Dietary fiber
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Reverted edits by [[Special:Contributions/198.184.16.247|198.184.16.247]] ([[User talk:198.184.16.247|talk]]) to last version by Octahedron80
'''Dietary fibers''' are the indigestible portion of plant foods that move food through the [[digestive system]], absorbing water and easing [[defecation]]. Dietary fiber consists of non-[[starch]] [[polysaccharide]]s such as [[cellulose]] and many other plant components such as [[dextrin]]s, [[inulin]], [[lignin]], [[wax]]es, [[chitin]]s, [[pectin]]s, beta-[[glucans]] and [[oligosaccharide]]s. The term "fiber" is somewhat of a misnomer, since many of the so-called dietary fibers are not [[fiber]]s at all. The term has largely taken over the role of the older term "roughage".
== Soluble and insoluble fibers==
Sources of dietary fiber are usually divided according to whether they are water-soluble or not. Both types of fiber are present in all plant foods, with varying degrees of each according to a plant’s characteristics. Insoluble fiber possesses passive water-attracting properties that help to increase bulk, soften stool and shorten transit time through the [[intestinal tract]]. Soluble fiber undergoes metabolic processing via [[fermentation (biochemistry)|fermentation]], yielding end-products with broad, significant health effects.
For example, [[plum]]s (or [[prune (fruit)|prune]]s) have a thick skin covering a juicy pulp. The plum's skin is an example of an insoluble fiber source, whereas soluble fiber sources are inside the pulp.<ref>Stacewicz-Sapuntzakis M, Bowen PE, Hussain EA, Damayanti-Wood BI, Farnsworth NR. Chemical composition and potential health effects of prunes: a functional food? Crit Rev Food Sci Nutr. 2001 May;41(4):251-86.[http://www.ncbi.nlm.nih.gov/pubmed/11401245]</ref> Other sources of insoluble fiber include [[whole wheat]], [[wheat]] and [[corn]] [[bran]], [[flax seed]] [[lignans]] and [[vegetables]] such as [[celery]], [[nopal]], [[green bean]]s, [[potato]] skins and [[tomato]] [[peel (fruit)|peel]].<ref>Alvarado A, Pacheco-Delahaye E, Hevia P. Value of a tomato byproduct as a source of dietary fiber in rats. Plant Foods Hum Nutr. 2001;56(4):335-48.[http://www.ncbi.nlm.nih.gov/pubmed/11678439]</ref>
==Fermentable fiber==
The American Association of Cereal Chemists defined soluble fiber this way:
''“the edible parts of plants or similar carbohydrates resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine.”''<ref>http://www.aaccnet.org/DietaryFiber/pdfs/dietfiber.pdf</ref>
There are several key words in this statement that invite analysis and comment for considering fermentable fiber.
''edible parts of plants'' — indicates that some parts of a plant we eat — skin, pulp, seeds, stems, leaves, roots — contain fiber. Both insoluble and soluble sources are in those plant components.
''carbohydrates'' — complex carbohydrates, such as long-chained sugars also called [[starch]], [[oligosaccharides]] or [[polysaccharides]], are excellent sources of soluble fermentable fiber.
''resistant to digestion and absorption in the human small intestine'' — foods providing nutrients are digested by [[gastric acid]] and [[digestive enzymes]] in the stomach and small intestine where the nutrients are released then absorbed through the intestinal wall for transport via the blood throughout the body. A food resistant to this process is undigested, as insoluble and soluble fibers are. They pass to the large intestine only affected by their absorption of water (insoluble fiber) or dissolution in water (soluble fiber).
