Analysis of fiber components.
Explore the source record for details and available documents.
Chromatography, Gas↗
Biomedical subjects
J L Slavin
Publications and source records attributed to J L Slavin.
Comparison of dye and pellet gastrointestinal transit time during controlled diets differing in protein and fiber levels.
The purpose of this experiment was to compare repeated measurements of the gastrointestinal transit times of simultaneously ingested dye and radiopaque pellets. Pellet transit was calculated as the time required for 80% of the dose to excreted and as mean transit time (MTT-S). comparisons were made in seven healthy women during three controlled diet periods, two containing different levels of protein and the third added fiber (16 g refined cellulose). Each experimental period was about on month. Dietary protein level or phases of the menstrual cycle had no significant effect on gastrointestinal transit time. Cellulose consumption also did not significantly affect transit time, but it did reduce the variability between repeated 80% transit determinations in four subjects, between MTT-S in three subjects, and between dye in two subjects. The two different measures of pellet transit, 80% pellets and MTT-S, and the dye were significantly correlated, although the correlations were generally stronger during the cellulose diet period. These results suggest that the menstrual cycle, refined cellulose, and dietary protein level have limited effects on gastrointestinal transit time and that measurement of transit as passage of 80% pellets and MTT-S are comparable.
Adult↗
Limits of predicting gastrointestinal transit time from other measures of bowel function.
The two aims of these experiments were first, to examine the relationships between mean daily stool weight, mean weight per stool, frequency of defecation, dye transit time, dietary fiber intake, and transit time of small radiopaque pellets, and second, to determine the ability of these measures of bowel function, singly or in combination, to predict gastrointestinal transit time of the pellets. Variables were observed simultaneously in 13 healthy women consuming controlled low and high cellulose diets. All except one of the correlation coefficients between the measures of bowel function were significant. Stepwise regression analysis retained log stool weight, fiber and dye transit to predict log of the mean transit time of all pellets (R2 = 71.3); the same three variables were selected to predict log of the transit time of 80% of the pellets (R2 = 59.4). Mean daily stool weight explained about 50% of the variation for both measures of transit, while dye transit and dietary fiber explained the rest. Log transformation of either stool weight or pellet transit time or both variables improved the prediction of about 10%. These results suggest that prediction of pellet gastrointestinal transit time from other measures of bowel function may be limited and is influenced significantly by the fiber level of the diet.
Adult↗
Apparent digestibility of neutral detergent fiber in elderly and young adults.
These experiments assessed the ability of the neutral detergent fiber (NDF) method to remove starch and nitrogen from food NDF residues, and nitrogen and endogenous secretions from fecal NDF residues; and compared indices of bowel function, including apparent NDF digestibility, of nine elderly subjects to those of six young women. Subjects consumed similar, controlled "low fiber" diets containing foods typically eaten in the United States. Nitrogen and starch contents of food composite NDF were determined in NDF obtained by the hog alpha amylase modification of the Van Soest procedure, whereas the nitrogen content of fecal NDF was determined using NDF obtained by the unmodified procedure. The modified Van Soest method adequately removed nitrogen and starch from food NDF, but fecal NDF contained nitrogen. Both groups digested the majority of the NDF, 63 and 70% for the elderly and young subjects, respectively. Apparent fiber digestibility, which was measured several times in each subject, increased to 69 and 75% for the two groups, respectively, when a correction was made for the nitrogen in the fecal NDF. Mean gastrointestinal transit time and frequency of defecation of the two age groups were comparable, whereas mean daily wet and dry stool weights of the elderly were larger than those of the young women. These results suggest that the bowel of the elderly may function as well as that of the young adult.
Adult↗
Neutral detergent fiber, hemicellulose and cellulose digestibility in human subjects.
