Fiber Explained

Written by Mindy Antimie

This article first appeared on

It seems strange that humans are encouraged to eat a high fiber diet. Why do we need to eat something that we can’t digest or absorb? Although human cells can’t digest or absorb fiber, the nutrient has cunningly found a way to be an essential predictor for health. Fiber provides numerous benefits including lowering blood glucose, lowering LDL cholesterol, producing satiety hormones, and increasing stool bulk. Let’s dig into what fiber is, why we need fiber, and how it accomplishes these feats.

A high fiber diet is essentially a diet composed of a wide variety of fruits, vegetables, nuts, seeds, legumes, bran, and other plant foods. A high fiber diet is a diet that is high in plant foods, which offer numerous benefits regardless of the fiber component. You can find the recommended intake of dietary fiber for your age group on the website.

9 Types of Fiber in Foods


  • Foods that contain lignin: flaxseeds, fruit with edible seeds like strawberries, wheat/bran, carrots, and other root vegetables     
  • Special case in that it is not a carbohydrate, is the major structural component of woody plants (like celery) and seeds
  • Made of polyphenol polymers
  • Insoluble
  • Poorly fermentable


  • Foods that contain cellulose: bran, legumes, vegetables, apples, nuts 
  • The main component of plant cell walls
  • Made of glucose units
  • Insoluble
  • Poorly fermentable


  • Foods that contain hemicellulose: bran, nuts, legumes
  • A component of plant cell walls
  • Made of xylose, mannose, galactose, arabinose, glucuronic acid, glucose, and rhamnose
  • May be insoluble or soluble depending on the configuration of the sugars
  • May be fermented or poorly fermented depending on the configuration of the sugars


  • Foods that contain pectin: apples, legumes, citrus, nuts, and legumes     
  • Forms part of the cell wall in plants and part of the middle lamella which connects plant cells together
  • Made of mostly galacturonic acid with occasional rhamnose, arabinose, xylose, fucose, and galactose attached
  • Soluble
  • Fermentable


  • Foods that contain gums: oatmeal, barley, legumes
  • Forms the substance that plants secrete in response to injury
  • Made of mostly galactose and mannose
  • Soluble
  • Fermentable


  • Foods that contain Beta-Glucans: oats, barley, some mushrooms·     
  • Is found in the cell walls of some fungi and plants
  • Made of beta-D-glucopyranosyl units
  • Soluble
  • Fermentable

Fructans (inulin, oligofructose, and fructooligosaccharides)

garlic on stainless steel bowl
tomatoe lot
  • Foods that contain fructans: chicory, asparagus, leeks, onions, garlic, tomatoes, bananas     
  • Can be the means of storing energy in the plant
  • Made of fructose
  • Soluble
  • Fermentable

Resistant Starch

yellow bananas
  • Foods that contain resistant starch: legumes, bananas 
  • Found in plant cell walls
  • Made of long amylose chains (starch)
  • Soluble
  • Fermentable


What is Psyllium Husk? Its Uses and When NOT to Take It
Photo courtesy of Super Food Evolution
  • Foods that contain psyllium: husk of psyllium seeds
  • This is a functional fiber found in the outer part of psyllium seeds
  • Is a mucilage made of arabinose and xylose
  • Soluble
  • Poorly fermented

It should be noted that I did not cover the functional fibers: chitin, dextrin, polydextrose, or galactooligosaccharides.

Keep Reading on More Types of FIBER! —>

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