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At least 19 recordsLinked to original sources
PubMedDate not supplied

Importance of enzyme purity and activity in the measurement of total dietary fiber and dietary fiber components.

A study was made of the effect of the activity and purity of enzymes in the assay of total dietary fiber (AOAC Method 985.29) and specific dietary fiber components: resistant starch, fructan, and beta-glucan. In the measurement of total dietary fiber content of resistant starch samples, the concentration of alpha-amylase is critical; however, variations in the level of amyloglucosidase have little effect. Contamination of amyloglucosidase preparations with cellulase can result in significant underestimation of dietary fiber values for samples containing beta-glucan. Pure beta-glucan and cellulase purified from Aspergillus niger amyloglucosidase preparations were used to determine acceptable critical levels of contamination. Sucrose, which interferes with the measurement of inulin and fructooligosaccharides in plant materials and food products, must be removed by hydrolysis of the sucrose to glucose and fructose with a specific enzyme (sucrase) followed by borohydride reduction of the free sugars. Unlike invertase, sucrase has no action on low degree of polymerization (DP) fructooligosaccharides, such as kestose or kestotetraose. Fructan is hydrolyzed to fructose and glucose by the combined action of highly purified exo- and endo-inulinases, and these sugars are measured by the p-hydroxybenzoic acid hydrazide reducing sugar method. Specific measurement of beta-glucan in cereal flour and food extracts requires the use of highly purified endo-1,3:1,4 beta-glucanase and A. niger beta-glucosidase. Beta-glucosidase from almonds does not completely hydrolyze mixed linkage beta-glucooligosaccharides from barley or oat beta-glucan. Contamination of these enzymes with starch, maltosaccharide, or sucrose-hydrolyzing enzymes results in production of free glucose from a source other than beta-glucan, and thus an overestimation of beta-glucan content. The glucose oxidase and peroxidase used in the glucose determination reagent must be essentially devoid of catalase and alpha- and beta-glucosidase.

Aspergillus niger↗
PubMedDate not supplied

Effect of seeds on bile-enzymatic-gravimetric analysis of total dietary fiber.

Dietary fiber sometimes is defined chemically as nonstarch polysaccharides plus lignin or as other specific chemical entities. Analysis of dietary fiber according to a chemical definition typically involves gas chromatography, which allows separation and quantitation of chemical constituents that are added to arrive at a dietary fiber value. Other definitions of fiber are broader, defining it to be whatever is not digested in the alimentary tract. Analytically, this definition translates into the gravimetric sum of the material remaining after a series of enzymatic and chemical treatments that simulate in vivo digestion. Various methods reflect the gravimetric definition, which might include as dietary fiber some protein, resistant starch, and even lipids that are not digested by particular assay conditions. We used a recently proposed bile-enzymatic-gravimetric assay for total dietary fiber on commonly consumed seeds (hulled and unhulled sesame, caraway, and poppy) and visually found these seeds to be undigested. We then determined the impact of the undigested seeds on measured dietary fiber content by spiking homogenized daily menus with 5% by weight of these seeds and calculating recoveries with 2 assumptions: seeds are 100% fiber because they are not digested, and the fiber content of seeds is as determined by assay. Calculated recoveries were very different depending on which assumption was made (71-90% or 99-109%, respectively), and the difference was closely related to the seed's protein content.

Bile↗
PubMed2002

Position of the American Dietetic Association: health implications of dietary fiber.