The fate of dietary fiber and its components was examined in seven women consuming low cellulose (LC) and high cellulose (HC) diets, each for about 1 month. The diets were of constant daily composition and differed only in that the HC diet contained an additional 16 g/day non-nutritive fiber (Solka Floc), which increased the neutral detergent fiber (NDF) of the diet from 9.5 to 23.5 g/day and Crampton and Maynard cellulose from 5.4 to 19.3 g/day. When apparent fiber digestibilities during 5-day periods were determined, both NDF and cellulose digestibilities varied greatly and inconsistently in each subject throughout both diet periods. Therefore, samples were pooled to form a single 20-30 day composite for each subject during each diet. Mean apparent NDF digestibility, after correcting for protein contamination in fecal NDF, was 70.4 +/- 7.3% during the LC diet and decreased to 23.0 +/- 15.0% during the HC diet. Cellulose digestibility was 69.7 +/- 10.7% without and 15.7 +2- 17.4% with the added cellulose. Hemicellulose was calculated as NDF minus cellulose. When the fecal NDF was corrected for protein contamination, hemicellulose digestibility averaged 71.7 +/- 5.4% during the LC diet and 51.0 +/- 7.9% during the HC diet. In a separate experiment, 16 g/day Solka Floc was ingested with a semi-purified liquid diet and only 8% of the cellulose was digested. These results suggest that more than half of the fiber in a LC diet containing fruits, vegetables and refined grains is degraded, while the apparent digestibility of refined cellulose is minimal.
Adult↗
Influence of refined cellulose on human bowel function and calcium and magnesium balance.
The effect of cellulose purified from wood pulp on wet and dry stool weights, gastrointestinal transit time (TT), frequency of defecation, and calcium and magnesium balances was tested. Seven healthy women consumed a low fiber diet of constant composition (percentage of total kcal: 23% protein, 30% fat, 47% carbohydrate) and the same metabolically controlled diet to which 16 g of refined cellulose (Solka Floc) was added. Each diet was consumed for approximately one month. The neutral detergent fiber contents of the two diets were 9.5 and 23.5 g, respectively. Cellulose consumption significantly increased mean daily wet stool weight from 74.6 +/- 23.4 (SD) to 130.5 +/- 29.4 g, mean daily dry fecal weight from 19.1 +/- 4.2 to 39.5 +/- 7.7 g, and frequency of defecatin from 0.85 +/- 0.2 to 1.10 +/- 0.29/day. Cellulose effectively shortened TT of two subjects with initially slow TT (7 days), but mean TT of all subjects was not significantly affected when fiber was added to the diet. Fecal excretions of calcium and magnesium were significantly greater when the diet containing cellulose was fed, and only calcium balance was significantly more negative. These results suggest that moderate levels of refined cellulose adversely increased fecal losses of calcium and magnesium. All other indices of bowel function remained within normal ranges.
Adult↗
Effect of refined cellulose on apparent energy, fat and nitrogen digestibilities.
Seven young women consumed a low cellulose diet for about 1 month and then the same diet for an additional month except that 16 g/day Solka Floc was added to the diet. Apparent digestibilities of energy, fat and nitrogen were measured for each subject during each diet. Digestibilities of fat and nitrogen were not affected by refined cellulose ingestion. Digestibility of nitrogen was 93.2% without and 92.9% with the Solka Floc, while fat digestibility was 96.3% during the control diet and 95.4% during the high cellulose diet. Mean digestibility of gross energy decreased significantly when cellulose was added to the diet, from 95.4% to 92.0% (P < 0.01). Undigested fecal fiber was the major source of the increased fecal energy. When fecal fiber energy was subtracted from total fecal energy and apparent energy digestibility recalculated, there was no difference in apparent energy digestibility during the 2 diets, 96.1% without and 95.6% with the Solka Floc supplement. Thus, ingestion of 16 g/day Solka Floc had no detrimental effect on the utilization of nitrogen and fat and increases in fecal energy could be explained by undigested refined cellulose.
Adult↗
Evaluation of high-performance liquid chromatography for measurement of the neutral saccharides in neutral detergent fiber.
Explore the source record for details and available documents.
Chromatography, High Pressure Liquid↗
Bowel function of healthy men consuming liquid diets with and without dietary fiber.
The importance of the level of dietary fiber intake on bowel function was measured in 16 healthy young males consuming self-selected and liquid enteral diets. Subjects consumed liquid Ensure as their sole nutrient source plus 0 (diet a), 30 (diet c), and 60 (diet d) g/day soy fiber, a fiber source high in hemicellulose that was added to the Ensure. Further, to examine whether heat processing affects the physiologic action of fiber, subjects consumed Enrich, an enteral formula similar to Ensure, which contains 30 g of the same soy fiber (diet b). The four diets were consumed in randomized order each for 10 days. Daily wet stool weight averaged 144.6 g on the self-selected diet and decreased significantly to 67.3 g when Ensure was consumed alone. Average stool weights on diets (b), (c), and (d) were 114.6, 100.2, and 150.3 g/day, respectively. Average fecal dry weights for the four diets were 19.1, 28.7, 25.0, and 30.3 g/day for (a-d), respectively. Gastrointestinal transit time, as measured with radiopaque pellets, was longest on the Ensure diet, 72.4 hr, and approximately 2 days on the fiber-supplemented diets and the self-selected diet. Thus, soy fiber's physiologic effect on laxation was not changed by heat processing. Also, although stool weights were larger on higher fiber intakes, transit rates were similar on all the fiber-containing diets.
