- Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:
- soluble (prebiotic, viscous) fiber that is readily fermented in the colon into gases and physiologically active byproducts, and
- insoluble fiber that is metabolically inert, absorbing water as it moves through the digestive system, easing defecation.
It acts by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed. Soluble fiber absorbs water to become a gelatinous, viscous substance and is fermented by bacteria in the digestive tract. Insoluble fiber has bulking action and is not fermented. Lignin, a major dietary insoluble fiber source, may alter the fate and metabolism of soluble fibers.
Chemically, dietary fiber consists of non-starch polysaccharides such as arabinoxylans, cellulose, and many other plant components such as resistant dextrins, inulin, lignin, waxes, chitins, pectins, beta-glucans, and oligosaccharides. A novel position has been adopted by the US Department of Agriculture to include functional fibers as isolated fiber sources that may be included in the diet. The term "fiber" is something of a misnomer, since many types of so-called dietary fiber are not actually fibrous.
Food sources of dietary fiber are often divided according to whether they provide (predominantly) soluble or insoluble fiber. Plant foods contain both types of fiber in varying degrees, according to the plant's characteristics.
Advantages of consuming fiber are the production of healthful compounds during the fermentation of soluble fiber, and insoluble fiber's ability (via its passive hygroscopic properties) to increase bulk, soften stool, and shorten transit time through the intestinal tract.
Disadvantages of a diet high in fiber is the potential for significant intestinal gas production and bloating. Constipation can occur if insufficient fluid is consumed with a high-fiber diet.
History of definition
Originally, fiber was defined to be the components of plants that resist human digestive enzymes, a definition that includes lignin and polysaccharides. The definition was later changed to also include resistant starches, along with inulin and other oligosaccharides.
Sources of fiber
Dietary fiber is found in plants. While all plants contain some fiber, plants with high fiber concentrations are generally the most practical source.
Fiber-rich plants can be eaten directly. Or, alternatively, they can be used to make supplements and fiber-rich processed foods.
The American Dietetic Association (ADA) recommends consuming a variety of fiber-rich foods.
Plant sources of fiber
Some plants contain significant amounts of soluble and insoluble fiber. For example plums (or prunes) 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.
Soluble fiber is found in varying quantities in all plant foods, including:
- legumes (peas, soybeans, lupins and other beans)
- oats, rye, chia, and barley
- some fruits and fruit juices (including prune juice, plums, berries, bananas, and the insides of apples and pears)
- certain vegetables such as broccoli, carrots, and Jerusalem artichokes
- root tubers and root vegetables such as sweet potatoes and onions (skins of these are sources of insoluble fiber)
- psyllium seed husk (a mucilage soluble fiber).
Sources of insoluble fiber include:
- whole grain foods
- wheat and corn bran
- nuts and seeds
- potato skins
- flax and hemp seed
- vegetables such as green beans, cauliflower, zucchini (courgette), celery, and nopal
- some fruits including avocado, and bananas
- the skins of some fruits, including kiwifruit and tomatoes
These are a few example forms of fiber that have been sold as supplements or food additives. These may be marketed 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. Prebiotic soluble fiber products, like those containing inulin or oligosaccharides, may contribute to relief from inflammatory bowel disease, as in Crohn's disease, ulcerative colitis, and Clostridium difficile, due in part to the short-chain fatty acids produced with subsequent anti-inflammatory actions upon the bowel. fiber supplements may be effective in an overall dietary plan for managing irritable bowel syndrome by modification of food choices.
Chemically defined as oligosaccharides occurring naturally in most plants, inulins have nutritional value as carbohydrates, or more specifically as fructans, a polymer of the natural plant sugar, fructose. Inulin is typically extracted by manufacturers from enriched plant sources such as chicory roots or Jerusalem artichokes for use in prepared foods. 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.