Dietary fiber consists of the structural and storage polysaccharides and lignin in plants that are not digested in the human stomach and small intestine. A wealth of information supports the American Dietetic Association position that the public should consume adequate amounts of dietary fiber from a variety of plant foods. Recommended intakes, 20-35 g/day for healthy adults and age plus 5 g/day for children, are not being met, because intakes of good sources of dietary fiber, fruits, vegetables, whole and high-fiber grain products, and legumes are low. Consumption of dietary fibers that are viscous lowers blood cholesterol levels and helps to normalize blood glucose and insulin levels, making these kinds of fibers part of the dietary plans to treat cardiovascular disease and type 2 diabetes. Fibers that are incompletely or slowly fermented by microflora in the large intestine promote normal laxation and are integral components of diet plans to treat constipation and prevent the development of diverticulosis and diverticulitis. A diet adequate in fiber-containing foods is also usually rich in micronutrients and nonnutritive ingredients that have additional health benefits. It is unclear why several recently published clinical trials with dietary fiber intervention failed to show a reduction in colon polyps. Nonetheless, a fiber-rich diet is associated with a lower risk of colon cancer. A fiber-rich meal is processed more slowly, which promotes earlier satiety, and is frequently less calorically dense and lower in fat and added sugars. All of these characteristics are features of a dietary pattern to treat and prevent obesity. Appropriate kinds and amounts of dietary fiber for the critically ill and the very old have not been clearly delineated; both may need nonfood sources of fiber. Many factors confound observations of gastrointestinal function in the critically ill, and the kinds of fiber that would promote normal small and large intestinal function are usually not in a form suitable for the critically ill. Maintenance of body weight in the inactive older adult is accomplished in part by decreasing food intake. Even with a fiber-rich diet, a supplement may be needed to bring fiber intakes into a range adequate to prevent constipation. By increasing variety in the daily food pattern, the dietetics professional can help most healthy children and adults achieve adequate dietary fiber intakes.

Cardiovascular Diseases↗
PubMedDate not supplied

What is dietary fiber?

Dietary fiber consists of the remnants of the edible plant cell, polysaccharides, lignin, and associated substances resistant to digestion (hydrolysis) by human alimentary enzymes. This physiological definition has been translated into a chemical method (AOAC Method 985.29), which has recently been shown to miss substances of 10, 11, and 12 degrees of polymerization. It also fails to precipitate some hydrolysis-resistant oligosaccharides which contain many physiological properties expected in dietary fiber, such as inulin and oligofructose, indigestible dextrin (Fibersol-2), galactooligosaccharides and the synthetic polymer polydextrose. The Executive Board of the American Association of Cereal Chemists has appointed a committee to explore the possibility of expanding the definition or chemical methodology for dietary fiber to accommodate components that are not hydrolyzed by human alimentary enzymes, yet have the physiological attributes normally associated with dietary fiber. However, the present review suggests that the current definition is sufficient, along with new methodology, to detect recently discovered components of the dietary fiber complex.

Dietary Fiber↗
PubMed1995

The clinical uses of dietary fiber.

Dietary fiber has received considerable attention in both the popular press and the scientific literature. Fiber is a complex mixture of substances, and research on its effects is difficult to interpret. Dietary fiber has significant gastrointestinal effects, and it is a mainstay of treatment for constipation and hemorrhoids. Insoluble fiber, such as wheat bran, is most effective for treatment of these conditions. Increased intake of soluble dietary fiber appears to benefit patients with diabetes mellitus and hyperlipidemia. High-fiber, low-fat diets have been recommended by a variety of authorities to decrease the incidence of heart disease and certain types of cancer. Any increase in dietary fiber intake should be accompanied by an increase in water intake.

Diabetes Mellitus↗
PubMed1982

Dietary fiber.

Dietary fiber is plant-derived material that is resistant to digestion by human alimentary enzymes. Fiber may be divided into two broad chemical classes: 1) non-alpha-glucan polysaccharides (cellulose, hemicelluloses, and pectins) and 2) lignins. Dietary fiber behaves within the gastrointestinal tract as a polymer matrix with variable physicochemical properties including susceptibility to bacterial fermentation, water-holding capacity, cation-exchange, and adsorptive functions. These properties determine physiological actions of fiber and are dependent on the physical and chemical composition of the fiber. Fiber undergoes compositional changes as a consequence of bacterial enzymatic action in the colon. Dietary fiber is of clinical significance in certain disorders of colonic function and in glucose and lipid metabolism. Dietary fiber increases stool bulk by acting as a vehicle for fecal water and by increasing fecal bacterial volume. Use of fiber in the treatment of constipation and uncomplicated diverticular disease is well established. By increasing stool bulk, fiber also reduces the fecal concentration of bile acids and other substances. Certain types of fiber decrease the rate of glucose absorption and attenuate postprandial rises in blood glucose and insulin. Plasma cholesterol levels are reduced by mucilaginous forms of fiber. This effect appears to be mediated in part by an increase in fecal acidic sterol excretion.