''complete or partial '''fermentation''' in the large intestine'' — the large intestine comprises a segment called the [[Colon (anatomy)|colon]] within which additional nutrient absorption occurs through the process of fermentation. Fermentation occurs by the action of colonic bacteria on the food mass, producing gases and short-chain fatty acids. It is these short-chain fatty acids — [[butyric acid|butyric]], [[acetic acid|ethanoic]] ([[acetic]]), [[propionic acid|propionic]], and [[valeric acid|valeric]] acids — that scientific evidence is revealing to have significant health properties.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&cmd=Retrieve&dopt=abstractplus&list_uids=16633129 Colonic health: fermentation and short chain fatty...[J Clin Gastroenterol. 2006] - PubMed Result<!-- Bot generated title -->]</ref>
To summarize<ref>Tungland BC, Meyer D, Nondigestible oligo- and polysaccharides (dietary fiber): their physiology and role in human health and food, Comp Rev Food Sci Food Safety, 3:73-92, 2002 (Table 3)[http://webdev.ift.org/NR/rdonlyres/7F1901F3-743E-4C1A-8A3A-38473B8A1037/0/crfsfsv01n3p073077ms20001598.pdf]</ref>,
fiber components with partial or low fermentability are
* [[cellulose]], a [[polysaccharide]]
* [[hemicellulose]], a polysaccharide
* [[lignan]]s, a group of [[phytoestrogen]]s
* plant [[wax]]es
* [[resistant starch]]es
Fiber components with high fermentability are
* [[beta-glucans]], a group of polysaccharides
* [[pectin]]s, a group of [[heteropolysaccharide]]s
* [[natural gum]]s, a group of polysaccharides
* [[inulin]]s, a group of polysaccharides
* [[oligosaccharide]]s, a group of short-chained or [[simple sugar]]s
==Short-chain fatty acids==
[[Short chain fatty acid]]s are used by the intestinal [[mucosa]] or absorbed through the colonic wall into the [[portal circulation]] (supplying the [[liver]]) that transports them into the general [[circulatory system]]. Particularly, [[butyric acid]] has extensive physiological actions that promote health effects, among which are:
* Stabilizes blood [[glucose]] levels by acting on pancreatic [[insulin]] release and liver control of [[glycogen]] breakdown
* Suppresses [[cholesterol]] synthesis by the liver and reduces blood levels of [[Low-density lipoprotein|LDL cholesterol]] and [[triglycerides]] responsible for [[atherosclerosis]]
* Lowers colonic [[pH]] (i.e., raises the acidity level in the [[Colon (anatomy)|colon]]) which protects the lining from formation of [[colonic polyps]] and increases absorption of [[dietary minerals]]
* Stimulates production of [[T helper cells]], [[antibodies]], [[leukocytes]], [[cytokines]] and [[lymph]] mechanisms having crucial roles in [[immune]] protection
* Increases proliferation of colonic bacteria beneficial for intestinal health — [[Bifidobacteria]] and [[Lactobacilli]] (serving a [[probiotic]] function)
* Improves barrier properties of the colonic [[mucosal]] layer, inhibiting [[inflammatory]] and [[adhesion]] irritants
Summarizing these effects, fermentable fibers yield the important short-chain fatty acids that affect blood glucose and lipid levels, improve the colonic environment and regulate immune responses.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16870803&query_hl=1&itool=pubmed_docsum Short-chain fatty acids: ready for prime time? [Nutr Clin Pract. 2006] - PubMed Result<!-- Bot generated title -->]</ref><ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17311984&query_hl=14&itool=pubmed_docsum Prebiotics, probiotics, and synbiotics affect mine...[J Nutr. 2007] - PubMed Result<!-- Bot generated title -->]</ref>
==Regulatory guidance on fiber products==
{{Globalize/North America}}
On average, North Americans consume less than 50% of the dietary fiber levels required for good health. In the preferred food choices of today's youth, this value may be as low as 20%, a factor considered by experts as contributing to the [[obesity]] crisis seen in many [[developed countries]].<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17236437&query_hl=2&itool=pubmed_docsum The 'skinny' on childhood obesity: how our western...[Pediatr Ann. 2006] - PubMed Result<!-- Bot generated title -->]</ref><ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17130861&query_hl=2&itool=pubmed_docsum PubMed Result<!-- Bot generated title -->]</ref><ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16596802&query_hl=2&itool=pubmed_docsum Carbohydrates and dietary fiber. [Handb Exp Pharmacol. 2005] - PubMed Result<!-- Bot generated title -->]</ref>
Recognizing the growing scientific evidence for physiological benefits of increased fiber intake, regulatory agencies such as the US [[Food and Drug Administration]] (FDA) have given approvals to food products making health claims for fiber.
