Low-fiber Meal Research Articles

Effect of Kithul Palm (Caryota urens) Fiber on Subjective Satiety and Food Intake of Normal and Overweight Women in Sri Lanka

Dietary fiber plays prominent role in satiety characteristics of meals. Kithul palm flour is a conventional food ingredient consumed in Sri Lanka, believed having superior satiety characteristics. This study aimed to find the subjective satiety characteristics of Kithul flour meal compared to soluble fiber meal (Psyllium) and low fiber meal. Three arm, single blinded, cross over placebo controlled study was designed with three isocaloric treatments (carbohydrate 55%, fat 30% and protein 15%) having same energy density (~1 kcal/g). Satiety characteristics after ingestion of treatment meal were recorded using Visual Analog Scale (VAS). The Kithul flour meal had significant reduction in hunger (P=0.0025), increment in fullness (P=0.0408), reduction in desire to eat (P<0.0001), and reduced prospective food consumption (P<0.0001) values compared to the Psyllium meal. Further, Kithul flour meal had increased fullness (P=0.0388), reduced desire to eat (P=0.0002), and reduced prospective food consumption (P<0.0001) compared to the low-fiber control meal. Kithul flour meal showed superior satiety results in overweight women compared to normal weight women.

Effects of Low-Fat and High-Fat Meals, with and without Dietary Fiber, on Postprandial Endothelial Function, Triglyceridemia, and Glycemia in Adolescents.

The consumption of fiber-rich foods may negate the deleterious effects of high-fat meals on postprandial triglyceridemia and endothelial function. Despite supportive data in adults, little is known about the effects of high-fat and high-fiber foods on cardiovascular health parameters in pediatric populations. In this crossover trial, male and female adolescents (n = 10; 14.1 + 2.6 years; range 10–17 years) consumed (1) low-fat, low-fiber, (2) low-fat, high-fiber, (3) high-fat, low-fiber, and (4) high-fat, high-fiber breakfast meals in randomized order, each following an overnight fast. Baseline and 4 h post-meal blood was obtained for determination of glucose, insulin and triglyceride concentrations. Endothelial function was assessed via brachial artery flow-mediated dilation (FMD). Postprandial FMD was not significantly changed after any meal. However, regression analyses revealed a significant inverse relationship between the change in 4 h triglyceride concentration and change in 4 h FMD for the high-fat, low-fiber meal (β = −0.087; 95% CI = −0.138 to −0.037; p = 0.001) that was no longer significant in the high-fat, high-fiber meal (β = −0.044; 95% CI = −0.117 to 0.029; p = 0.227). Interpretation of these analyses must be qualified by acknowledging that between-meal comparison revealed that the two regression lines were not statistically different (p = 0.226). Addition of high-fiber cereal to the high-fat meal also reduced 4 h postprandial triglyceride increases by ~50% (p = 0.056). A high-fiber breakfast cereal did not attenuate postprandial glucose and insulin responses after consumption of a low-fat meal. While further work is needed to confirm these results in larger cohorts, our findings indicate the potential importance of cereal fiber in blunting the inverse relationship between postprandial hypertriglyceridemia and FMD after consumption of a high-fat meal in adolescents.

Addition of Rye Bran and Pea Fiber to Pork Meatballs Enhances Subjective Satiety in Healthy Men, but Does Not Change Glycemic or Hormonal Responses: A Randomized Crossover Meal Test Study