Adsorption↗
PubMed1979

Relationships among crude fiber, neutral detergent fiber, in vitro dietary fiber, and in vivo (rats) dietary fiber in wheat foods.

The in vivo dietary fiber contents of wheat milling fractions and wheat foods, determined in rat feeding experiments, were compared with dietary fiber values determined in vitro with pronase alpha-amylase digestion. Both types of dietary fiber values were compared with crude fiber and neutral detergent fiber values in the same materials. Regression analyses indicated close correlation amongst all values determined. It appears that laboratory analysis for crude fiber, neutral detergent fiber, or in vitro dietary fiber accurately predicts in vivo dietary fiber (rats) for wheat milling fractions when the laboratory result is adjusted by means of an appropriate regression equation.

Animals↗
PubMed1988

Alterations in colonic thymidine kinase enzyme activity induced by consumption of various dietary fibers.

Dietary fibers may tend to enhance or inhibit chemically induced experimental colon cancer, depending on the particular fiber consumed. This study examined the relationship between colonic thymidine kinase enzyme activity and mucin histochemistry and the reported effects of various dietary fibers on chemically induced colon carcinogenesis. Fiber-supplemented diets containing fibers reported to inhibit (wheat bran) or enhance (guar gum, carrageenan) chemically induced colon carcinogenesis in the rat were selected. Four groups of male Fischer 344 rats consumed 10% wheat bran, 5% guar gum, 5% carrageenan, or fiber-free diets ad libitum for 4 weeks. At the completion of the treatment period, the distal 12 cm of colonic mucosa was scraped off and homogenized for determination of thymidine kinase activity, and a 0.5-cm section of midcolon was processed by the high-iron diamine/Alcian blue method for mucin histochemistry. Final animal weights did not differ significantly among groups. Thymidine kinase enzyme specific activity (mumole thymidine phosphate formed x 10(6)/min/mg protein, means +/- SEMs) was not significantly different in the fiber-free, wheat bran, and guar gum groups (10.98 +/- 1.50, 7.41 +/- 1.09, and 9.11 +/- 2.04, respectively) but was markedly elevated at 41.84 +/- 4.65 in the carrageenan group (alpha less than 0.001). Mucin histochemistry failed to reveal any significant differences among dietary groups.

Animals↗
PubMed1989

Dietary fiber and giardiasis: dietary fiber reduces rate of intestinal infection by Giardia lamblia in the gerbil.

Gerbils were maintained on a low-fiber (5%) or a high-fiber (20%) diet in which the major fiber source was cellulose. Animals in the low-fiber diet group were significantly more likely to become infected when inoculated with 100 Giardia lamblia cysts than were animals in the high-fiber group. No differences were detected in gastrointestinal transit, gastric, and small intestinal luminal pH, or in duodenal mucus blanket acidic glycoprotein between animals in the high- and the low-fiber diet groups at the time of cyst inoculation. The fiber content of the diet after cyst inoculation determined the infection rate. These data suggest that the dietary fiber effect occurred during trophozoite colonization of the small intestine. When infected animals on the low-fiber diet were placed on the high-fiber diet for 24 hr, trophozoite clearing occurred in the lower small intestine. In the jejunum, the number of trophozoites attached to the mucosal surface decreased, while the number associated with luminal mucus increased. We conclude that the fiber-induced mucus secretion and the bulk movement of the insoluble fiber reduced the attachment of trophozoites to the intestinal mucosa, which decreased the probability of trophozoites establishing and sustaining colonization of the mucosa.

Animals↗
PubMed2006

Dietary fiber intake, dietary glycemic load, and the risk for gestational diabetes mellitus.

