Rate and extent of digestion of the ethanol-soluble and neutral detergent-insoluble fractions of corn grain.
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The objectives of this study were to partition corn grain into three digestible fractions and to measure the rate of disappearance of these fractions in vitro. Seventeen corn grain samples with varied fiber concentrations were extracted with either 80% ethanol or neutral detergent to obtain estimates of the pool size and digestion kinetics of the A, B1, B2, and C fractions. The carbohydrate soluble in 80% ethanol averaged only 2.6+/-.3% of the DM, although 80% ethanol extracted 7.1+/-1.2% of DM of corn grain. The ethanol-soluble fraction of corn grain contained protein, ether-extractable compounds, and a small amount of ash in addition to carbohydrate. Because of this chemical heterogeneity and because of the small size of the ethanol-soluble fraction, it was not possible to determine the digestion rate of this fraction by measuring gas production. The NDF content of the corn grain was 10.6+/-.7% of DM and was highly digestible (94.6+/-1.4%). The digestible NDF contributed 9.5% of the total gas production from corn grain. Because the size, digestibility, and digestion rate of the digestible NDF fraction varied little among corn grain samples, it is not necessary to routinely analyze the digestion kinetics of the digestible NDF fraction of dried corn grain. An average gas production curve of this fraction can be used as a base to subtract from the total gas production curve to generate the gas production curve of the neutral detergent-soluble fraction for dried, ground corn grain samples. (+info)
Dietary antioxidant vitamins and fiber in the etiology of cardiovascular disease and all-causes mortality: results from the Scottish Heart Health Study.
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In this paper, data obtained between 1984 and 1993 from 11,629 men and women as part of the Scottish Heart Health Study (Scotland, United Kingdom) were used to investigate the relation between antioxidant vitamin and fiber intakes and both incident coronary heart disease (CHD) (649 events) and all-causes mortality (591 deaths). All age-adjusted mean intakes tended to be higher in the group that experienced no event. For men, increased fiber intake was associated with decreased risk of CHD even after adjustment for a host of other major coronary risk factors; hazard ratios relative to the lowest quarter were 0.68, 0.70, and 0.64 by increasing quarter. This relation was also observed for mortality (hazard ratios of 0.62, 0.66, and 0.62). Evidence was found that higher intakes of the antioxidants were also beneficial, although the associations were weaker. For women, fiber was the only obviously influential dietary factor, with hazard ratios of 0.94, 0.60, and 0.56 for CHD and 1.25, 0.82, and 0.65 for mortality. These results suggest that the current public health drive to increase the consumption of foods rich in antioxidant vitamins and (particularly) fiber will impact on both CHD risk and the general health of the population. (+info)
Some dietary fibers reduce the absorption of carotenoids in women.
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Dietary fiber may be partly responsible for the lower bioavailability of carotenoids from food than from purified supplements. Due to the lack of detailed information available, we investigated the effects of different kinds of dietary fiber on the absorption of carotenoids and alpha-tocopherol. Six healthy young women received an antioxidant mixture consisting of beta-carotene, lycopene, lutein, canthaxanthin and alpha-tocopherol together with a standard meal. The meal did not contain additional dietary fiber or was enriched with pectin, guar, alginate, cellulose or wheat bran (0. 15 g. kg body weight(-1)). The increases in plasma carotenoid and alpha-tocopherol concentrations were followed over 24 h, and the areas-under-curves (AUC(24h)) were calculated. The mean AUC(24h) of beta-carotene was significantly (P < 0.05) reduced by the water-soluble fibers pectin, guar and alginate with a mean decrease of 33-43%. All tested fibers significantly reduced the AUC(24h) of lycopene and lutein by 40-74% (P < 0.05). The dietary fiber effect on the AUC(24h) of canthaxanthin was almost significant (P = 0.059) and there was no effect on the AUC(24h) of alpha-tocopherol. We conclude that the bioavailability of beta-carotene, lycopene and lutein given within a mixed supplement is markedly reduced by different kinds of dietary fiber. (+info)
Studies on the mechanism of cancer protection by wheat bran: effects on the absorption, metabolism and excretion of the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ).