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, magnesium, and iron, resulting from upregulation of mineral-transporting genes 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 gum fiber supplements are relatively new to the market. Often sold as a powder, vegetable gum fibers dissolve easily with no aftertaste. In preliminary clinical trials, they have proven effective for the treatment of irritable bowel syndrome. Examples of vegetable gum fibers are guar gum and acacia Senegal gum.
The main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed. Soluble fiber binds to bile acids in the small intestine, making them less likely to enter the body; this in turn lowers cholesterol levels in the blood. Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.
Not yet formally proposed as an essential macronutrient, dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake.
Effects of fiber intake
Research has shown that fiber may benefit health in several different ways. Lignin and probably related materials that are resistant to enzymatic degradation, diminish the nutritional value of foods.
Color coding of table entries:
- Applies to both soluble and insoluble fiber
- Applies to soluble fiber only
- Applies to insoluble fiber only
Dietary fiber functions and benefits
Functions Benefits Increases food volume without increasing caloric content, providing satiety May reduce appetite Attracts water and forms a viscous gel during digestion, slowing the emptying of the stomach and intestinal transit, shielding carbohydrates from enzymes, and delaying absorption of glucose Lowers variance in blood sugar levels Lowers total and LDL cholesterol Reduces risk of cardiovascular disease Regulates blood sugar May reduce glucose and insulin levels in diabetic patients and may lower risk of diabetes Speeds the passage of foods through the digestive system Facilitates regular defecation Adds bulk to the stool Alleviates constipation Balances intestinal pH and stimulates intestinal fermentation production of short-chain fatty acids May reduce risk of colorectal cancer
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. 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.
Guidelines on fiber intake
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.
The 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 25g 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 opioids because the slow transit time mixed with larger stools may lead to severe constipation, pain, or obstruction.
Fiber recommendations in North America
On average, North Americans consume less than 50% of the dietary fiber levels recommended 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 levels seen in many developed countries.
Recognizing the growing scientific evidence for physiological benefits of increased fiber intake, regulatory agencies such as the Food and Drug Administration (FDA) of the United States 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, an important factor for general cardiovascular health, and to lower risk of onset for some types of cancer.
Soluble (fermentable) fiber sources gaining FDA approval are:
- Psyllium seed husk (7 grams per day)
- Beta-glucan from oat bran, whole oats, 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, resistant dextrins, 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, vegetables, whole grains, 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, 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. Low-fiber feces are dehydrated and hardened, making them difficult to evacuate—defining constipation and possibly leading to development of hemorrhoids or anal fissures.
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.
Fiber recommendations in the UK
‘Dietary fibre’ 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 starches 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 several main physiological consequences:
- helps prevent constipation
- reduces the risk of colon cancer
- 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
Fiber and calories
Fiber, a type of carbohydrate, contributes less energy (measured in Calories or kilojoules) than sugars and starches because it cannot be fully absorbed by the body. Sugars and starches provide 4 Calories per gram, and the human body has specific enzymes to break them down into glucose, fructose, and galactose, which can then be absorbed by the body. The human body lacks enzymes to break down fiber. Insoluble fiber does not change inside the body, so the body cannot absorb it and nutritionists say that it contributes 0 Calories per gram. Soluble fiber is partially fermented, with the degree of fermentability varying with the type of fiber, and contributes some energy when broken down and absorbed by the body. Dietitians have not reached a consensus on how much energy is actually absorbed, but some approximate around 2 Calories (8.5 kilojoules) per gram of soluble fiber. Regardless of the type of fiber, the body absorbs fewer than 4 Calories (16.7 kilojoules) per gram of fiber, which can create inconsistencies for actual product nutrition labels. In some countries, fiber is not listed on nutrition labels, and is considered 0 Calories/gram when the food's total Calories are computed. In other countries all fiber must be listed, and is considered 4 Calories per gram when the food's total Calories are computed (because chemically fiber is a type of carbohydrate and other carbohydrates contribute 4 Calories per gram). In the US, soluble fiber must be counted as 4 Calories per gram, but insoluble fiber may be (and usually is) treated as 0 Calories per gram and not mentioned on the label.
