Dietary fiber and gastrointestinal function

Effects of Dietary Glycemic Index and Glycemic Load on Cardiometabolic and Reproductive Profiles in Women with Polycystic Ovary Syndrome: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Women with polycystic ovary syndrome (PCOS) exhibit cardiometabolic (e.g., insulin resistance) and associated reproductive disruptions. Lifestyle modification (e.g., diet) is recommended as the first-line therapy to manage PCOS; however, a favorable dietary regimen remains unclear beyond energy restriction. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to summarize evidence on impacts of dietary glycemic index (GI) or glycemic load (GL) on cardiometabolic and reproductive profiles to update the International Evidence-based Guideline for the Assessment and Management of PCOS. Databases of MEDLINE, Cochrane, Web of Science, and Scopus were searched through 30 October 2019, and confirmed on 25 March 2020, to identify RCTs (≥8 wk) comparing the effects of diets with lower (LGI/LGL) and higher (HGI/HGL) GI/GL on glucoregulatory outcomes, lipid profile, anthropometrics, and androgen status in PCOS. The primary outcome was HOMA-IR. Data were pooled by random-effects models and expressed as weighted mean differences and 95% CIs. The risk of bias was assessed by the Cochrane tool. Ten RCTs (n = 403) were eligible. Eight evaluated LGI and 2 LGL diets. LGI diets decreased HOMA-IR (-0.78; -1.20, -0.37; I2 = 86.6%), fasting insulin (-2.39; -4.78, 0.00 μIU/mL; I2 = 76.8%), total cholesterol (-11.13; -18.23, -4.04 mg/dL; I2 = 0.0%), LDL cholesterol (-6.27; -12.01, -0.53 mg/dL; I2 = 0.0%), triglycerides (-14.85; -28.75, -0.95 mg/dL; I2 = 31.0%), waist circumference (-2.81; -4.40, -1.23 cm; I2 = 53.9%), and total testosterone (-0.21; -0.32, -0.09 nmol/L; I2 = 8.6%) compared with HGI diets (all: P ≤ 0.05) without affecting fasting glucose, HDL cholesterol, weight, or free androgen index (all: P ≥ 0.07). Some results were contradictory and only described narratively for 2 RCTs that evaluated LGL diets, since inclusion in meta-analyses was not possible. LGI diets improved glucoregulatory outcomes (HOMA-IR, insulin), lipid profiles, abdominal adiposity, and androgen status, conceivably supporting their inclusion for dietary management of PCOS. Further RCTs should confirm these observations and address whether LGI diets improve more patient-pressing complications, including ovulatory cyclicity, infertility, and cardiovascular disease risk in this high-risk population. This review was registered at www.crd.york.ac.uk/PROSPERO as CRD42020175300.

Perioperative Heart-Brain Axis Protection in Obese Surgical Patients: The Nutrigenomic Approach

The number of obese patients undergoing cardiac and noncardiac surgery is rapidly increasing because they are more prone to concomitant diseases, such as diabetes, thrombosis, sleep-disordered breathing, cardiovascular and cerebrovascular disorders. Even if guidelines are already available to manage anesthesia and surgery of obese patients, the assessment of the perioperative morbidity and mortality from heart and brain disorders in morbidly obese surgical patients will be challenging in the next years. The present review will recapitulate the new mechanisms underlying the Heart-brain Axis (HBA) vulnerability during the perioperative period in healthy and morbidly obese patients. Finally, we will describe the nutrigenomics approach, an emerging noninvasive dietary tool, to maintain a healthy body weight and to minimize the HBA propensity to injury in obese individuals undergoing all types of surgery by personalized intake of plant compounds that may regulate the switch from health to disease in an epigenetic manner. Our review provides current insights into the mechanisms underlying HBA response in obese surgical patients and how they are modulated by epigenetically active food constituents.

Effects of Increasing Levels of Defatted Rice Bran on Intestinal Physical Barrier and Bacteria in Finishing Pigs