Background: The development of high-protein, fiber-rich foods targeting appetite control could be an efficient tool in obesity prevention.Objectives: We investigated whether ad libitum energy intake (EI), appetite, and metabolic markers in a meal context were affected by 1) fiber addition (rye bran and pea fiber) to pork meatballs, 2) the food matrix of the fiber (fiber meatballs compared with fiber bread), or 3) the protein source (animal compared with vegetable protein patties).Methods: In a crossover design, 40 healthy men [mean ± SD: body mass index (BMI; in kg/m2), 22.2 ± 1.9; age, 23.3 ± 2.9 y] consumed 4 test meals: a low-fiber meal consisting of pork meatballs plus wheat bread (LF meal); pork meatballs plus fiber bread; fiber meatballs plus wheat bread, and vegetable patties with a natural fiber content plus wheat bread (∼3000 kJ; protein ∼18% of energy, carbohydrate ∼50% of energy, fat ∼30% of energy; 13 g fiber in the fiber meals). Ad libitum EI after 4 h was the primary endpoint. Moreover, appetite sensations and postprandial responses of glucose, insulin, glucagon-like peptide-1, peptide YY 3-36, and plasma amino acids were measured.Results: Ad libitum EI did not differ significantly between the meals. Satiety and fullness increased 11% and 13%, respectively, and hunger and prospective intake decreased 17% and 15%, respectively, after the meal of fiber meatballs plus wheat bread compared with the LF meal (P < 0.01). Hormonal and metabolic responses did not differ between the meals. In general, plasma amino acid concentrations were higher after the fiber-rich meals than after the LF meal.Conclusions: Meals based on meatballs and bread with differences in the fiber content, food matrix of fiber, and protein source had similar effects on ad libitum EI in healthy men. However, fiber addition to pork meatballs favorably affected appetite sensations but without changes in hormonal and metabolic responses. Moreover, animal- and vegetable-protein-based, fiber-matched meals had similar effects on appetite regulation. This trial was registered at clinicaltrials.gov as NCT02521805.

Glycemic and insulinemic responses are blunted by the consumption of a smoothie‐type beverage containing a whole‐grain fiber composite ingredient

This study assessed the effects of consuming a novel co‐processed composite ingredient comprised of a viscous fiber and whole‐grain high‐amylose maize flour, a rich source of resistant starch, on glycemic and insulinemic responses to meals. It was hypothesized that a smoothie‐type beverage containing the ingredient would blunt the post‐prandial responses in serum glucose and insulin concentrations compared to a beverage containing maltodextrin (MD). Nineteen healthy men and women (26 ± 3 years, BMI 24.3 ± 2.8 kg/m2) participated in 2 testing days (randomized crossover design) separated by at least 1 week. Subjects were counseled to consume a standard low‐fiber diet on each day prior to testing. On each testing day, blood samples were collected at baseline and incrementally for 8 hours after consuming a standardized low‐fiber meal with a beverage containing the composite ingredient or MD; a standard low‐fiber meal (without the composite ingredient or MD) was consumed 4 hours after the first meal. The composite ingredient blunted the post‐prandial glycemic (AUC0‐8h 3548 ± 1722 vs. 5352 ± 3564 mg/dL•480 min) and insulinemic (AUC0‐8h 7612 ± 3799 vs. 9769 ± 5156 µU/mL•480 min) responses (p&lt;0.05) versus MD. Glycemic and insulinemic responses were lowered by 53 and 78%, respectively, after the first meal and by 17 and 11% after the second meal (p&lt;0.05) with consumption of the composite ingredient. These findings support the use of this composite ingredient for insulin‐mediated glucose control.SupportIngredion Incorporated; NIH UL1TR001108; Purdue University

Die Gastroparese des kritisch kranken Patienten – ein unterschätztes Problem?

Intestinal motility disturbances - like gastroparesis - worsen the outcome of critically ill patients. Inadequate and delayed feeding as well as micro aspiration, pneumonia and systemic infections up to sepsis and multiple organ failure have to be mentioned. Especially in milder cases and in the beginning symptoms are unspecific and diffuse. On the other hand the awareness of physicians has not been raised sufficiently; both problems are responsible for a lower number of patients diagnosed than affected. Especially in critically ill patients it is reasonable to distinguish between a temporary and a permanent gastroparesis. In patients with permanent gastroparesis we distinguish between three grades of severity. The most important therapeutic option is to adapt enteral nutrition according to the delay in gastric emptying. Four to six fluid-dominated, low fat and low fiber meals should be preferred in patients who eat by themselves, in intubated patients enteral nutrition should be started with lower rates, and increased more slowly. Prokinetic and antiemetic drugs complete the therapeutic options we have in critically ill patients.