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We examined ways in which dietary supplements of wheat bran may protect against colon cancer. The effects of supplementing the diet of female Wistar rats with 10% wheat bran on the disposition and metabolism of the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) labelled with (14)C was determined. Our data show that the wheat bran had a major effect on both the distribution and metabolism of IQ. At a low dose of IQ (1 mg/kg), we unexpectedly found that up to 2 h after gavage there were higher concentrations of radioactivity in the plasma of rats fed wheat bran compared with the controls, but there were lower concentrations of radioactivity after 2 h. At a high dose of IQ (50 mg/kg), there were always lower concentrations of radioactivity in the plasma of rats fed wheat bran compared with the control rats. One of the most marked effects of wheat bran was apparently to significantly retard the metabolism of IQ in the plasma when this was fed at either dose. There were also differences between the rats fed wheat bran and the control in the concentrations and types of IQ metabolites in the urine. (+info)
A diet high in fat and meat but low in dietary fibre increases the genotoxic potential of 'faecal water'.
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To determine the effects of different diets on the genotoxicity of human faecal water, a diet rich in fat, meat and sugar but poor in vegetables and free of wholemeal products (diet 1) was consumed by seven healthy volunteers over a period of 12 days. One week after the end of this period, the volunteers started to consume a diet enriched with vegetables and wholemeal products but poor in fat and meat (diet 2) over a second period of 12 days. The genotoxic effect of faecal waters obtained after both diets was assessed with the single cell gel electrophoresis (Comet assay) using the human colon adenocarcinoma cell line HT29 clone 19a as a target. The fluorescence and length of the tails of the comet images reflects the degree of DNA damage in single cells. The mean DNA damage, expressed as the ratio of tail intensity (fluorescence in the tail) to total intensity of the comet after incubation with faecal water from volunteers consuming diet 1 was about twice as high as for diet 2. The susceptibility of the cells incubated with faecal water to DNA damage caused by additional hydrogen peroxide treatment showed no significant differences between the two diets. Generation of oxidized pyrimidine and purine bases revealed no differences after pretreatment with both types of faecal water. The results indicate that diets high in fat and meat but low in dietary fibre increase the genotoxicity of faecal water to colonic cells and may contribute to an enhanced risk of colorectal cancer. (+info)
Short-chain fatty acid metabolism, apoptosis, and Apc-initiated tumorigenesis in the mouse gastrointestinal mucosa.
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Short-chain fatty acids (SCFAs) are physiological regulators of growth and differentiation in the gastrointestinal tract, and we have previously shown that apoptosis induced in colonic cell lines by these compounds is dependent on their metabolism by B-oxidation in the mitochondria (B. G. Heerdt et al., J. Biol. Chem., 266: 19120-19126, 1991; Cancer Res., 54: 3288-3293, 1994). Because tumors initiated by an inherited Apc mutation have been reported to be linked to decreases in apoptosis in the flat mucosa of the gastrointestinal tract, the aims were to determine whether elimination of efficient metabolism of SCFAs affected apoptosis in the gastrointestinal mucosa of the mouse, and whether this altered tumorigenesis initiated by an inherited Apc mutation. We, therefore, generated mice that have a chain-terminating mutation in the Apc gene and that were either wild-type for SCFA metabolism, or deficient, due to homozygous deletion of the gene (Scad) that encodes the enzyme short-chain acyl dehydrogenase, which catalyzes the first step in SCFA B-oxidation. Scad+/+ mice maintained on a wheat bran-fiber-supplemented diet gained significantly more weight than mice maintained on AIN76A, but this was eliminated by the Scad mutation, demonstrating that uptake and metabolism of SCFAs in the gastrointestinal tract can be a significant energy source. As predicted, on either AIN76A or wheat bran diet, the Scad mutation almost completely eliminated apoptosis in the flat mucosa of the proximal colon and reduced apoptosis by 50% in the distal colon compared with littermates that were wild-type for Scad. The mutation also reduced apoptosis by approximately 50% in the duodenum in AIN76A-fed mice. These reductions in apoptosis had no effect on incidence, frequency, or site specificity of tumors initiated by the Apc mutation. Therefore, the metabolism of SCFAs by the gastrointestinal mucosa plays a role in modulating apoptosis, but a general decrease in apoptosis in the mucosa of the gastrointestinal tract is not linked to gastrointestinal tumorigenesis initiated by an inherited Apc mutation. (+info)
Diet and cancer prevention: the fiber first diet.
