diabetes speeds the passage of foods through the digestive system, which facilitates regular defecation adds bulk to the stool, which alleviates constipation balances intestinal ph and stimulates intestinal fermentation production of short-chain fatty acids 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. research as of 2019, preliminary clinical research on the potential health effects of a regular high-fiber diet included studies on the risk of several cancers, cardiovascular diseases, and type ii diabetes. a 2011 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 lower risk of death from heart disease, adequate consumption of fiber-containing foods, especially grains, was also correlated with reduced incidence of infectious and respiratory illnesses, and, particularly among males, reduced risk of cancer-related death. a study of over 88,000 women did not show a statistically significant relationship between higher fiber consumption and lower rates of colorectal cancer or adenomas. a 2010 study of 58,279 men found no relationship between dietary fiber and colorectal cancer. an extensive article exploring the link between dietary fiber and inflammatory bowel disease (ibd) described that dietary fiber has significant health benefits for ibd patients 117 a 2022 study over 20 years of japanese adults aged 40–64 years showed a possible inverse relationship between the intake of soluble fiber and the risk of developing dementia during aging. dietary recommendations european union according to the european food safety authority (efsa) panel on nutrition, novel foods and food allergens (nda), which deals with the establishment of dietary reference values for carbohydrates and dietary fibre, "based on the available evidence on bowel function, the panel considers dietary fibre intakes of 25 g per day to be adequate for normal laxation in adults". united states current recommendations from the united states national academy of medicine (nam) (formerly institute of medicine) of the national academy of sciences state that for adequate intake, adult men ages 19–50 consume 38 grams of dietary fiber per day, men 51 and older 30 grams, women ages 19–50 to consume 25 grams per day, women 51 and older 21 grams. these are based on three studies observing that people in the highest quintile of fiber intake consumed a median of 14 grams of fiber per 1,000 calories and had the lowest risk of coronary heart disease, especially for those who ate more cereal fiber. the united states academy of nutrition and dietetics (and, previously ada) reiterates the recommendations of the nam. a 1995 research team'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). the nam's current recommendation for children is 19 g/day for age 1-3 years and 25 g/day for age 4-8 years. 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. 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. the fda classifies which ingredients qualify as being "fiber", and requires for product labeling that a physiological benefit is gained by adding the fiber ingredient. as of 2008, the fda approved health claims for qualified fiber products to display labeling that regular consumption may reduce blood cholesterol levels – which can lower the risk of coronary heart disease – and also reduce the risk of some types of cancer. viscous fiber sources gaining fda approval are: psyllium seed husk (7 grams per day) beta-glucan from oat bran, whole oats, or rolled oats; or whole grain or dry-milled barley (3 grams per day) other examples of bulking fiber sources used in functional foods and supplements include cellulose, guar gum and xanthan gum. other examples of fermentable fiber sources (from plant foods or biotechnology) used in functional foods and supplements include resistant starch, inulin, fructans, fructooligo saccharides, oligo- or polysaccharides, and resistant dextrins, which may be partially or fully fermented. consistent intake of fermentable fiber may reduce the risk of chronic diseases. insufficient fiber in the diet can lead to constipation. united kingdom in 2018, the british nutrition foundation issued a statement to define dietary fiber more concisely and list the potential health benefits established to date, while increasing its recommended daily minimum intake to 30 grams for healthy adults. statement: '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 indigestin ability results in many other indigestible components being isolated along with the carbohydrate components of dietary fiber. these components include resistant starches and oligo saccharides 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. diets naturally high in fiber can be considered to bring about several main physiological consequences: increases fecal bulk and helps prevent constipation by decreasing fecal transit time in the large intestine improves gastro-intestinal health improves glucose tolerance and the insulin response following a meal increases colonic fermentation and short-chain fatty acid production positively modulates colonic microflora reduces hyperlipidemia, hypertension, and other coronary heart disease risk factors increases satiety and hence may contribute to weight management fiber is defined by its physiological impact, with many heterogenous types of fibers. some fibers may primarily impact one of these benefits (i.e., cellulose increases fecal bulking and prevents constipation), but many fibers impact more than one of these benefits (i.e., resistant starch increases bulking, increases colonic fermentation, positively modulates colonic microflora and increases satiety and insulin sensitivity). 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. 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 that are eaten—skin, pulp, seeds, stems, leaves, roots—contain fiber. both insoluble and soluble sources are in those plant components. "carbohydrates" refers to complex carbohydrates, such as long-chained sugars also called starch, oligo saccharides, or poly saccharides, which are sources of soluble fermentable fiber. "resistant to digestion and absorption in the human small intestine" refers to compounds that are not digested by gastric acid and digestive enzymes in the stomach and small intestine, preventing the digesting animal from utilizing the compounds for energy. 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" describes the digestive processes of the large intestine, which comprises a segment called the colon within which additional nutrient absorption occurs through the process of fermentation. fermentation occurs through the action of colonic bacteria on the food mass, producing gases and short-chain fatty acids. these short-chain fatty acids have been shown to have significant health properties. they include butyric, acetic (ethanoic), propionic, and valeric acids. 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, fiber compounds with partial or low fermentability include: cellulose, a poly-saccharide methyl cellulose hemicellulose, a poly-saccharide lignans, a group of phytoestrogens plant waxes fiber compounds with high fermentability include: resistant starches beta-glucans, a group of polysaccharides pectins, a group of heteropolysaccharides natural gums, a group of polysaccharides inulins, a group of polysaccharides oligosaccharides short-chain fatty acids when fermentable fiber is fermented, short-chain fatty acids (scfa) are produced. scfas are involved in numerous physiological processes promoting health, including: 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 scfas that are absorbed by the colonic mucosa pass through the colonic wall into the portal circulation (supplying the liver), and the liver transports them into the general circulatory system. overall, scfas affect major regulatory systems, such as blood glucose and lipid levels, the colonic environment, and intestinal 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 united states fda allows manufacturers 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 regular consumption may reduce the risk of heart disease. the fda statement template for making this claim is: soluble fiber from foods such as , as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. a serving of supplies __ grams of the soluble fiber from necessary per day to have this effect. 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. 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). in december 2016, fda approved a qualified health claim that consuming resistant starch from high-amylose corn may reduce the risk of type 2 diabetes due to its effect of increasing insulin sensitivity. the allowed claim specified: "high-amylose maize resistant starch may reduce the risk of type 2 diabetes. fda has concluded that there is limited scientific evidence for this claim." in 2018, the fda released further guidance on the labeling of isolated or synthetic dietary fiber to clarify how different types of dietary fiber should be classified.