Soluble fiber fermentation
The American Association of Cereal Chemists has 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.” In this definition:
- 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.
- complex carbohydrates, such as long-chained sugars also called starch, oligosaccharides, or polysaccharides, are 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 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, acetic (ethanoic), propionic, and valeric acids—that scientific evidence is revealing to have significant health properties.
As an example of fermentation, shorter-chain carbohydrates (a type of fiber found in legumes) cannot be digested, but are changed via fermentation in the colon into short-chain fatty acids and gases (which are typically expelled as flatulence).
According to a 2002 journal article, fibers compounds with partial or low fermentability include:
- cellulose, a polysaccharide
- hemicellulose, a polysaccharide
- lignans, a group of phytoestrogens
- plant waxes
- resistant starches
fiber compounds with high fermentability include:
- beta-glucans, a group of polysaccharides
- pectins, a group of heteropolysaccharides
- natural gums, a group of polysaccharides
- inulins, a group of polysaccharides
- oligosaccharides, a group of short-chained or simple sugars
- resistant dextrins
Short-chain fatty acids
- stabilize blood glucose levels by acting on pancreatic insulin release and liver control of glycogen breakdown
- stimulate gene expression of glucose transporters in the intestinal mucosa, regulating glucose absorption
- provide nourishment of colonocytes, particularly by the SCFA butyrate
- suppress cholesterol synthesis by the liver and reduce blood levels of LDL cholesterol and triglycerides responsible for atherosclerosis
- lower colonic pH (i.e., raises the acidity level in the colon) which protects the lining from formation of colonic polyps and increases absorption of dietary minerals
- stimulate production of T helper cells, antibodies, leukocytes, cytokines, and lymph mechanisms having crucial roles in immune protection
- improve barrier properties of the colonic mucosal layer, inhibiting inflammatory and adhesion irritants, contributing to immune functions
The major SCFAs in humans are butyrate, propionate, and acetate, where butyrate is the major energy source for colonocytes, propionate is destined for uptake by the liver, and acetate enters the peripheral circulation to be metabolized by peripheral tissues.
FDA-approved health claims
The FDA allows producers of foods containing 1.7g per serving of psyllium husk soluble fiber or 0.75g of oat or barley soluble fiber as beta-glucans to claim that reduced risk of heart disease can result from their regular consumption.
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.
Eligible sources of soluble fiber providing beta-glucan include:
- Oat bran
- Rolled oats
- Whole oat flour
- 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:
- 3g or more per day of beta-glucan soluble fiber from either whole oats or barley, or a combination of whole oats and barley
- 7g or more per day of soluble fiber from psyllium seed husk.
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).
A study of 388,000 adults ages 50 to 71 for nine years found that the highest consumers of fiber were 22% less likely to die over this period. In addition to lowering the risk of death from heart disease, adequate consumption of fiber-containing foods, especially grains, also appeared to reduce the incidence of infectious and respiratory illnesses, and, particularly among males, lowered the risk of cancer-related death.
- High residue diet
- Low residue diet
- Prebiotic—indigestible matter which encourages growth of gut flora
- Resistant starch
- ^ a b c d e f "Dietary Reference Intakes for Energy, Carbohydrate, fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (2005), Chapter 7: Dietary, Functional and Total fiber.". US Department of Agriculture, National Agricultural Library and National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. http://www.nal.usda.gov/fnic/DRI//DRI_Energy/339-421.pdf.
- ^ a b c Eastwood M, Kritchevsky D (2005). "Dietary fiber: how did we get where we are?". Annu Rev Nutr 25: 1–8. doi:10.1146/annurev.nutr.25.121304.131658. PMID 16011456.
- ^ a b c Anderson JW, Baird P, Davis RH et al. (2009). "Health benefits of dietary fiber". Nutr Rev 67 (4): 188–205. doi:10.1111/j.1753-4887.2009.00189.x. PMID 19335713.