The acute effects of psyllium on postprandial lipaemia and thermogenesis in overweight and obese men

Overweight and obesity is one of the risk factors for developing CVD. At present, very little is known about the acute effects of dietary fibre on lipids, glucose and insulin, resting energy expenditure and diet-induced thermogenesis in overweight and obese individuals. This study examined the postprandial metabolic effects of dietary fibre in overweight and obese men. Ten overweight and obese men consumed a mixed meal accompanied by either a high-fibre or low-fibre supplement on two separate visits, in a random order, 1 week apart. Two isoenergetic breakfast meals with similar composition were consumed by ten overweight/obese men. The meals contained either a low (3 g) or high (15 g) amount of fibre, low-fibre meal (LFM) and high-fibre meal (HFM) respectively. Analysis was carried out using paired t test and ANOVA. Serum TAG incremental area under the curve during 6 h of the postprandial period was significantly lower after the consumption of HFM compared with LFM. At the first hour of the postprandial period, plasma apo B48 concentration after consumption of HFM was significantly lower compared with LFM. The resting energy expenditure and diet-induced thermogenesis after both meals was similar during 6 h of the postprandial period. Collectively, these findings suggest that a single acute dose of dietary fibre in the form of psyllium supplement can decrease arterial exposure to TAG and modify chylomicron responses in the postprandial period.

A High-Carbohydrate, High-Fiber Meal Improves Endothelial Function in Adults With the Metabolic Syndrome

Brachial artery flow-mediated dilation (FMD) using high-resolution ultrasound is a well-accepted, noninvasive bioassay for in vivo endothelium-generated nitric oxide (NO) in humans (1). Impaired NO generation characterizes the endothelial phenotype prone to the development of atherosclerosis and is linked to acute cardiovascular events. In several studies (2,3), endothelial dysfunction is an independent predictor of future cardiovascular morbidity and mortality. The postprandial state may be critical in the development of atherosclerosis (4). A single high-fat meal can induce endothelial dysfunction, whereas low-fat meals generally neither improve nor worsen FMD (5–8). The lack of a reported effect of low-fat meals on FMD may be attributable in part to insufficient dietary fiber in the meal. In particular, increased cereal fiber consumption is associated with reduced cardiovascular disease incidence and mortality (9–11) and lower prevalence of the metabolic syndrome (12) and may reduce systemic inflammation (13). We examined whether a high-carbohydrate meal, rich in cereal fiber, would improve brachial artery FMD in adults with the metabolic syndrome. For comparison, we also examined the impact of a low-carbohydrate, low-fiber meal. Twelve (9 women and 3 men: 44.7 ± 7.9 years of age, 98.9 ± 16.6 kg, 1.70 ± 0.07 m) nonsmoking, nondiabetic adults who met the International Diabetes Federation criteria for the metabolic syndrome participated in the study (14). Subjects were not taking medications to control blood lipids, blood …

Meal modulation of circulating interleukin 18 and adiponectin concentrations in healthy subjects and in patients with type 2 diabetes mellitus

A single high-fat meal induces endothelial activation, which is associated with increased serum concentrations of inflammatory cytokines. We compared the effect of 3 different meals on circulating concentrations of interleukin 8 (IL-8), interleukin 18 (IL-18), and adiponectin in healthy subjects and in patients with type 2 diabetes mellitus. Thirty patients with newly diagnosed type 2 diabetes and 30 matched, nondiabetic subjects received the following 3 isoenergetic (780 kcal) meals separated by 1-wk intervals: a high-fat meal; a high-carbohydrate, low-fiber (4.5 g) meal; and a high-carbohydrate, high-fiber meal in which refined-wheat flour was replaced with whole-wheat flour (16.8 g). We analyzed serum glucose and lipid variables and serum IL-8, IL-18, and adiponectin concentrations at baseline and at 2 and 4 h after ingestion of the meals. Compared with nondiabetic subjects, diabetic patients had higher fasting IL-8 (P < 0.05) and IL-18 (P < 0.01) concentrations and lower adiponectin concentrations (P < 0.01) at baseline. In both nondiabetic and diabetic subjects, IL-18 concentrations increased and adiponectin concentrations decreased (P < 0.05) from baseline concentrations after consumption of the high-fat meal. After consumption of the high-carbohydrate, high-fiber meal, serum IL-18 concentrations decreased from baseline concentrations (P < 0.05) in both nondiabetic and diabetic subjects; adiponectin concentrations decreased after the high-carbohydrate, low-fiber meal in diabetic patients. IL-8 concentrations did not change significantly after consumption of any of the 3 meals. This study provides evidence that circulating IL-18 and adiponectin concentrations are modulated by familiar foodstuffs in humans. Meal modulation of cytokines involved in atherogenesis may represent a safe strategy for ameliorating atherogenetic inflammatory activity in diabetic patients.

