, barley, legumes, psyllium) forms a gel in the gut that slows glucose absorption and lowers LDL cholesterol. Insoluble fibre (wheat bran, wholegrain foods, many vegetables) adds bulk and speeds transit time, supporting regularity.
Most adults need 25–30 g of fibre per day; most fall well short. A high-fibre diet is consistently associated with lower risk of heart disease, type 2 diabetes, colorectal cancer, and all-cause mortality. Most of this benefit appears to come from food sources rather than supplements.
Increasing fibre intake gradually and drinking adequate water reduces the bloating and gas that can accompany a sudden increase. If you have IBS, some high-fibre foods may worsen symptoms — a low-FODMAP approach may help.