In clinical trials to date, these fiber sources were shown to significantly reduce blood cholesterol levels -- thus are important to general cardiovascular health<ref>[http://www.cfsan.fda.gov/~lrd/cf101-77.html Electronic Code of Federal Regulations:<!-- Bot generated title -->]</ref> -- and to lower risk of onset for some types of cancer.<ref>[http://www.cfsan.fda.gov/~lrd/cf101-76.html Electronic Code of Federal Regulations:<!-- Bot generated title -->]</ref>
Soluble (fermentable) fiber sources gaining FDA approval are
* [[Psyllium]] seed husk (7 grams per day)
* [[Beta-glucan]] from [[oat bran]], whole [[oat]]s, oatrim or rolled oats (3 grams per day)
* Beta-glucan from whole grain or dry-milled [[barley]] (3 grams per day)
Other examples of fermentable fiber sources (from plant foods or biotechnology) used in functional foods and supplements include [[inulin]], [[fructans]], [[xanthan gum]], [[cellulose]], [[guar gum]], fructooligosaccharides (FOS) and oligo- or polysaccharides.
Consistent intake of fermentable fiber through foods like berries and other fresh [[fruit]], [[vegetable]]s, [[whole grain]]s, seeds and nuts is now known to reduce risk of some of the world’s most prevalent diseases — [[obesity]], [[diabetes]], high blood [[cholesterol]], [[cardiovascular disease]], and numerous [[gastrointestinal]] disorders. In this last category are [[constipation]], [[Irritable bowel syndrome|inflammatory bowel disease]], [[ulcerative colitis]], hemorrhoids, [[Crohn’s disease]], [[diverticulitis]], and [[colon cancer]]--all disorders of the intestinal tract where fermentable fiber can provide healthful benefits.
Insufficient fiber in the diet can complicate [[defecation]].<ref name="WebMDConst">[http://www.webmd.com/content/article/90/100651.htm Constipation<!-- Bot generated title -->]</ref> Low-fiber feces are dehydrated and hardened, making them difficult to evacuate -- defining [[constipation]]<ref name="WebMDConst" /> and possibly leading to development of [[hemorrhoid]]s<ref name="WebMDConst" /> or [[anal fissure]]s.
Although many researchers believe that dietary fiber intake reduces risk of colon cancer, one study conducted by researchers at the [[Harvard School of Medicine]] of over 88,000 women did not show a statistically significant relationship between higher fiber consumption and lower rates of colorectal cancer or adenomas.<ref>Fuchs, CS, et al. "Dietary fiber and the risk of colorectal cancer and adenoma in women." ''New England Journal of Medicine'', 21 Jan 1999:223-4.</ref>
===Summary of definition and potential health benefits===
{{Globalizecountry|United Kingdom}}
In June 2007, the [[British Nutrition Foundation]] issued a statement to define dietary fiber more concisely and list the potential health benefits established to date:<ref>[http://www.nutraingredients.com/news/ng.asp?n=77554&m=1NIE621&c=zondoewvtjilvpr British Nutrition Foundation defines 'fibre'<!-- Bot generated title -->]</ref><ref>[http://www.nutrition.org.uk/home.asp?siteId=43§ionId=1495&subSectionId=1479&parentSection=304&which=4#2003 British Nutrition Foundation<!-- Bot generated title -->]</ref>
<blockquote>‘Dietary fiber’ has been used as a collective term for a complex mixture of substances with different chemical and physical properties which exert different types of physiological effects.