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Diet can play a major role in cancer prevention. The international differences in cancer incidence are largely accounted for by lifestyle practices that include nutrition, exercise, and alcohol and tobacco use. About 50% of cancer incidence and 35% of cancer mortality in the U.S., represented by cancers of the breast, prostate, pancreas, ovary, endometrium, and colon, are associated with Western dietary habits. Cancer of the stomach, currently a major disease in the Far East, relates to distinct, specific nutritional elements such as excessive salt intake. For these cancers, information is available on possible initiating genotoxic factors, promoting elements, and prophylactic agents. In general, the typical diet in the United States contains low levels of the potent carcinogenic agents, heterocyclic amines, formed during the cooking of meats. It provides only about half the potent appropriate fiber intake and is high in calories. About twice as many calories as would be desirable come from fat, certain kinds of which enhance the development of cancers. Other foods with functional properties, such as soy products and tea, can be beneficial. To achieve reduction in risk of certain cancers, diet must be optimized, primarily to reduce caloric intake and the fat component. The latter should be 20% or less of total caloric intake and fiber should be increased to 25-35 g per day for adults. One approach to achieving these goals is the Fiber First Diet, a diet designed around adequate fiber intake from grains, especially cereals, vegetables, legumes, and fruits, which thereby reduces both calorie and fat intake. Such dietary improvements will not only reduce cancer and other chronic disease risks, but will contribute to a healthy life to an advanced age. A corollary benefit is a lower cost of medical care. (+info)
Mucin secretion is modulated by luminal factors in the isolated vascularly perfused rat colon.
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BACKGROUND: Mucins play an important protective role in the colonic mucosa. Luminal factors modulating colonic mucus release have been not fully identified. AIM: To determine the effect of some dietary compounds on mucus discharge in rat colon. METHODS: An isolated vascularly perfused rat colon model was used. Mucus secretion was induced by a variety of luminal factors administered as a bolus of 1 ml for 30 minutes in the colonic loop. Mucin release was evaluated using a sandwich enzyme linked immunosorbent assay supported by histological analysis. RESULTS: The three dietary fibres tested in this study (pectin, gum arabic, and cellulose) did not provoke mucus secretion. Luminal administration of sodium alginate (an algal polysaccharide used as a food additive) or ulvan (a sulphated algal polymer) induced a dose dependent increase in mucin discharge over the concentration range 1-25 mg/l (p<0.05 for 25 mg/l alginate and p<0.05 for 10 and 25 mg/l ulvan). Glucuronic acid and galacturonic acid, which are major constituents of a variety of fibres, produced significant mucin secretion (p<0.05). Hydrogen sulphide and mercaptoacetate, two sulphides produced in the colonic lumen by microbial fermentation of sulphated polysaccharides, did not modify mucin secretion. Among the short chain fatty acids, acetate (5-100 mM) induced a dose dependent release of mucus (p<0.05 for 100 mM acetate). Interestingly, butyrate at a concentration of 5 mM produced colonic mucin secretion (p<0.05), but increasing its concentration to 100 mM provoked a gradual decrease in mucus discharge. Propionate (5-100 mM) did not induce mucin release. Several dietary phenolic compounds (quercetin, epicatechin, resveratrol) did not provoke mucus discharge. CONCLUSIONS: Two algal polysaccharides (alginate and ulvan), two uronic acids (glucuronic acid and galacturonic acid), and the short chain fatty acids acetate and butyrate induce mucin secretion in rat colon. Taken together, these data suggest that some food constituents and their fermentation products may regulate the secretory function of colonic goblet cells. (+info)