- ^ Stacewicz-Sapuntzakis M, Bowen PE, Hussain EA, Damayanti-Wood BI, Farnsworth NR (May 2001). "Chemical composition and potential health effects of prunes: a functional food?". Crit Rev Food Sci Nutr. 41 (4): 251–86. doi:10.1080/20014091091814. PMID 11401245.
- ^ Alvarado A, Pacheco-Delahaye E, Hevia P (2001). "Value of a tomato byproduct as a source of dietary fiber in rats". Plant Foods Hum Nutr. 56 (4): 335–48. doi:10.1023/A:1011855316778. PMID 11678439. http://www.kluweronline.com/art.pdf?issn=0921-9668&volume=56&page=335.
- ^ Friedman G (September 1989). "Nutritional therapy of irritable bowel syndrome". Gastroenterol Clin North Am. 18 (3): 513–24. PMID 2553606.
- ^ Ewaschuk JB, Dieleman LA (October 2006). "Probiotics and prebiotics in chronic inflammatory bowel diseases". World J Gastroenterol. 12 (37): 5941–50. PMID 17009391. http://www.wjgnet.com/1007-9327/12/5941.asp.
- ^ Guarner F (April 2005). "Inulin and oligofructose: impact on intestinal diseases and disorders". Br J Nutr. 93 Suppl 1: S61–5. doi:10.1079/BJN20041345. PMID 15877897. http://journals.cambridge.org/abstract_S0007114505000826.
- ^ Seidner DL, Lashner BA, Brzezinski A, et al. (April 2005). "An oral supplement enriched with fish oil, soluble fiber, and antioxidants for corticosteroid sparing in ulcerative colitis: a randomized, controlled trial". Clin Gastroenterol Hepatol. 3 (4): 358–69. doi:10.1016/S1542-3565(04)00672-X. PMID 15822041.
- ^ Rodríguez-Cabezas ME, Gálvez J, Camuesco D, et al. (October 2003). "Intestinal anti-inflammatory activity of dietary fiber (Plantago ovata seeds) in HLA-B27 transgenic rats". Clin Nutr. 22 (5): 463–71. doi:10.1016/S0261-5614(03)00045-1. PMID 14512034. http://linkinghub.elsevier.com/retrieve/pii/S0261561403000451.
- ^ Ward PB, Young GP (1997). "Dynamics of Clostridium difficile infection. Control using diet". Adv Exp Med Biol. 412: 63–75. PMID 9191992.
- ^ Säemann MD, Böhmig GA, Zlabinger GJ (May 2002). "Short-chain fatty acids: bacterial mediators of a balanced host-microbial relationship in the human gut". Wien Klin Wochenschr. 114 (8–9): 289–300. PMID 12212362.
- ^ Cavaglieri CR, Nishiyama A, Fernandes LC, Curi R, Miles EA, Calder PC (August 2003). "Differential effects of short-chain fatty acids on proliferation and production of pro- and anti-inflammatory cytokines by cultured lymphocytes". Life Sciences 73 (13): 1683–90. doi:10.1016/S0024-3205(03)00490-9. PMID 12875900. http://linkinghub.elsevier.com/retrieve/pii/S0024320503004909.
- ^ MacDermott RP (January 2007). "Treatment of irritable bowel syndrome in outpatients with inflammatory bowel disease using a food and beverage intolerance, food and beverage avoidance diet". Inflamm Bowel Dis. 13 (1): 91–6. doi:10.1002/ibd.20048. PMID 17206644.
- ^ Kaur N, Gupta AK (December 2002). "Applications of inulin and oligofructose in health and nutrition" (PDF). J Biosci. 27 (7): 703–14. doi:10.1007/BF02708379. PMID 12571376. http://www.ias.ac.in/jbiosci/dec2002/703.pdf.
- ^ Roberfroid MB (November 1, 2007). "Inulin-type fructans: functional food ingredients". J Nutr. 137 (11 Suppl): 2493S–2502S. PMID 17951492. http://jn.nutrition.org/cgi/pmidlookup?view=long&pmid=17951492.
