Fiber: why and how much

Soluble fiber (pectin, beta-glucan, gum) dissolves in water to form a viscous gel. It's found in oats, barley, apples, citrus fruits, and legumes. It slows digestion, stabilizes blood sugar, and helps reduce LDL cholesterol.

Insoluble fiber (cellulose, lignin) doesn't dissolve and acts like an "intestinal broom." Present in wheat bran, leafy greens, and seeds, it speeds up transit, increases stool volume, and prevents constipation.

A varied diet naturally provides both types. It is not necessary to calculate the soluble/insoluble ratio: by eating vegetables, fruit, whole grains, and legumes every day, you cover both categories.

Fiber is the main food source for beneficial bacteria in your gut. By fermenting them, these bacteria produce short-chain fatty acids (butyrate, propionate, acetate) that nourish gut wall cells and reduce inflammation.

A diverse microbiota is associated with better immunity, a more efficient metabolism, and even better mental health via the gut-brain axis. The diversity of fiber consumed is as important as the quantity: vary your sources to feed different bacterial strains.

Prebiotics, a specific type of fermentable fiber (inulin, FOS), are particularly beneficial. They are found in onions, garlic, leeks, asparagus, slightly green bananas, and chicory.

Among legumes, white beans top the list (7 g/100 g cooked), followed by lentils (8 g), chickpeas (6 g), and split peas (8 g). These are the most concentrated and economically accessible sources.

Regarding grains, oat bran (15 g/100 g), rolled oats (10 g), and whole rye bread (8 g) are excellent options. Quinoa (3 g) and brown rice (2 g) round out the intake.

For fruits and vegetables, raspberries (7 g), pears with skin (5 g), artichokes (5 g), and broccoli (3 g) are among the best. Chia seeds (34 g/100 g) and flaxseeds (27 g) are easy fiber boosters to add to yogurt and smoothies.