The use of certain analytical methods to quantify ‘dietary fiber’ by nature of its indigestibility results in many other indigestible components being isolated along with the [[carbohydrate]] components of dietary fiber. These components include [[resistant starch]]es and [[oligosaccharides]] along with other substances that exist within the plant cell structure and contribute to the material that passes through the [[digestive tract]]. Such components are likely to have physiological effects.
Yet, some differentiation has to be made between these indigestible plant components and other partially digested material, such as [[protein]], that appears in the large [[bowel]]. Thus, it is better to classify fiber as a group of compounds with different physiological characteristics, rather than to be constrained by defining it chemically.
Diets naturally high in fiber can be considered to bring about five main physiological consequences:
# improvements in [[gastrointestinal]] health
# improvements in [[glucose tolerance]] and the [[insulin]] response
# reduction of [[hyperlipidemia]], [[hypertension]] and other [[coronary heart disease]] risk factors
# reduction in the risk of developing some [[cancers]]
# increased [[satiety]] and hence some degree of weight management
Therefore, it is not appropriate to state that fiber has a single all encompassing physiological property as these effects are dependent on the type of fiber in the diet. The beneficial effects of high fiber diets are the summation of the effects of the different types of fiber present in the diet and also other components of such diets.
Defining fiber physiologically allows recognition of indigestible carbohydrates with structures and physiological properties similar to those of naturally occurring dietary fibers.<ref>[http://www.nutrition.org.uk/home.asp?siteId=43§ionId=1495&subSectionId=1479&parentSection=304&which=4#2003 British Nutrition Foundation<!-- Bot generated title -->]</ref></blockquote>
==Guidelines on fiber intake==
The [[American Dietetic Association]] (ADA) recommends a minimum of 20-35 g/day for a healthy adult depending on calorie intake (e.g., a 2000 cal/8400 kJ diet should include 25 g of fiber per day). The ADA's recommendation for children is that intake should equal age in years plus 5 g/day (e.g., a 4 year old should consume 9 g/day). No guidelines have yet been established for the elderly or very ill. Patients with current [[constipation]], [[vomiting]], and [[abdominal pain]] should see a physician. Certain bulking agents are not commonly recommended with the prescription of [[opioid]]s because the slow transit time mixed with larger stools may lead to severe constipation, pain, or obstruction.
The [[British Nutrition Foundation]] has recommended a minimum fiber intake of 12-24 g/day for healthy adults.<ref>[http://www.nutrition.org.uk/home.asp?siteId=43§ionId=414&subSectionId=320&parentSection=299&which=1#1008 British Nutrition Foundation<!-- Bot generated title -->]</ref>
== Sources of fiber ==
Current recommendations from the [[United States National Academy of Sciences]], [[Institute of Medicine]], suggest that adults should consume 20-35 grams of dietary fiber per day, but the average American's daily intake of dietary fiber is only 12-18 grams.<ref>[http://www.hsph.harvard.edu/nutritionsource/fiber.html Fiber: Nutrition Source, Harvard School of Public Health<!-- Bot generated title -->]</ref><ref name="OregonState">[http://lpi.oregonstate.edu/infocenter/phytochemicals/fiber/ Linus Pauling Institute at Oregon State University<!-- Bot generated title -->]</ref> The [[American Dietetic Association]] recommends consuming a variety of fiber-rich foods.
'''Soluble fiber''' is found in varying quantities in all plant foods, including:
* [[legume]]s ([[pea]]s, [[soybean]]s, and other [[bean]]s)
* [[oat]]s, [[rye]], [[chia]], and [[barley]]
* some [[fruit]]s and fruit [[juice]]s (particularly [[prune]] juice, [[plum]]s and [[berry|berries]])
* certain [[vegetable]]s such as [[broccoli]], [[carrot]]s and [[Jerusalem artichokes]]
* [[root vegetable]]s such as [[potato]]es, [[sweet potato]]es, and [[onions]] (skins of these vegetables are sources of insoluble fiber)
* [[psyllium]] seed husk (a [[mucilage]] soluble fiber).