- ^ Abrams S, Griffin I, Hawthorne K, Liang L, Gunn S, Darlington G, Ellis K (2005). "A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents". Am J Clin Nutr 82 (2): 471–6. PMID 16087995.
- ^ Coudray C, Demigné C, Rayssiguier Y (2003). "Effects of dietary fibers on magnesium absorption in animals and humans". J Nutr 133 (1): 1–4. PMID 12514257.
- ^ Tako E, Glahn RP, Welch RM, Lei X, Yasuda K, Miller DD. (2007). "Dietary inulin affects the expression of intestinal enterocyte iron transporters, receptors and storage protein and alters the microbiota in the pig intestine". Br J Nutr. 99 (Sep): 1–9. doi:10.1017/S0007114507825128. PMID 17868492.
- ^ Parisi GC, Zilli M, Miani MP, Carrara M, Bottona E, Verdianelli G, Battaglia G, Desideri S, Faedo A, Marzolino C, Tonon A, Ermani M, Leandro G. (2002). "High-fiber diet supplementation in patients with irritable bowel syndrome (IBS): a multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG)". Dig Dis Sci. 47 (8): 1697–704. doi:10.1023/A:1016419906546. PMID 12184518.
- ^ Weickert MO, Pfeiffer AF (2008). "Metabolic effects of dietary fiber consumption and prevention of diabetes". J Nutr 138 (3): 439–42. PMID 18287346.
- ^ "Dietary reference values for carbohydrates and dietary fiber". European Food Safety Authority. http://www.efsa.europa.eu/EFSA/DocumentSet/nda_op_drv_carbohydrates_draft_en_released%20for%20consultation,0.pdf?ssbinary=true.
- ^ Jones PJ, Varady KA (2008). "Are functional foods redefining nutritional requirements?" (PDF). Appl Physiol Nutr Metab 33 (1): 118–23. doi:10.1139/H07-134. PMID 18347661. http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1715-5312&volume=33&issue=1&startPage=118.
- ^ Boerjan, W.; Ralph, J. and Baucher, M., "Lignin Biosynthesis", Annu. Rev. Plant Biol. 2003. 54:519–46, 2003, 54, 519–46. doi:10.1146/annurev.arplant.54.031902.134938
- ^ "MedlinePlus Medical Encyclopedia: fiber". http://www.nlm.nih.gov/medlineplus/ency/article/002470.htm. Retrieved 22 April 2009.
- ^ "University of MD Medical Center Encyclopedia entry for fiber". http://www.umm.edu/ency/article/002470all.htm. Retrieved 22 April 2009.
- ^ Gropper, Sareen S.; Jack L. Smith, James L. Groff (2008). Advanced nutrition and human metabolism (5th ed.). Cengage Learning. p. 114. ISBN 9780495116578. http://books.google.com/?id=rXSO9YLr72YC&pg=PA114&dq=soluble+fiber+viscosity+glucose#v=onepage&q=soluble%20fiber%20viscosity%20glucose&f=false.
- ^ Food and Nutrition Board, Institute of Medicine of the National Academies (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). National Academies Press. pp. 380–382. http://www.nap.edu/openbook/10490/png/380.png.
- ^ Spiller, Gene; Margo N. Woods, Sherwood L. Gorbach (27 June 2001). Influence of fiber on the ecology of the intestinal flora. CRC Press. p. 257. ISBN 9780849323874. http://books.google.com/?id=Jjdqw6n5zAQC&pg=PA257&dq=fiber+Balance+%22intestinal+pH%22. Retrieved 22 April 2009.
- ^ "Role of probiotics, prebiotics and synbiotics in chemoprevention for colorectal cancer" (PDF). World Journal of Gastroenterology. 14 (The WJG Press) (42): 6454. November 14, 2008. ISSN 1007-9327. http://www.wjgnet.com/1007-9327/14/6453.pdf. Retrieved 22 April 2009.
