What is Natural Dietary Fiber?
Natural dietary fiber is dietary fiber naturally present in the food or extracted from natural foods and added to other foods to increase their fiber content. In the later case it is called functional fiber.
The aim of this article is to collect common fiber-related terms rather than make you anxious about which types of fiber you should include into your diet.
Some components of natural fiber, like mucilage, pectin and gum are soluble in water. When ingested, they absorb water and make stool bulky and can thus prevent both constipation and mild diarrhea. Chemically, they are complex carbohydrates and glycoproteins that can not be digested and have no calorie value. Normal colonic bacteria can partly break them down and yield substances beneficial for the cells that line the colonic wall. During bacterial breakdown (fermentation) some gas is usually produced.
Pectin and gum are also used in food production as thickening or gelling agents, stabilizers, or emulsifiers.
Mucilage is a thick, viscous substance, partly soluble in water. It is composed from edible but non-digestible proteins and polysaccharides. Plants containing mucilage:
- Flax seed
- Psyllium husk
- Aloe vera
- Liquorice root
- Chia seeds
- Basela alba (Malabar spinach)
- Chinese (Japanese, Korean) Yam
Pectin is soluble indigestible carbohydrate, found in:
- Citrus fruits: orange, grapefruit
- Kaopectate®, Pepto-Bismol®, anti-diarrheal drug
- Various fiber supplements
It is an ingredient in a gelling sugar (Jam Sugar) used in home made jams and as a thickener in many commercial foods. Pectin helps to lower LDL cholesterol by binding bile acids and cholesterol from the food in the intestine.
Natural gum is soluble dietary fiber found in wooden parts of plants and seed coatings.
- Gum arabic (E414 on food product labels) is produced from a hardened sap (fluid) of acacia tree. It is used in soft drink syrups, gummy candies and edible glitter (used in cake decoration).
- Dammar gum is produced from an endosperm of seeds of certain trees found in India. It is used as glazing agent giving foods a shiny appearance.
- Guar gum (E412) is obtained from the endosperm of guar bean seeds.
- Locust been gum or carob gum is extracted from the seeds of Carob tree.
Xanthan gum is a corn starch-like carbohydrate derived from corn sugar and processed by fermentation by Xanthomonas campestris bacteria. It is therefore not a trully natural fiber.
Beta-glucan is soluble or insoluble fiber found in barley and oats and is often added to other foods to increase their fiber content. It consists from mollecules of glucose. Beta-glucan can lower LDL cholesterol (1).
Glucomannan is a soluble fiber derived from the tubers of Amorphophallus konjac plant.
Agar (agar-agar) is a gelatinous substance derived from marine algae (seaweed); it contains soluble fiber. It is mostly used in certain Japanese deserts.
Cellulose is a chain of glucose molecules. It can not be digested by human body and also not broken down by friendly intestinal bacteria, so it does not yield gas. It is not soluble in water.
Hemicellulose is composed from glucose, galactose and other sugars. Some types may be soluble in water and broken down by intestinal bacteria.
Cellulose and hemicellulose give bulk to the stool and speed up the passage of food through the gut. They can be found in large amounts in:
- Bran and whole grains
- Roots (beetroot)
- Apple and pear skin
- Fiber supplements, like Unifiber®
Lignin is composed from phenoles and is insoluble in water. It is not digestible or broken down by intestinal bacteria. It acts as an antioxidant. Lignin can be found in:
- Root vegetables
- Flax seed
- Berries’ seeds
- Green beans
- Whole grains
Resistant starch is a form of starch that can not be digested. It is insoluble. Normal colonic bacteria break it down and form short chain fatty acids, which are beneficial for colonic mucosal cells. Resistant starch can be found in:
- Navy beans
- Unripe bananas
- Cold potatoes
- Cold pasta
- Wholegrain bread
- Fiber supplements, like Hi-maize®
- Beta-glucan can lower LDL cholesterol (nih.gov)