Legumes also typically contain shorter-chain carbohydrates indigestible by the human digestive tract but which may be metabolized by bacterial [[Fermentation (biochemistry)|fermentation]] in the large intestine (colon), yielding short-chain [[fatty acids]] and gases ([[flatulence]]).
Sources of '''insoluble fiber''' include:
* [[whole grain]] foods
* [[bran]]
* [[nut (fruit)|nut]]s and [[seeds]]
* vegetables such as [[green bean]]s, [[cauliflower]], [[zucchini]] (courgette), and [[celery]]
* the skins of some fruits, including [[tomato]]es
The five most fiber-rich plant foods, according to the Micronutrient Center of the [[Linus Pauling Institute]], are [[legumes]] (15-19 grams of fiber per US cup serving, including several types of [[beans]], [[lentils]] and [[peas]]), [[wheat bran]] (17 grams per cup), [[prunes]] (12 grams), [[Asian pear]] (10 grams each, 3.6% by weight), and [[quinoa]] (9 grams).<ref name="OregonState" />
Remarkable among plant foods, the Amazonian palmberry, [[açaí]] (''Euterpe oleracea'' Mart.), has been analyzed by two research groups reporting its content of dietary fiber is 25-44% of total mass in ''freeze-dried powder.''<ref>[http://thesuperberry.com/constituents.htm The Super Berry Acai - Constituents<!-- Bot generated title -->]</ref><ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17061839&query_hl=5&itool=pubmed_docsum Phytochemical and nutrient composition of the free...[J Agric Food Chem. 2006] - PubMed Result<!-- Bot generated title -->]</ref><ref>[http://www.npicenter.com/anm/templates/newsATemp.aspx?articleid=17363&zoneid=201 Açaí - Potent Antioxidant Superfruit :: News :: Natural and Nutritional Products Industry Center<!-- Bot generated title -->]</ref>
[[Rubus]] fruits such as [[raspberry]] (8 grams of fiber per serving) and [[blackberry]] (7.4 grams of fiber per serving) are exceptional sources of fiber.<ref>{{cite web | title = In-depth nutrient analysis| publisher = World's Healthiest Foods | url = http://whfoods.com/genpage.php?tname=nutrientprofile&dbid=23 }}</ref>
==FDA-approved health claims==
The [[FDA]] allows producers of foods containing 1.7 g per serving of psyllium husk soluble fiber or 0.75 g of [[oat]] or [[barley]] soluble fiber as [[beta-glucans]] to claim that reduced risk of [[heart disease]] can result from their regular consumption.<ref name="FDAc">[http://www.cfsan.fda.gov/~dms/2lg-xc.html FDA/CFSAN A Food Labeling Guide: Appendix C Health Claims, April 2008]</ref>
The FDA statement template for making this claim is: ''Soluble fiber from foods such as [name of soluble fiber source, and, if desired, name of food product], as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of food product] supplies __ grams of the [necessary daily dietary intake for the benefit] soluble fiber from [name of soluble fiber source] necessary per day to have this effect.''.<ref name="FDAc"/>
Eligible sources of soluble fiber providing beta-glucan include:
# Oat bran
# Rolled oats
# Whole oat flour
# Oatrim
# Whole grain barley and dry milled barley
# Soluble fiber from psyllium husk with purity of no less than 95%
The allowed label may state that diets low in saturated fat and cholesterol and that include soluble fiber from certain of the above foods “may” or “might” reduce the risk of heart disease.