- ^ Greger JL (July 1999). "Nondigestible carbohydrates and mineral bioavailability". J Nutr. 129 (7 Suppl): 1434S–5S. PMID 10395614. http://jn.nutrition.org/cgi/pmidlookup?view=long&pmid=10395614.
- ^ Raschka L, Daniel H (November 2005). "Mechanisms underlying the effects of inulin-type fructans on calcium absorption in the large intestine of rats". Bone 37 (5): 728–35. doi:10.1016/j.bone.2005.05.015. PMID 16126464.
- ^ Scholz-Ahrens KE, Schrezenmeir J (Nov 2007). "Inulin and oligofructose and mineral metabolism: the evidence from animal trials". J Nutr. 137 (11 Suppl): 2513S–2523S. PMID 17951495.
- ^ a b Linus Pauling Institute at Oregon State University
- ^ fiber: Nutrition Source, Harvard School of Public Health
- ^ Dietary fiber. British Nutrition Foundation.
- ^ Lustig RH (December 2006). "The 'skinny' on childhood obesity: how our western environment starves kids' brains". Pediatr Ann. 35 (12): 898–902, 905–7. PMID 17236437.
- ^ Suter PM (2005). "Carbohydrates and dietary fiber". Handb Exp Pharmacol.. Handbook of Experimental Pharmacology 170 (170): 231–61. doi:10.1007/3-540-27661-0_8. ISBN 3-540-22569-2. PMID 16596802. http://www.springerlink.comopenurl.asp?genre=chapter&issn=0171-2004&volume=&page=231. [dead link]
- ^ Health claims: fruits, vegetables, and grain products that contain fiber, particularly soluble fiber, and risk of coronary heart disease. Electronic Code of Federal Regulations: US Government Printing Office, current as of October 20, 2008
- ^ Health claims: fiber-containing grain products, fruits, and vegetables and cancer. Electronic Code of Federal Regulations:US Government Printing Office, current as of October 20, 2008
- ^ a b c 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)
- ^ Venn BJ, Mann JI (November 2004). "Cereal grains, legumes and diabetes". Eur J Clin Nutr. 58 (11): 1443–61. doi:10.1038/sj.ejcn.1601995. PMID 15162131.
- ^ Lee YP, Puddey IB, Hodgson JM (April 2008). "Protein, fiber and blood pressure: potential benefit of legumes". Clin Exp Pharmacol Physiol. 35 (4): 473–6. doi:10.1111/j.1440-1681.2008.04899.x. PMID 18307744.
- ^ Theuwissen E, Mensink RP (May 2008). "Water-soluble dietary fibers and cardiovascular disease". Physiol Behav. 94 (2): 285–92. doi:10.1016/j.physbeh.2008.01.001. PMID 18302966.
- ^ a b c WebMD Constipation
- ^ Fuchs CS, Giovannucci EL, Colditz GA, et al. (January 1999). "Dietary fiber and the risk of colorectal cancer and adenoma in women". N Engl J Med. 340 (3): 169–76. doi:10.1056/NEJM199901213400301. PMID 9895396. http://content.nejm.org/cgi/pmidlookup?view=short&pmid=9895396&promo=ONFLNS19.
- ^ British Nutrition Foundation defines 'fibre'
- ^ a b British Nutrition Foundation
- ^ http://www.aaccnet.org/DietaryFiber/pdfs/dietfiber.pdf
- ^ a b Wong JM, de Souza R, Kendall CW, Emam A, Jenkins DJ (March 2006). "Colonic health: fermentation and short chain fatty acids". J Clin Gastroenterol. 40 (3): 235–43. doi:10.1097/00004836-200603000-00015. PMID 16633129. http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?an=00004836-200603000-00015.
- ^ Institute of Medicine (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Washington, D.C: National Academies Press. pp. 347. ISBN 0-309-08525-X.
