'Fiber' in the nutritional sense refers to 'dietary fiber'. Dietary fiber includes the indigestible parts of the plant foods we eat. Fiber originates in structure of plant cells, such as cell walls. As plants foods are chewed and subsequently digested, plant cells are broken down allowing their nutrients to be absorbed while fiber collects and is left behind in the digestive tract to be eliminated later. As fiber is being eliminated, it 'scours' the digestive tract of undigested food and debris, helping to promote healthy elimination. Some types of fiber can also absorb excess dietary fats and cholesterol, allowing them to be eliminated.
Animal foods contain no fiber.
Soluble vs Insoluble Fiber: You Need Both
There are two principal types of dietary fiber: soluble and insoluble, each playing a complementary role in digestive health.
- Soluble fiber attracts water and excess dietary fats, forming bulk and retaining moisture in the digestive tract. Soluble fiber can slow the rate at which calories are absorbed, which has a favorable impact on blood sugar levels and body composition. Soluble fiber is found in the soft part of fruits, peas, oats, barley, etc.
- Insoluble fiber is non-absorbent. It cleanses and adds bulk to the system, scouring the walls of the digestive tract and promoting effective elimination. Insoluble fiber is found primarily in fruit and vegetable peels, and seed hulls.
Fiber's Multiple Health Benefits
Fiber is needed for proper and consistent elimination of harmful wastes. Fiber is particularly important for those with elevated blood lipids like cholesterol. Research has shown that adequate consumption of soluble fiber may lower cholesterol levels over time. Soluble fiber may also improve glucose tolerance in those with diabetes.
Using Fiber Supplements
Fiber supplements are available as capsules, tablets, liquids and powders. Fiber supplements may contain on or more types of fiber. The most common fiber ingredients are psyllium husks, flaxseed meal, bran, and pectins. Fiber supplements often contain other ingredients like laxatives or herbs that soothe the digestive tract. Follow manufacturer's direction closely since fiber supplements vary in composition. Drink plenty of water when using fiber supplements. General adult recommended daily intake of fiber is a minimum of 25-35 grams.
Side-effects and Cautions:
Temporary gas and bloating can occur anytime dietary fiber intake increases or decreases significantly. Use of fiber supplement may slow or reduce the absorption of certain medications.