As discussed in FDA regulation 21 CFR 101.81, the daily dietary intake levels of soluble fiber from sources listed above associated with reduced risk of [[coronary heart disease]] are:
* 3 g or more per day of beta-glucan soluble fiber from either whole oats or barley, or a combination of whole oats and barley
*7 g or more per day of soluble fiber from psyllium seed husk.<ref>Soluble Fiber from Certain Foods and Risk of Coronary Heart Disease, U.S. Government Printing Office, Electronic Code of Federal Regulations, Title 21: Food and Drugs, part 101: Food Labeling, Subpart E, Specific Requirements for Health Claims, 101.81[http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=77ed7da9463357d9a09892213e5c74db&rgn=div8&view=text&node=21:2.0.1.1.2.5.1.12&idno=21]</ref>
Soluble fiber from consuming grains is included in other allowed health claims for lowering risk of some types of cancer and heart disease by consuming fruit and vegetables (21 CFR 101.76, 101.77 and 101.78).<ref name="FDAc"/>
==Fiber supplements==
There are many types of soluble fiber supplements available to consumers for nutritional purposes, treatment of various [[gastrointestinal]] disorders, and for such possible health benefits as lowering [[cholesterol]] levels, reducing risk of [[colon cancer]], and losing weight.
Soluble fiber supplements may be beneficial for alleviating symptoms of [[irritable bowel syndrome]], such as [[diarrhea]] and/or [[constipation]] and abdominal discomfort.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=2553606&query_hl=19&itool=pubmed_docsum Nutritional therapy of irritable bowel syndrome. [Gastroenterol Clin North Am. 1989] - PubMed Result<!-- Bot generated title -->]</ref> [[Prebiotic (nutrition)|Prebiotic]] soluble fiber products, like those containing [[inulin]] or [[oligosaccharides]], may contribute to relief from [[inflammatory bowel disease]],<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17009391&query_hl=7&itool=pubmed_docsum Probiotics and prebiotics in chronic inflammatory ...[World J Gastroenterol. 2006] - PubMed Result<!-- Bot generated title -->]</ref> as in [[Crohn's disease]],<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15877897&query_hl=1&itool=pubmed_docsum Inulin and oligofructose: impact on intestinal dis...[Br J Nutr. 2005] - PubMed Result<!-- Bot generated title -->]</ref> [[ulcerative colitis]],<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15822041&query_hl=9&itool=pubmed_docsum An oral supplement enriched with fish oil, soluble...[Clin Gastroenterol Hepatol. 2005] - PubMed Result<!-- Bot generated title -->]</ref>
<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=14512034&query_hl=1&itool=pubmed_docsum Intestinal anti-inflammatory activity of dietary f...[Clin Nutr. 2003] - PubMed Result<!-- Bot generated title -->]</ref> and ''[[Clostridium difficile]]'',<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=9191992&query_hl=11&itool=pubmed_docsum Dynamics of Clostridium difficile infection. Contr...[Adv Exp Med Biol. 1997] - PubMed Result<!-- Bot generated title -->]</ref> due in part to the short-chain [[fatty acids]] produced with subsequent [[anti-inflammatory]] actions upon the bowel.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=12212362&query_hl=1&itool=pubmed_docsum Short-chain fatty acids: bacterial mediators of a ...[Wien Klin Wochenschr. 2002] - PubMed Result<!-- Bot generated title -->]</ref>
<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=12875900&query_hl=1&itool=pubmed_docsum Differential effects of short-chain fatty acids on...[Life Sci. 2003] - PubMed Result<!-- Bot generated title -->]</ref> Fiber supplements may be effective in an overall dietary plan for managing [[irritable bowel syndrome]] by modification of food choices.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17206644&query_hl=15&itool=pubmed_docsum Treatment of irritable bowel syndrome in outpatien...[Inflamm Bowel Dis. 2007] - PubMed Result<!-- Bot generated title -->]</ref>
===Psyllium husk===
[[Psyllium seed husks|Psyllium seed husk]] may reduce the risk of heart disease by lowering cholesterol levels, and is known to help alleviate the symptoms of [[irritable bowel syndrome]], though it often causes uncomfortable bloating. Psyllium husk may be used as a bulk-forming [[laxative]].