OBJECTIVE: We aimed to examine whether pregravid dietary fiber consumptions from cereal, fruit, and vegetable sources and dietary glycemic load were related to gestational diabetes mellitus (GDM) risk. RESEARCH DESIGN AND METHODS: This study was a prospective cohort study among 13,110 eligible women in the Nurses' Health Study II. GDM was self-reported and validated by medical record review in a subsample. RESULTS: We documented 758 incident GDM cases during 8 years of follow-up. After adjustment for age, parity, prepregnancy BMI, and other covariates, dietary total fiber and cereal and fruit fiber were strongly associated with GDM risk. Each 10-g/day increment in total fiber intake was associated with 26% (95% CI 9-49) reduction in risk; each 5-g/day increment in cereal or fruit fiber was associated with a 23% (9-36) or 26% (5-42) reduction, respectively. Dietary glycemic load was positively related to GDM risk. Multivariate relative risk for highest versus lowest quintiles was 1.61 (1.02-2.53) (P for trend 0.03). The combination of high-glycemic load and low-cereal fiber diet was associated with 2.15-fold (1.04-4.29) increased risk compared with the reciprocal diet. CONCLUSIONS: These findings suggested that prepregnancy diet might be associated with women's GDM risk. In particular, diet with low fiber and high glycemic load was associated with an increased risk. Future clinical and metabolic studies are warranted to confirm these findings.

Adult↗
PubMed1978

Interaction of dietary fiber with other dietary components: a possible factor in certain cancer etiologies.

Dietary fiber is a highly interacting dietary component and is made up of a wide variety of enzyme-indigestible polymers: cellulose, pectins, gums, mucilages, lignin, and water-insoluble hemicelluloses. The study of the effect of dietary fiber on prevention of cancer, specifically of colonic cancer, cannot be carried on without considering that: 1) various types of dietary fiber have different metabolic effect; 2) other components of the diet (e.g., amount of fat) may influence the way dietary fiber affects the colonic environment; 3) the overall effect of dietary fiber may be the sum of effects on fecal bulk, colonic microflora pattern and metabolites, dilution of carcinogens, colonic pH, transit time, alteration of nutrient absorption, and postprandial hormonal function. It is unlikely that dietary fiber can be studied in isolation in experimental diets unless great care is taken to consider all interactions with other dietary components.

Cellulose↗
PubMed1997

Dietary fiber and colorectal cancer risk.

We conducted a population-based case-control study among different ethnic groups in Hawaii to evaluate the role of various types and components of fiber, as well as micronutrients and foods of plant origin, on the risk of colorectal cancer. We administered personal interviews to 698 male and 494 female Japanese, Caucasian, Filipino, Hawaiian, and Chinese cases diagnosed during 1987-1991 with adenocarcinoma of the colon or rectum and to 1,192 population controls matched to cases by age, sex, and ethnicity. We used conditional logistic regression to estimate odds ratios, adjusted for caloric intake and other covariates. We found a strong, dose-dependent, inverse association in both sexes with fiber intake measured as crude fiber, dietary fiber, or nonstarch polysaccharides. We found inverse associations of similar magnitude for the soluble and insoluble fiber fractions and for cellulose and noncellulosic polysaccharides. This protective effect of fiber was limited to fiber from vegetable sources, with an odds ratio of 0.6 (95% confidence interval = 0.4-0.9) and 0.5 (95% confidence interval = 0.3-0.7) for the highest compared with the lowest quartile of intake for men and women, respectively. We found associations of the same magnitude for soluble and insoluble vegetable fiber, but no clear association with fiber from fruits or cereals. This pattern was consistent between sexes, across segments of the large bowel (right colon, left colon, and rectum), and among most ethnic groups. The effect of vegetable fiber may be independent of the effects of other phytochemicals, since the effect estimates remained unchanged after further adjustment for other nutrients. Intakes of carotenoids, light green vegetables, yellow-orange vegetables, broccoli, corn, carrots, bananas, garlic, and legumes (including soy products) were inversely associated with risk, even after adjustment for vegetable fiber. The data support a protective role of fiber from vegetables against colorectal cancer, which appears independent of its water solubility property and of the effects of other phytochemicals. The data also indicate that certain vegetables and fruits may be protective against this disease through mechanisms other than their fiber content.

Adenocarcinoma↗
PubMedDate not supplied

Inulin and oligofructose are part of the dietary fiber complex.

