Fibra Diária Recomendada

Daily fiber: how much, and which kind

The Institute of Medicine (IOM) puts adequate intake at 25 g/day for women and 38 g/day for men, which works out to about 14 g per 1,000 kcal you eat. Brazilian guidelines (SBC, SBD) ask for ≥25 g/day in adults. Take a 2,200 kcal diet as an example: 14 × 2.2 ≈ 31 g of fiber/day. There are two kinds worth knowing. Soluble fiber (oats, apple, beans, psyllium) turns to gel in the gut and brings down LDL cholesterol and post-meal glucose. Insoluble fiber (leafy greens, wheat bran, whole grains) adds bulk to stool and moves things along, which is what helps with constipation. The average Brazilian eats <20 g/day, well short of the goal. When you do ramp up, do it slowly and drink plenty of water so you don't end up bloated.

Applications: preventive nutrition, diabetes, cardiovascular disease, gastroenterology

Getting enough fiber matters across a lot of areas. In preventive nutrition it ties into colorectal cancer prevention. For type 2 diabetes it slows glucose absorption and improves HbA1c. In cardiovascular disease the soluble kind lowers LDL, while in chronic constipation the insoluble kind plus hydration does the work. It also supports weight control through satiety per kcal, and feeds the gut microbiota as a substrate for short-chain fatty acid production. You'll see it in protocols for IBS-C, diverticulosis and metabolic syndrome.

FAQ

Can I get all my fiber from supplements? Better not to. Whole foods come with micronutrients and polyphenols that a supplement won't give you. Save psyllium or inulin for closing a gap, not replacing meals.

Does fiber interfere with medications? It can. Psyllium and other soluble fibers may cut the absorption of levothyroxine, metformin and certain antibiotics, so leave 1–2 hours between the fiber and the dose.

I increased fiber and got bloated. What now? Back off and add only about 5 g per week, drink 30–35 mL/kg of water, and keep soluble and insoluble in balance. Jumping from 10 g to 30 g in a single day is what brings on the gas and discomfort.