In clinical studies approved by the FDA, the cholesterol-lowering benefit of soluble fiber from psyllium, when taken as directed and combined with a low-fat, low-cholesterol diet, was 4 to 6 percent for total blood cholesterol and 4 to 8 percent for LDL (bad) cholesterol vs. a low-fat diet alone.<ref>[http://www.cfsan.fda.gov/~lrd/fr980409.html Federal Register 63 FR 17327, April 9, 1998 - Food Labeling: Health Claims; Soluble Fiber From Certain Foods and Coronary Heart Disease; Correction<!-- Bot generated title -->]</ref>
===Inulins===
Chemically defined as [[oligosaccharide]]s occurring naturally in most plants, [[inulin]]s have nutritional value as [[carbohydrates]], or more specifically as [[fructan]]s, a [[polymer]] of the natural plant sugar, [[fructose]]. Inulin is typically extracted by manufacturers from enriched plant sources such as [[chicory]] roots or [[Jerusalem artichoke]]s for use in prepared foods.<ref>[http://www.ncbi.nlm.nih.gov/pubmed/12571376 Kaur N, Gupta AK. Applications of inulin and oligofructose in health and nutrition. J Biosci. 2002 Dec;27(7):703-14.]</ref> Subtly sweet, it can be used to replace sugar, fat, and flour, is often used to improve the flow and mixing qualities of powdered [[nutritional supplements]], and has significant potential health value as a [[prebiotic]] fermentable fiber.<ref>[http://www.ncbi.nlm.nih.gov/pubmed/17951492 Roberfroid MB. Inulin-type fructans: functional food ingredients. J Nutr. 2007 Nov;137(11 Suppl):2493S-2502S.]</ref>
Inulin is advantageous because it contains 25-30% the [[food energy]] of sugar or other carbohydrates and 10-15% the food energy of fat. As a [[prebiotic]] fermentable fiber, its metabolism by [[gut flora]] yields short-chain fatty acids (discussed above) which increase absorption of [[calcium]],<ref>{{cite journal | author = Abrams S, Griffin I, Hawthorne K, Liang L, Gunn S, Darlington G, Ellis K | title = A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents. | journal = Am J Clin Nutr | volume = 82 | issue = 2 | pages = 471–6 | year = 2005 | pmid = 16087995}}</ref> [[magnesium]],<ref>{{cite journal | author = Coudray C, Demigné C, Rayssiguier Y | title = Effects of dietary fibers on magnesium absorption in animals and humans. | journal = J Nutr | volume = 133 | issue = 1 | pages = 1–4 | year = 2003 | pmid = 12514257}}</ref> and [[iron]],<ref>{{cite journal | author = Tako E, Glahn RP, Welch RM, Lei X, Yasuda K, Miller DD. | title = Dietary inulin affects the expression of intestinal enterocyte iron transporters, receptors and storage protein and alters the microbiota in the pig intestine. | journal = Br J Nutr. | issue = Sep | pages = 1–9 | year = 2007 | pmid = 17868492}}</ref> resulting from upregulation of mineral-transporting [[gene]]s and their [[membrane transport proteins]] within the colon wall. Among other potential beneficial effects noted above, inulin promotes an increase in the mass and health of intestinal ''[[Lactobacillus]]'' and ''[[Bifidobacterium]]'' populations.
===Vegetable gums===
[[Natural gum|Vegetable gum]] fiber supplements are relatively new to the market. Often sold as a powder, vegetable gum fibers dissolve easily with no aftertaste. They are effective for the treatment of [[irritable bowel syndrome]] (Parisi, 2002).{{Verify source|date=July 2007}} Examples of vegetable gum fibers are [[guar gum]] (example brand Benefiber reformulated to wheat [[dextrin]] in 2006)<ref>[http://www.benefiber.com/fiberHealth/index.shtml?faqs#question1 Benefiber<!-- Bot generated title -->]</ref> and [[gum arabic|acacia gum]].