Dietary fiber has been defined as the remnants of plant cells resistant to hydrolysis by human alimentary enzymes. Its main chemical constituents are hemicelluloses, celluloses, lignin, pectins, gums, and waxes. The U.S. Food and Drug Administration and the U.S. Department of Agriculture determine compliance with nutritional labeling regulations for dietary fiber by use of the existing AOAC INTERNATIONAL methods for total dietary fiber. The above compounds are readily detected by these methods. However, some oligo- and polysaccharides are resistant to human alimentary enzymes and do not precipitate in 78% ethanol, the usual reagent for precipitating dietary fiber in analytical procedures. Some of these saccharides, termed fructans, are inulin and oligofructose. They possess many physiological attributes normally associated with dietary fiber. Inulin is a mixture of oligo- and polysaccharides composed of fructose moieties joined by beta(2-->1) linkages in linear chains. Almost each chain ends with a glucose moiety. Oligofructose is a synonym for fructo-oligosaccharides, with fructose moieties joined by beta(2-->1) linkages, as in inulin. Not all molecules have a glucose unit, and the chain length is less than 10 units. A method for inulin and oligofructose was developed and approved official first action by AOAC INTERNATIONAL in early 1997. It involves extraction of sample and treatment of the extract with amyloglucosidase followed by fructozyme (Fructozyme Enzyme Process Division, Novo Nordisk, Novo Industry, Copenhagen, Denmark). The sugars released in each of the 3 steps are measured by anion-exchange chromatography. The concentration of fructans is calculated as the difference of sugars, glucose and fructose, after the enzymatic treatments and the initial sample. The repeatability standard deviations for inulin and oligofructose ranged from 2.9 to 5.8% and the reproducibility standard deviations ranged from 4.7 to 11.1%. The method was accepted by AOAC INTERNATIONAL.

Dietary Fiber↗
PubMedDate not supplied

Inconsistent differences between neutral detergent fiber and total dietary fiber values of fruits and vegetables.

A large number of fruits and vegetables were analyzed to determine levels of neutral detergent fiber (NDF) and total dietary fiber (TDF). The results showed that the TDF method is more precise than the NDF method. Further, the NDF values are significantly higher than the TDF values for apples and for miscellaneous fruits and vegetables, and significantly lower for stonefruit. For berryfruit, the differences between the NDF and TDF data are not significant. Also, a significant interaction between sample and method (except for berryfruit) indicated that, within groups, the (TDF-NDF) values vary so much that a "group difference" does not exist; consequently, figures from one method cannot be estimated from results of the other.

Dietary Fiber↗
PubMed1978

Nutritional implications of dietary fiber.

When dietary fiber intakes are increased by supplementing diets with bran and whole wheat products, then fecal fat, nitrogen, energy, and mineral excretion rise. These changes suggest that fiber may be altering normal digestive and absorptive function. Recent studies have confirmed this and have also shown that fiber of different composition and from contrasting sources produces different physiological effects. The gel-forming polysaccharides such as guar gum and pectin alter the pattern of glucose absorption and are hypocholesterolemic; fiber from cereals is not hypocholesterolemic but exerts a pronounced effect on the large gut. Dietary fiber is largely digested in the colon by the microflora and so influences colonic function, fecal weight, and composition. The significance of the changes in fat, nitrogen, and energy output remains to be evaluated, but the impairment of mineral absorption--particularly of calcium, zinc, and iron--by fiber gives cause for concern. Fiber must now be considered with other dietary constituents in all nutritional studies.

Calcium↗
PubMed2004

Antioxidative activity of animal and vegetable dietary fibers.

Some dietary fibers originated from insects such as silkworm (Sericin) and others along with constituents of several representative seaweeds such as wakame Undaria pinnatifida; hijiki Hizikia fusifome; and kombu Laminaria japonica, were found to have fairly large reaction rates determined by quenching experiments of emission spectra in the near-infrared region lambdamax 1270 nm for singlet oxygen 1O2, Cypridina luminescence method for superoxide, and peroxide value (POV) for autoxidation. The determined reaction rates are between 10(3)-10(5) (g/L)(-1) s(-1) for the insect and the plant dietary fibers; the larger ones are as large as that of ascorbic acid, 1.93 x 10(4) (g/L)(-1) s(-1) for singlet oxygen. Most of these seaweed constituents also showed antioxidative activity against autoxidation and superoxide as well as their immunological enhancing activity. These results suggest a possibility that dietary fibers that are supposed to prevent the large-intestine cancer by their physical properties may prevent the cancer, at least in parts, by their chemical, antioxidative activity.

Animals↗