Plasma cholecystokinin is associated with subjective measures of satiety in women

Cholecystokinin is associated with satiety. Fat stimulates cholecystokinin release, and fiber appears to prolong cholecystokinin elevation during the alimentary period. We tested whether adding fiber or fat to a low-fat, low-fiber meal increases cholecystokinin release and enhances subjective measures of satiety and whether the cholecystokinin response correlates with subjective measures of satiety. Three isoenergetic breakfast meals were tested in a randomized crossover design: low fiber, low fat; high fiber, low fat; and low fiber, high fat. Blood samples were drawn from fasted subjects (7 men and 8 women) before and at different time points after test meal consumption for 6 h. Plasma was analyzed for cholecystokinin, insulin, glucose, and triacylglycerols. Visual analogue scales were used to assess subjects' hunger, desire to eat, fullness, and prospective consumption. In the women, the meals higher in fiber or in fat resulted in greater feelings of satiety and in significantly higher cholecystokinin responses than did the low-fat, low-fiber meal. In the men, the increase in cholecystokinin concentration did not differ between meals, but the 2 low-fat meals elicited a greater feeling of satiety than did the high-fat meal. The insulin response was significantly higher for the low-fiber, low-fat meal than for the other 2 meals, and the triacylglycerol response was greatest for the high-fat, low-fiber meal. In women, the feeling of satiety caused by cholecystokinin release is enhanced by increasing either the fiber or fat content of a low-fat, low-fiber meal.

MR colonography with barium-based fecal tagging: initial clinical experience.

To assess a strategy for fecal tagging with barium sulfate as an inexpensive tagging agent in conjunction with magnetic resonance (MR) colonography in patients suspected of having colorectal lesions. Twenty-four patients suspected of having colonic lesions because of rectal bleeding, positive fecal occult blood test results, or altered bowel habits underwent MR colonography and subsequent conventional colonoscopy. A 200-mL dose of a barium sulfate-containing contrast agent was ingested with each of four low-fiber meals, beginning 36 hours before the examination. For MR colonography, the colon was filled with tap water. Gadobenate dimeglumine was injected intravenously. Images were acquired 75 seconds after gadobenate dimeglumine administration by using only a T1-weighted three-dimensional gradient-echo sequence. Images were reviewed by two radiologists blinded to conventional colonoscopic data. By using colonoscopy as the reference standard, sensitivity and specificity of MR colonography were determined for detecting colorectal masses. On the basis of MR colonography, 15 polyps of 5-20 mm and 10 carcinomas were detected and later confirmed with conventional colonoscopy. Conventional colonoscopy depicted three additional lesions less than 8 mm in diameter. Thus, sensitivity of MR colonography was 89.3% (25 of 28) for lesions and 91.7% (22 of 24) for patients. Barium-tagged MR colonography obviates bowel cleansing and depicts all lesions exceeding 8 mm in diameter.

Beans, as a Source of Dietary Fiber, Increase Cholecystokinin and Apolipoprotein B48 Response to Test Meals in Men

Dry beans lower plasma cholesterol, an effect that has been associated with both the fiber and the protein content of beans. The objective of this study was to determine the acute hormone and lipid responses to a test meal that contained dry beans as a source of dietary fiber. A crossover design was employed in which men consumed the test meal and a control meal in random order. Both meals contained egg, bread, jelly, orange juice, milk and margarine. The high fiber meal contained white beans, whereas the low fiber (control) meal contained rice and dry milk. The men maintained their normal dietary pattern and fasted overnight before the study days. After a fasting blood sample was drawn, the men consumed the test meal and blood samples were collected over the next 6 h. Blood samples were analyzed for cholecystokinin (CCK), insulin and glucose. Plasma was separated into lipoprotein fractions and the triglyceride, cholesterol, apolipoprotein (apo) B100 and B48 content of triglyceride-rich lipoproteins determined. Insulin and glucose responses did not differ significantly between test meals; however, the CCK response was twice as high after the bean-containing meal than after the low fiber meal (P = 0.03). The increase in apo B48 concentration was significantly higher after the bean meal than after the low fiber meal (P < 0.05). Adding beans to a meal to increase fiber content prolongs the postprandial presence of intestinally derived lipoproteins and augments the CCK response to the meal.

