Fibers

Dietary fiber is a plant-based nutrient and a type of carbohydrate, unlike other carbs, it cannot be broken down by the human digestive system into digestible sugar molecules. Fiber passes through the intestinal tract relatively intact.

Fiber is important to digestion and regularity, weight management, blood sugar, cholesterol maintenance and it is linked to longevity and decreasing the risk of diseases.

Fiber can be put into two categories: soluble and insoluble fiber. Plant-based foods contain both soluble and insoluble fiber. Soluble fiber, such as pectin, gum, and mucilage, dissolves in water; insoluble fiber, such as cellulose and lignin, do not. In the body, soluble fiber dissolves and becomes a gel-like substance. Insoluble fiber mostly retains its shape while in the body.

Soluble fiber helps to decrease blood glucose (blood sugar) levels. It also helps lower blood cholesterol. Insoluble fiber speeds up the passage of food through the digestive system. This helps maintain regularity and prevent constipation. It also increases fecal bulk, which makes stools easier to pass.

Solvable fiber

Unsolvable fiber

The difference is found in the chemical structure (open or closed) which makes the fiber solvable or not. Fibers do play an important role in relation to function in age control. Fiber-rich diets show to give a better control of the gut flora. This gut flora is one of the first parts of the body which degenerate while aging. In current knowledge, it is not yet established how it happens but the first part of aging starts with a malfunctioning of digestion intake. When building materials (the mentioned other food parts) are not digestively prepared for uptake the body is no longer able to recover and restore damaged tissues, nor has the energy to fight diseases.  This is the main area fibers are active. in.

The effects of fibers on health are;

• Digestive aid – there is a need for fibers to keep the liquids inside the system so that “water” can be trapped and used to fill the colon and intestine. Both muscular based organs need to have a “grip” on foods to let them pass, even against gravity, from the mouth into the bloodstream. All food is guided by the muscular movements of the digestive system. Fibers fill the foods until they are easier to transport.
• Bacteria in the digestive tract need food and foundation. Fibers can be used as vehicle and food. Bacteria look for fibers to settle down and do their part of work in the digestive system such as fermentation.
• Fibrin fibers are the most stretchable known fibers existing (be stretched to 4.3 times their length before breaking) in nature are important to our blood. They play a strong role in blood clotting but also in heart functions (attacks and strokes). Blood clots are a three-dimensional network or mesh of fibrin fibers, stabilized by another protein called factor XIIIa. Fibrin fibers measure about 100 nanometers in diameter, roughly 1,000 times smaller than a human hair.
• Elastic skin fibers are synthesized by fibrocytes. These fibers are capable of extension to approximately twice their length at rest. In contrast to collagen bundles, elastic fibers are wavy and branching. Elastic fibers in the papillary dermis are present either as bundles of microfibrils, oxytalan fibers or as cross-linked elastin on one hand or as elaunin fibers on the other. In the reticular dermis, elastic tissue appears mainly as elastin. The elastic fiber is formed from the elastic microfibril (consisting of numerous proteins such as microfibrillar-associated glycoproteins, fibrillin, fibulin, and the elastin receptor) and amorphous elastin.
• Resistant starch (RS) is a form of starch that resists digestion in the small intestine and, as such, is classified as a type of dietary fiber. RS can be categorized as one of five types (RS1–5), some of which occur naturally in foods such as bananas, potatoes, grains and legumes and some of which are produced or modified commercially, and incorporated into food products.
• RS‐rich foods may be particularly useful for managing diabetes. Dietary fiber is almost universally defined as the material isolated by methods approved by the Association of Official Analytical Chemists (AOAC). Older AOAC methods measured non‐starch polysaccharides (NSP), lignin, some inulin and some resistant starches and non‐digestible oligosaccharides, but not all (Prosky et al. 1988; Lee et al. 1992). There are five types of RS.
• RS1 – inaccessible to digestive enzymes due to the physical barriers formed by cell walls and protein matrices. Less resistant to digestion compared with other types.
• RS2 – starches protected from digestion due to their crystalline structure.
• RS3 – retrograded starch formed when starchy foods (e.g. potatoes, pasta) are cooked then cooled. Long‐branched chains of amylopectin form double helices that cannot be hydrolyzed by digestive enzymes.
• RS4 – chemically modified starch formed by cross‐linking, etherization or esterification.
• RS5 – two different components have been proposed as RS5. The first comprises amylose-lipid complexes, which either form during processing and reform after cooking or can be created artificially and added to foods (Seneviratne & Biliaderis 1991; Hasjim et al. 2010, 2013; Lau et al. 2016). The second is resistant maltodextrin, which is processed to purposefully rearrange starch molecules (Mermelstein 2009). The majority of publications describe RS5 as amylose-lipid
• Amylose is digested slowly, whereas amylopectin is digested rapidly. Resistant starch and gut health RS has been noted to increase the production of SCFA in the gut and also to modulate the composition of gut microbiota, but there appears to be significant inter-individual variation in responses and health implications of these changes remain to be elucidated.

Resistant starch and glucose metabolism

There is good evidence that postprandial glycemic responses to RS are reduced compared to digestible carbohydrates. As such, there is an approved health claim in the EU stating that baked products containing at least 14% RS in place of digestible starch reduce postprandial glycemia. There may be synergism between RS and other fiber types in reducing glycemic responses.

Different types of fibers for human consumption

Cellulose	E 460	cereals, fruit, vegetables (in all plants in general)
Chitin	—	in fungi, the exoskeleton of insects and crustaceans
Hemicellulose		cereals, bran, timber, legumes
Hexoses	—	wheat, barley
Pentose	—	rye, oat
Lignin	—	stones of fruits, vegetables (filaments of the garden bean), cereals
Xanthan gum	E 415	production with Xanthomonas-bacteria from sugar substrates
Resistant Starch		Can be starch protected by seed or shell (type RS1), granular starch (type RS2) or retrograded starch (type RS3)
Resistant Starch	—	high amylose corn, barley, high amylose wheat, legumes, raw bananas, cooked and cooled potatoes etc.
water-soluble dietary fibers
Arabinoxylan (a hemicellulose)	—	psyllium[13]
Fructans		replace or complement in some plant taxa the starch as a storage carbohydrate
Inulin	—	in diverse plants, e.g. topinambour, chicory, etc.
Polyuronide
Pectin	E 440	in the fruit skin (mainly apples, quinces), vegetables
Alginic acids (Alginates)	E 400–E 407	in Algae
Sodium alginate	E 401
Potassium alginate	E 402
Ammonium alginate	E 403
Calcium alginate	E 404
Propylene glycol alginate (PGA)	E 405
agar	E 406
carrageen	E 407	red algae
Raffinose	—	legumes
Xylose	—	monosaccharide, pentose
Polydextrose	E 1200	synthetic polymer, ca. 1kcal/g
Lactulose	—	synthetic disaccharide

Conclusion; Fibers do have a wide range of functions in the body. It must be clear that there is a distinction between pure carbohydrate constructed fibers and fiber networks made of proteins when we define the right group of fibers.