Adult↗
Determination of the fiber content of enteral feedings.
The importance of dietary fiber in maintaining optimum bowel function has been shown in feeding studies, and many enteral formulas now contain dietary fiber, usually as soy polysaccharide (SP). Generally only total dietary fiber (TDF) values are given on the label or in product literature, with no indication of insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) content. Often product literature highlights the amount of SP contained in the formula, not the TDF. The method used to determine TDF content usually is not specified, making it impossible to compare products on a TDF basis. We compared the dietary fiber content of commercially available enteral formulas objectively to help clinicians make informed choices when selecting fiber-containing formulas. Fiber-containing formulas by suppliers were freeze-dried and total, water-soluble, and water-insoluble dietary fiber measured by the Association of Official Analytical Chemists (AOAC) approved method. TDF per 1000 mL ranged from 4.0 to 9.9 g for blenderized formulas and from 7.2 to 20.3 g in formulas containing SP. IDF values per 1000 mL ranged from 2.0 to 5.4 g for blenderized product, and the soy formulas ranged from 5.5 to 16.9 g. SDF values per 1000 mL ranged from 2.0 to 4.5 g in blenderized products, and in soy formulas SDF ranged from 1.7 to 3.8 g. Differences in physiological effects of fiber-containing enteral formulas may be because of differences in fiber composition.
Dietary Fiber↗
Gastrointestinal effects of modified guar gum and soy polysaccharide as part of an enteral formula diet.
Dietary fiber supplementation may improve gastrointestinal tolerance and decrease diarrhea in patients receiving enteral formula diets. To compare the effects of two dietary fibers on bowel function parameters and short-chain fatty acid excretion we fed 11 healthy men three defined enteral formula diets in random order for 18 days each. The test diets consisted of a fiber-free formula and daily intakes of maltodextrin (0 g of fiber), 15 g of total dietary fiber as an enzymatically modified guar gum, and 15 g of total dietary fiber as soy polysaccharide. Data were also collected while subjects consumed self-selected diets for 5 days. Mean transit time was longer and fecal moisture content was lower on 0 g of fiber and modified guar than on the self-selected and soy diets. Furthermore, mean transit time was slightly longer and fecal nitrogen excretion greater on modified guar compared with 0 g of fiber. Daily fecal output and frequency of defecation were greater, fecal pH was lower, and fecal butyrate concentrations were higher on the self-selected diet compared with the enteral formula diets. However, there was no difference in these parameters among the three liquid diets. Thus, despite significant differences in mean transit time, few differences in other parameters of bowel function were observed when healthy subjects consumed enteral formula diets containing 0 g of fiber and 15 g of total dietary fiber as modified guar and soy.
Adult↗
Apparent fiber digestibility and fecal short-chain fatty acid concentrations with ingestion of two types of dietary fiber.
Short-chain fatty acids (SCFAs) are products of dietary fiber fermentation. As such, fiber digestibility is thought to be related to SCFA production. The effects of two concentrations of cereal fiber as wheat bran (WB) and vegetable fiber (VF) on fiber digestibility were examined in 34 free-living volunteers. Five diets consisting of a fiber-free liquid nutrition supplement and quick breads containing either (1) 0 g of fiber, (2) 10 g of WB, (3) 30 g of WB, (4) 10 g of VF, or (5) 30 g of VF were consumed in random order. Apparent digestibility of neutral detergent fiber (NDF) was determined. Colonic fluid, collected by in vivo dialysis in 9 subjects, was analyzed for SCFAs by gas chromatography. Digestibility of NDF was greater with WB than with VF ingestion in those 9 subjects, but digestibility was not different with ingestion of both fibers when all 34 subjects were considered. No effect of intake level was seen with either WB or VF. Fiber ingestion increased acetate, propionate, and butyrate concentrations above those on the 0 g of fiber diet (43%, 31%, and 90%, respectively; p < .0001). Propionate and butyrate concentrations were greater on WB than VF (p < .01); acetate concentrations were similar with both fibers. No correlation between NDF digestibility and SCFA concentrations was observed. Despite differences in origin, chemistry, particle size, and subject transit time, the WB and VF were similar in NDF fermentability. Molar ratios of specific SCFAs were influenced by type of fiber ingested.