Gastric Dysmotility and Gastroparesis.

Nutrition support in gastroparesis begins with encouraging smaller volume, low-fat, low-fiber meals and, if necessary, liquid caloric supplements. There should be a low threshold for placing a jejunal feeding tube either by laparoscopy or mini-laparotomy. Parenteral nutrition should be used only briefly during hospitalization and not encouraged or sustained as an outpatient. Metoclopramide is now the prokinetic of choice for patients who can tolerate this agent; subcutaneous administration is an important method that allows for continued guaranteed absorption. Low-dosage erythromycin also has a prokinetic role alone or in combination with metoclopramide. Domperidone, a centrally acting antiemetic and prokinetic, is only be available to US citizens who can access sources in Canada or Mexico. Antiemetics should be used extensively because nausea is a very severe debilitating symptom, which is under-appreciated and under-treated by physicians. We recommend scopolamine patches to gain maximal absorption, in spite of vomiting and unpredictable oral intakes. The 5-hydroxytryptamine-3 (5-HT3) antagonists ondansetron and granisetron are the most powerful agents. Relief bands using the P6 acupuncture point are useful adjunct. Special vigilance should be paid to situations that can undermine medical therapy or result in breakthrough symptoms, such as hyperglycemic events in patients with diabetes, migraine headaches, cyclic nausea and vomiting, menstrual cycles, rumination syndrome (psychogenic vomiting), and elevated herpes simplex titers. Most excitingly, the era of gastric electrical stimulation has arrived for patients not responding to standard medical therapy. The dramatic improvement in nausea and vomiting, as well as a sustained evidence of improved quality of life, gastric emptying, nutritional status, and decreased hospitalizations by this device are documented by long-term follow-up of more than a year for patients in this country and world-wide.

Postprandial lipid, glucose, insulin, and cholecystokinin responses in men fed barley pasta enriched with β-glucan

Fiber regulates the rate and site of lipid and carbohydrate digestion and absorption and thus can modify the alimentary responses to a meal. When fiber sources containing viscous polysaccharides are included in a meal, a slower rate of carbohydrate and lipid absorption will modify the alimentary hormone and lipid responses. We investigated in 11 healthy men the response of insulin, glucose, cholecystokinin, and lipid to 2 test meals containing beta-glucan. One of the meals was high in fiber (15.7 g) and the other meal was low in fiber (5.0 g). The low-fiber meal contained pasta made with wheat flour. The high-fiber meals contained pasta prepared by replacing 40% of the wheat with 2 types of barley flour: barley naturally high in beta-glucan and the other a flour enriched in beta-glucan during processing. Plasma glucose and insulin concentrations increased significantly after all meals but the insulin response was more blunted after the barley-containing meals. The test meals were low in fat (25% of energy) but elicited an increase in plasma triacylglycerol and cholecystokinin. Cholecystokinin remained elevated for a longer time after the barley-containing meals. After the low-fiber meal, plasma cholesterol concentrations did not change significantly; however, 4 h after the barley-containing meals, the cholesterol concentration dropped below the fasting concentration and was significantly lower than that after the low-fiber meal. Carbohydrate was more slowly absorbed from the 2 high-fiber meals. Consumption of the barley-containing meals appeared to stimulate reverse cholesterol transport, which may contribute to the cholesterol-lowering ability of barley.

Postprandial serum glucose, insulin, and lipoprotein responses to high- and low-fiber diets

