Recommended Daily Fiber Intake
Turns your daily calorie intake into a fiber target in grams using the IOM reference of 14 g per 1000 kcal, so 2000 kcal a day means 28 g.
Fibras (g/dia)
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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.
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Composite Modulus (Rule of Mixtures)
Calculate the longitudinal elastic modulus of a composite by the rule of mixtures, E_c = E_f·V_f + E_m·(1 − V_f), from the fiber modulus (E_f), the fiber volume fraction (V_f) and the matrix modulus (E_m). The result, in the modulus unit (GPa), is the modulus in the fiber direction (Voigt upper bound), assuming equal strain in fiber and matrix. It shows the composite stiffness is a volume-weighted average — stiff fibers (carbon, glass) at high fraction greatly raise the modulus. In the transverse direction, the inverse rule of mixtures (Reuss bound) applies, much lower. Enter the fiber modulus, the fiber fraction and the matrix modulus.
Edge Stress from Prestressing
Calculate the normal stress at an extreme fiber of a prestressed concrete section, σ = P/A + (P·e)/W, from the prestressing force P (MN), the section area A (m²), the tendon eccentricity e (m) and the section modulus W (m³). Prestressed concrete is one of the great structural engineering inventions of the 20th century: high-strength steel tendons are tensioned (prestressed) and anchored in the member, COMPRESSING the concrete before it even receives service loads. Since concrete is strong in compression but weak in tension, this pre-compression 'cancels' the tensions external loads would cause, allowing much longer spans and slenderer members than conventional reinforced concrete. The tendon is placed with ECCENTRICITY (below the centroid), so prestressing generates not only uniform compression (P/A) but also a moment (P·e) producing stresses opposite to the loading — compressing exactly the fiber that would tend to crack. This formula computes the resulting edge stress, summing axial compression and prestress bending; design verifies stresses stay within limits in all phases (at transfer, empty, and in service, loaded). Enter the prestressing force, area, eccentricity and section modulus.
Recommended Octane by Compression Ratio
Type the engine compression ratio and get the minimum octane band: below 9 takes 87, up to 10.5 takes 89-91, up to 12 takes 91-95, above that 95-98.
Draw-Down Ratio
Calculate an extrudate's draw-down ratio (DDR), DDR = (D_die ÷ D_product)², from the die orifice diameter D_die and the final product diameter D_product, as the ratio of cross-sectional areas. After leaving the die, the extrudate (a wire, tube, filament) is often PULLED and stretched by a haul-off at a speed higher than the exit speed, reducing its cross-section to the final size. The draw-down ratio is how much the section area is reduced. Drawing not only sets the final size but ORIENTS the molecular chains in the pull direction, which can greatly increase the product's mechanical strength in that direction (used in oriented fibers, tapes and films, far stronger than unoriented material). The draw-down ratio, combined with die swell, sets the relation between orifice size and final product. There are limits: excessive drawing can break the extrudate or cause defects. It is a key parameter in making fibers, monofilaments, small-diameter tubes and wire coating. Enter the die diameter and the final product diameter.
Paper Tear Index
Compute the paper tear index, index = tear force (mN) / grammage (g/m²), in mN·m²/g, normalizing the tear resistance by the grammage. Tearing depends greatly on fiber length (long fibers resist more) — which is why packaging papers use long softwood fibers. It is a property that often competes with tensile (more refining raises tensile but lowers tear). Enter the tear force and the grammage.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.