Fibers in Diet

Definition: Fiber refers to the roughage part of a plant structure that is not absorbable and thus its main action happens locally within the gut.

  • Benefits of fiber vary and can include helping digestion and elimination, increasing the sensation of fullness and helping with weight management, helping to control blood sugar and cholesterol, and preventing certain heart-related and digestive tract disorders.
  • The top 10 foods with a high fiber content include split peas, lentils, beans, figs, artichokes, acorn squash, green peas, raspberries, and strawberries.
  • Fiber fortified foods may not be a good source of fiber. Such foods do not provide enough fiber and some contain artificially made fiber such as methylcellulose, calcium polycarbophil, and wheat dextrin and should be avoided.
  • Fiber can be classified into different types based on its properties and chemical structure.

Soluble and Insoluble Fibers

One way to classify dietary fiber is based on the solubility of the fiber in water into soluble and insoluble. Most foods contain both soluble and insoluble fibers.

  • Soluble fiber is dissolvable in water and is fermented in the colon producing gas and active byproducts such as prebiotic and viscous etc. Soluble fiber slows down digestion and gastric emptying process giving a sensation of fullness long after eating.   Soluble fiber, through its action, helps regulate blood sugar and LDL cholesterol amongst others.
  • Insoluble fiber is not dissolvable in water and provides bulking which helps the defecation process, helping move waste through the intestines. Insoluble fiber may also help regulate blood sugar.
  • Both soluble and insoluble fibers increase food volume increasing the feeling of satiety without increasing calories. They both also help balance PH and help with intestinal fermentation and short-chain fatty acid production.

Types of Fiber

Some of the most common types of fibers based on their chemical structure include:

  • Cellulose/hemicellulose, insoluble fiber, found in wheat, rice, oat bran, nuts, etc., and acts as a natural laxative
  • Inulin/oligofructose, soluble fiber, is found in onions and can function as a prebiotic helping increase good bacteria growth in the gut.
  • Mucilage/beta-glucan, soluble fiber, found in oats, oat bran, legumes, barley, etc. may help reduce LDL cholesterol, reduce the risk of heart disease and type 2 diabetes, etc.
  • Pectin/gums, soluble and insoluble fiber, found in apple peel, fruits, berries seeds etc. may help slow the passage of food through the gut and help lower cholesterol
  • Resistant starch, soluble fiber, found in unripened bananas, oatmeal legumes etc. may help manage weight by increasing the sensation of satiety and insulin sensitivity thus helping control blood sugar levels
  • Others such as fibers added to processed foods include polydextrose, polyol thickeners, wheat dextrin, carrageenan, etc. with varying effects.

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