The effects of high-fiber (HF) and low-fiber (LF) meals on postprandial serum glucose, insulin, lipid, lipoprotein, and apolipoprotein concentrations of 10 hypercholesterolemic men were examined using a random-order, cross over design. HF and LF meals provided 15% of energy as protein, 40% as carbohydrate, and 45% as fat, 200 mg cholesterol/1,000 kcal, and 25 g fiber/1,000 kcal for HF or 3 g fiber/1,000 kcal for LF. Responses over a 15-hour period after multiple meals (MM) and over a 10-hour period after a single meal (SM) were compared. HF meals were associated with a significant reduction in postprandial serum glucose ( P < .0005 after SM) and insulin ( P < .0005 afer SM). Serum free fatty acid (FFA) levels decreased significantly after MM and SM, but differences between HF and LF meals were insignificant. Although serum triglyceride responses did not differ significantly (ANOVA) between HF and LF meals, values were higher at 2 and 3 hours after a HF SM than after a LF SM and at 16 hours after HF MM than after LF MM. Although serum cholesterol values did not differ significantly (ANOVA) between HF and LF meals, values were higher after a HF SM than after a LF SM. Other subtle differences in responses of high-density lipoprotein (HDL) cholesterol, HDL2, and HDL3 concentrations were noted. These studies indicate that large increases in dietary fiber intake are accompanied by small changes in postprandial serum lipoprotein concentrations.

Gastric emptying of a solid meal is accelerated by the removal of dietary fibre naturally present in food.

Exogenous fibre added to liquid meals delays gastric emptying. Its effect on solid meals is uncertain, and nothing is known of the effect on gastric emptying of fibre naturally present in food. This study therefore looked at gastric emptying of two different solid meals in eight healthy subjects and their blood glucose responses. The meals were exactly equivalent except for the total dietary fibre content (high fibre 20 g, low fibre 4 g of dietary fibre per 1000 kcal) and supplied 870 kcal (700 kcal women), 47% of which was from carbohydrates, 36% from fats, and 17% from proteins. Ultrasonography was used to measure antral diameters before the meal (basal), immediately after it (time 0), and at 30, 60, 120, 180, 240, and 300 minutes. In addition, subjects filled in a questionnaire on their feelings of hunger, epigastric fullness, and satiety before the meal and at hourly intervals after it. Basal and maximal postprandial antral sections were similar for the two meals (basal section: 283.9 (29.5) v 340.9 (44.7) mm2 for the low and the high fibre meal, NS; maximal postprandial section: 1726 (101.9) v 1593 (120.4) mm2, NS). Total gastric emptying time was significantly reduced by fibre removal (186.0 (15.6) v 231.7 (17.3) minutes after the low and the high fibre meal, p < 0.05). Blood glucose was higher after the low fibre meal, and the area under the glycaemic curve significantly greater (226 (23.1) v 160 (20.0) mmol/min/dl-1, p < 0.05). No difference was found in satiety or fullness feelings, but hunger returned more rapidly after the low fibre meal. In conclusion, fibre naturally present in food delays gastric emptying of a solid meal, reduces the glycaemic response, and delays the return of hunger.

Decreased postprandial thermogenesis and fat oxidation but increased fullness after a high-fiber meal compared with a low-fiber meal

The effect of a high-fiber (4.7 g/MJ) and an isoenergetic low-fiber (1.7 g/MJ) meal on 6-h postprandial thermogenesis, substrate metabolism, hormones, and satiety was investigated in 10 healthy, normal-weight male subjects. Diet-induced thermogenesis (DIT) was significantly reduced after the high-fiber meal (416.4 +/- 28.6 kJ/6 h) compared with the low-fiber meal (498.5 +/- 23.1 kJ/6 h; ANOVA: P < 0.0001), as was postprandial fat oxidation (P < 0.0001). The difference in DIT was correlated with the different palatability of the test meal (r = 0.89, P < 0.01). No differences were observed in plasma concentrations of glucose, insulin, norepinephrine, epinephrine, or gastrointestinal hormones, but C-peptide increased less (P < 0.05) and nonesterified fatty acids decreased more (P < 0.05) after the high-fiber meal. Finally, fullness was increased and desire to eat decreased after the high-fiber meal (P < 0.0001). In conclusion, a high-fiber meal decreased DIT and fat oxidation but increased fullness compared with a low-fiber meal.