- ^ Drozdowski LA, Dixon WT, McBurney MI, Thomson AB (2002). "Short-chain fatty acids and total parenteral nutrition affect intestinal gene expression". J Parenter Enteral Nutr. 26 (3): 145–50. doi:10.1177/0148607102026003145. PMID 12005453. http://pen.sagepub.com/cgi/pmidlookup?view=long&pmid=12005453.
- ^ Roy CC, Kien CL, Bouthillier L, Levy E (August 2006). "Short-chain fatty acids: ready for prime time?". Nutr Clin Pract. 21 (4): 351–66. doi:10.1177/0115426506021004351. PMID 16870803. http://ncp.sagepub.com/cgi/pmidlookup?view=long&pmid=16870803.
- ^ Scholz-Ahrens KE, Ade P, Marten B, et al. (March 1, 2007). "Prebiotics, probiotics, and synbiotics affect mineral absorption, bone mineral content, and bone structure". J Nutr. 137 (3 Suppl 2): 838S–46S. PMID 17311984. http://jn.nutrition.org/cgi/pmidlookup?view=long&pmid=17311984.
- ^ a b c FDA/CFSAN A Food Labeling Guide: Appendix C Health Claims, April 2008
- ^ 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 
- ^ Park Y, Subar AF, Hollenbeck A, Schatzkin A (Feb 14, 2011). "Dietary fiber intake and mortality in the NIH-AARP Diet and Health Study". Arch Intern Med 171 (12): 1061–8. doi:10.1001/archinternmed.2011.18. PMID 21321288.
- Fiber, Harvard School of Public Health
- Fiber Health Claims That Meet Significant Scientific Agreement, US Food and Drug Administration
- Higgins JA (2004). "Resistant starch: metabolic effects and potential health benefits". J AOAC Int. 87 (3): 761–8. PMID 15287677.
- 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 GC, Zilli M, Miani MP, et al. (August 2002). "High-fiber diet supplementation in patients with irritable bowel syndrome (IBS): a multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG)". Dig Dis Sci. 47 (8): 1697–704. doi:10.1023/A:1016419906546. PMID 12184518. http://www.kluweronline.com/art.pdf?issn=0163-2116&volume=47&page=1697.
- Marlett JA (2001). "Dietary fiber and cardiovascular disease". In Dreher ML, Cho SS. Handbook of dietary fiber. New York: M. Dekker. pp. 17–30. ISBN 0-8247-8960-1.
- 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 (1980). "Effect of fiber on colon function". In Kay R, Spiller GA. Medical aspects of dietary fiber. New York: Plenum Medical Book Co. pp. 1–26. ISBN 0-306-40507-5.
- Prynne CJ, Southgate DA (May 1979). "The effects of a supplement of dietary fiber on faecal excretion by human subjects". Br J Nutr. 41 (3): 495–503. doi:10.1079/BJN19790064. PMID 465439.
- 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
- Anatomy and Function of the Human Digestive System
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dietary fiber — Fiber Fi ber, Fibre Fi bre,, n. [F. fibre, L. fibra.] 1. One of the delicate, threadlike portions of which the tissues of plants and animals are in part constituted; as, the fiber of flax or of muscle. [1913 Webster] 2. Any fine, slender thread,… … The Collaborative International Dictionary of English
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Fiber — Fi ber, Fibre Fi bre,, n. [F. fibre, L. fibra.] 1. One of the delicate, threadlike portions of which the tissues of plants and animals are in part constituted; as, the fiber of flax or of muscle. [1913 Webster] 2. Any fine, slender thread, or… … The Collaborative International Dictionary of English
Fiber gun — Fiber Fi ber, Fibre Fi bre,, n. [F. fibre, L. fibra.] 1. One of the delicate, threadlike portions of which the tissues of plants and animals are in part constituted; as, the fiber of flax or of muscle. [1913 Webster] 2. Any fine, slender thread,… … The Collaborative International Dictionary of English
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