Two kinds, two jobs
Soluble fibre (oats, beans, apples, psyllium) forms a gel that slows sugar absorption and binds cholesterol. Insoluble fibre (whole grains, vegetable skins, nuts) adds bulk and keeps digestion regular.
Your gut microbiome eats it
Gut bacteria ferment fibre into short-chain fatty acids like butyrate, which nourish the cells lining your colon and help regulate inflammation and appetite signalling.
How much you need
Around 25g a day for women and 38g for men. Adding it gradually with plenty of water avoids the bloating that makes people give up in week one.