Calcium absorption in elderly subjects on high- and low-fiber diets: effect of gastric acidity

In vitro studies suggest that the effect of fiber in inhibiting calcium absorption is pH dependent. In nine normal, elderly control subjects and eight elderly subjects with achlorhydria, 47Ca was ingested with three test meals: a low-fiber meal (0.5 g dietary fiber), a high-fiber meal (10.5 g), and a high-fiber meal with 120 mL of 0.1 mol HC/L. In control subjects calcium retention, measured in a whole-body counter, was 25.7 +/- 4.0% (mean +/- SD) with the low-fiber meal, 19.1 +/- 1.9% with the high-fiber meal (P less than 0.002 vs low fiber), and 18.9 +/- 3.3% with the high-fiber-plus-acid meal (P less than 0.002 vs low fiber, NS vs high fiber). Calcium absorption in achlorhydric subjects was not different from control subjects: 26.2 +/- 8.0% with low fiber, 19.6 +/- 4.1% with high fiber (P less than 0.04 vs low fiber), and 21.0 +/- 5.8% with high fiber plus acid (P less than 0.04 vs low fiber, NS vs high fiber). We conclude that, in humans, the reduction in calcium absorption with high fiber intake is unaffected by gastric pH.

Dietary fiber and gender: effect on postprandial lipemia

The ability of guar gum and oat bran to alter postprandial lipemia and lipoprotein composition when added to a test meal (42% total calories as carbohydrate, 16% as protein, and 42% as fat) was examined in six males and six females who consumed both low- (0.4 g) and high- (15.4 g) fiber test meals on separate days. After an overnight fast participants consumed the test meal, and blood samples were obtained hourly for 8 h. Plasma glucose concentrations did not increase markedly after either meal in any of the subjects. In males, postprandial triglyceridemia was unaffected by fiber supplementation. In females, postprandial triglyceridemia was greater for the high- than for the low-fiber meal at 2, 3, and 4 h. After both meals triglyceridemia was higher in males than in females, which may be related to the lower ratio of high-density lipoprotein2 (HDL)2 to HDL3 in males vs females. Fiber supplementation and gender influence postprandial glycemia, lipemia, and lipoprotein composition.

Colonic carcinogenesis: the microbial feast or famine mechanism.

A mechanism is presented which suggests that high-fat, high-protein, low-fiber diets can cause an unfavorable microbial environment in the human colon which predisposes some individuals towards large bowel diseases. The digesta leaving the ileum on high-fat, high-protein, low-fiber diets has a high proportion of mucins, malabsorbed carbohydrates and proteins, bile acids, and sloughed epithelial cells. The irregular (pulsatile) emptying of rapidly fermentable ileal digesta into the colon causes a massive surge in microbial activity. The sudden availability of rapidly fermentable substrate generates a large microbial population in the exponential growth phase that soon depletes its substrate. For microorganisms to perpetuate until the next high-fat, high-protein, low-fiber meal propels ileal digesta into the colon, they must induce enzymes to ferment dying or dead microbes (cannibalism) in addition to colonic epithelial mucosa and mucins. As the carbohydrate-to-nitrogen ratio of the colonic contents decreases, the fermentation becomes more proteolytic and subacute levels of fermentation products such as ammonia may be generated. Carcinogens are concentrated within a small colonic mass and the probability of precancerous lesions and polyps developing in the colonic mucosa is directly related to the severity, frequency, and duration of these microbial "feast or famine" situations in the colon.

Effect of high- and low-fiber diets on plasma lipids and insulin

Seven healthy young adults were maintained for two separate 1-week periods on each of two very high-carbohydrate diets, one with low-fiber and one with high-fiber content. In both diets 15% of the calories were from protein, 15% from fat, and 70% were from carbohydrate. The low-fiber diet consisted of milk, glucose, and dextrins in liquid formula form, the high-fiber diet was composed of starchy foods. The crude fiber content of the high- and low-fiber diets was 18.0 and 1.0 g, respectively. The diets were isocaloric and the subjects maintained a stable weight. During the low-fiber diet the fasting triglycerides rose, reaching a peak 45% above base-line in 6 days. During the high-fiber diet the triglycerides fell to a level slightly below base-line. The cholesterol fell 16 and 23% below base-line on the low- and high-fiber diets. The glucose response to test meals representative of each diet was similar. The insulin response to a low-fiber meal was twice as great as that to a high-fiber meal containing an equivalent amount of carbohydrate. The results suggest that carbohydrate-induced hyperlipemia does not occur if the high carbohydrate diet is rich in dietary fiber, and furthermore that the insulin-stimulating potential of foods in a very high-carbohydrate diet is a critical determinant of the magnitude of carbohydrate-induced lipemia.