Adult↗
Effects of cereal and vegetable fiber feeding on potential risk factors for colon cancer.
The effects of two doses of cereal fiber and vegetable fiber on mean transit time, stool weight, fecal pH and fecal bile acids were examined in 34 healthy volunteers. Subjects consumed five diets in random order for 23 days each, consisting of a fiber-free liquid diet and quick breads containing 0 g added dietary fiber, 10 g fiber as wheat bran (WB), 30 g fiber as WB, 10 g fiber as vegetable fiber (VF), and 30 g fiber as VF. Fecal wet and dry weights were 43% and 19% higher, respectively, on WB as compared to VF (P < 0.0001). Fecal pH was lower on WB than on VF (P < 0.0001) and decreased with increased fiber intake (P < 0.005). Transit time was 36% faster with WB than with VF (P < 0.0001). There was no VF dose effect on transit time, but transit time was 23% faster on 30 g WB than on 10 g WB (P = 0.04). Total bile acid concentrations decreased with increased fiber dose (P < 0.0001) but were not significantly different between WB and VF. Daily total bile acid excretion was 14% lower on VF compared to WB (P = 0.01). There was no VF dose effect on total bile acid excretion, but excretion was 13% lower on 30 g WB than on 10 g WB (P = 0.04). These findings are consistent with the capacity of fiber to alter potential risk factors for colon cancer but do not explain differences in epidemiological data between vegetable and cereal intake.
Adult↗
Dietary modulation of serum platelet-derived growth factor-AB levels.
Epidemiological studies have demonstrated that diets high in vegetables and fruit are associated with a decreased risk of cancer and, possibly cardiovascular disease. Certain constituents of vegetables and fruit inhibit the in vitro activity of platelet-derived growth factor (PDGF), a potent mitogen implicated in both cancer and cardiovascular disease. Few studies have measured PDGF in relationship to diet in vivo. Specifically, there are no data regarding the changes in PDGF levels of mitogenic activity after a dietary intervention. In this study, 19 young, healthy individuals consumed four (9-day) experimental diets in random order: (a) control diet alone; (b) control diet plus carotenoid-rich vegetables; (c) control diet plus cruciferous vegetables; and (d) control diet plus soy foods. Compared to the control diet, there was a significant elevation in PDGF-AB serum levels when the individuals were consuming the soy diet (P = 0.016). Increased PDGF-AB levels were also noted for the carotenoid diet. There was no change from baseline levels when individuals were consuming the cruciferous diet. Overall, mitogenic activity did not change on any of the experimental diets. This study suggests that high soy and carotenoid diets increase serum levels of PDGF-AB. This may represent an additional mechanism by which diet influences individual risk of cancer; further investigation into the role of diet and growth factors is warranted.
Cardiovascular Diseases↗
Plasma carotenoids as biomarkers of vegetable intake: the University of Minnesota Cancer Prevention Research Unit Feeding Studies.
High vegetable intake has been associated with a decreased risk for various human cancers in epidemiological studies. Carotenoids are plant compounds that may both possess chemopreventive activity and be useful biomarkers of vegetable and fruit intake. Nineteen men and women were randomized into a controlled cross-over feeding study to measure the effect of vegetable intake on plasma carotenoid concentrations. Participants consumed each of 4 experimental diets for 9 days. The control diet consisted of commonly consumed foods and was essentially carotenoid free. High vegetable diets (carotenoid, cruciferous, and soy) consisted of the control diet plus carrots and spinach (carotenoid), broccoli and cauliflower (cruciferous), and tofu and FriChik (soy). Plasma carotenoid concentrations were highest on the carotenoid and cruciferous diets. When compared to the control, mean plasma alpha-carotene, beta-carotene, and lutein concentrations were 5.2, 3.3 and 2.2 times higher on the carotenoid diet, respectively (P < 0.001). Mean plasma lutein concentrations were 2.1 times higher on the cruciferous versus the control diet (P < 0.001). There were no differences between diets in plasma beta-cryptoxanthin and lycopene concentrations. These data indicate that plasma alpha-carotene, beta-carotene, and lutein may be useful biomarkers of carotenoid-rich food intake and that lutein may act as an intake biomarker of commonly consumed vegetables in the Cruciferae family. These findings should prove useful in undertaking dietary intervention trials because they suggest the feasibility of monitoring intake of some plant foods and of distinguishing among plant food groups.
Adult↗