==Misconceptions==
Fiber does not bind to minerals and vitamins and therefore does not restrict their absorption, but rather evidence exists that fermentable fiber sources improve absorption of minerals, especially calcium.<ref>[http://www.ncbi.nlm.nih.gov/pubmed/10395614 Nondigestible carbohydrates and mineral bioavailab...[J Nutr. 1999] - PubMed Result<!-- Bot generated title -->]</ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/16126464 Mechanisms underlying the effects of inulin-type f...[Bone. 2005] - PubMed Result<!-- Bot generated title -->]</ref> Some plant foods can reduce the absorption of minerals and vitamins like [[calcium]], [[zinc]], [[vitamin C]] and [[magnesium]], but this is caused by the presence of [[phytate]] (which is also thought to have important health benefits), not by fiber.<ref>[http://lpi.oregonstate.edu/infocenter/phytochemicals/fiber/ Linus Pauling Institute at Oregon State University<!-- Bot generated title -->]</ref>
==See also==
*[[Prebiotic (nutrition)|Prebiotic]] — indigestible matter which encourages growth of [[gut flora]]
*[[Low residue diet]]
*[[Resistant starch]]
*[[Methylcellulose]]
==Notes==
{{reflist|2}}
==References==
* Fiber, Harvard School of Public Health, http://www.hsph.harvard.edu/nutritionsource/fiber.html
* Fiber Health Claims That Meet Significant Scientific Agreement, US Food and Drug Administration, http://www.cfsan.fda.gov/~dms/lab-ssa.html
* Fiber 101: Soluble fiber vs. insoluble fiber, HealthCastle.com - http://www.healthcastle.com/fiber-solubleinsoluble.shtml
* Higgins JA. Resistant starch: metabolic effects and potential health benefits. ''Journal of AOAC International'' 87:761-767, 2004.
* Tungland BC, Meyer D. Nondigestible oligo- and polysaccharides (dietary fiber): their physiology and role in human health and food. ''Comprehensive Reviews in Food Science and Food Safety'' 1:73-92, 2002.
* Parisi, G.C., Zill, M. et al. High-fiber diet supplementation in patients with irritable bowel syndrome (IBS): A multicenter, randomized, [[open trial (medical)|open trial]] comparison between wheat bran diet and partially hydrolyzed guar gum. ''Digestive diseases and sciences'' Volume 47 number 8:1697-1704, 2002.
* Marlett JA. Dietary fiber and cardiovascular disease. In: Cho SS, Dreher ML, eds. Handbook of Dietary Fiber. New York: Marcel Dekker, Inc; 2001:17-30.
* US Food and Drug Administration. Health Claims: Soluble fiber from certain foods and risk of heart diseases. Code of Federal Regulations. 2001;21:101.81.
* Eastwood MA, Brydon WG. Tadesse K. Effect of fiber on colon function. In: Spiller GA, Kay RM, eds. Medical Aspects of Dietary Fiber. New York, NY: Plenum Press; 1980:1-26.
* Prynne CJ, Southgate DAT. The effects of a supplement of dietary fibre on faecal excretion by human subjects. Br J Nutr. 1979;41:495-503.
==External links==
* [http://www.health.gov/dietaryguidelines/dga2005/document/html/appendixB.htm Food Sources of Dietary Fiber, Appendix B-8, Dietary Guidelines for Americans published jointly in 2005 by the US Department of Health and Human Services and the Department of Agriculture]
* [http://www.webmd.com/content/article/90/100599.htm Anatomy and Function of the Human Digestive System]
{{Dietary supplement}}
[[Category:Nutrition]]
[[Category:Dietary supplements]]
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[[cs:Vláknina]]
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