The aims of this study were to assess the effects of increasing levels of DFRB as a replacement for corns on intestinal physical barrier function and bacteria of finishing pigs. A total of 35 castrated finishing pigs (age: 158.5 ± 2.0 d, initial body weight: 62.9 ± 0.8 kg) were randomly divided into five dietary treatments (seven replicates/treatment) for a 28-day experimental period, i.e., a control diet with basal diet, and four experimental diets in which maize was replaced by 7%, 14%, 21%, and 28% DFRB, respectively. The results showed that serum endotoxins concentration and diamine oxidase (DAO) activity were both increased (linear, p = 0.0004, 0.001, respectively) with DFRB level. However, compared with control group, serum endotoxins concentration and DAO activity were not different in pigs fed with 7% DFRB in the diet. There was a quadratic response in serum D-lactate concentration to the increased DFRB (quadratic, p = 0.021). In the cecum, thickness of the intestinal wall significantly increased with increasing levels of DFRB in the diets (linear, p = 0.033), while crypt depth/thickness of the intestinal wall ratio significantly decreased with increasing level of DFRB in the diets (linear, p = 0.043). In the jejunum, total bacteria, Escherichia coli, and Bifidobacterium all responded quadratically to increasing levels of DFRB in the diets (quadratic, p = 0.003, 0.001, 0.006, respectively). Additionally, there was no difference in Escherichia coli in pigs fed 0%, 7%, and 14% DFRB diets. In the colon, there were quadratic responses in C. perfringens to the increased DFRB (quadratic, p = 0.023). C. perfringens reduced as the DFRB concentration increased from 0% to 14% and then increased. When D-lactate, total bacteria, Escherichia coli, Bifidobacterium, and C. perfringens were considered, the optimal substitution level of DFRB were 12.00%, 11.84%, 7.50%, 8.92%, and 15.92%, respectively. In conclusion, 7% DFRB had a beneficial effect on intestinal wall thickness, Bifidobacterium and C. perfringens, and had no adverse effect on intestinal permeability and Escherichia coli.

Using the Avocado to Test the Satiety Effects of a Fat-Fiber Combination in Place of Carbohydrate Energy in a Breakfast Meal in Overweight and Obese Men and Women: A Randomized Clinical Trial

This study aimed to investigate the satiety effects of isocalorically replacing carbohydrate energy in a meal with avocado-derived fats and fibers. In a randomized 3-arm, 6-h, crossover clinical trial, thirty-one overweight/obese adults consumed a low-fat control meal (CON, 76% carbohydrate, 14% fat as energy, 5 g fiber, ~640 kcal) or high-fat meals similar in total fat and energy, but increasing avocado-derived fat and fiber content from half (HA, 68 g; 51% carbohydrate, 40% fat as energy, 8.6 g fiber) or whole avocado (WA, 136 g; 50% carbohydrate, 43% fat as energy, 13.1 g fiber) on three separate occasions. Visual analog scales (VAS) assessed subjective satiety over 6 h. Hormones associated with satiety/appetite were measured in blood collected immediately after VAS. Stepwise multiple regression analysis was used to assess the relationship of VAS with hormones in WA and CON. Hunger suppression was enhanced after the WA compared to CON meal (p < 0.01). Subjects indicated feeling more satisfied after both HA and WA than CON (p < 0.05). Fullness was greater after CON and WA vs. HA (p < 0.005). PYY and GLP-1 were significantly elevated after WA vs. CON (p < 0.05), while insulin was significantly higher after CON vs. WA (p < 0.0001). Ghrelin was suppressed more by CON than WA (p < 0.05). Regression analysis indicated PYY was associated with subjective satiety after WA, whereas increased insulin predicted changes in subjective satiety after CON. Replacing carbohydrates in a high-carbohydrate meal with avocado-derived fat-fiber combination increased feelings of satiety mediated primarily by PYY vs. insulin. These findings may have important implications for addressing appetite management and metabolic concerns.

Effect of Bitter Melon Extracts on Lipid Levels in Japanese Subjects: A Randomized Controlled Study

Dyslipidemia is exemplified by high levels of low-density lipoprotein cholesterol (LDL-C) and represents a risk factor for cardiovascular diseases and requires therapeutic intervention. Several experimental studies suggest that bitter melon (Momordica charantia) improves lipid metabolism in animal models of dyslipidemia and diabetes. This study evaluated the effects of bitter melon extracts on lipid metabolism following a 30-day treatment period in Japanese adults. This randomized, double-blind, placebo-controlled trial included 43 adult volunteers who received either 100 mg of hot-water extracts of bitter melon (n = 23) or a placebo (n = 20) three times daily for 30 days. The body weight, blood pressure, and levels of LDL-C and other blood parameters of each subject were measured before and after the study period. The results showed that the intervention group exhibited significantly lower LDL-C levels (P = 0.02) as compared with the control group, and there were no significant changes in either group in terms of body weight, body mass index, systolic pressure, diastolic pressure, total cholesterol, high-density lipoprotein cholesterol, triglycerides, or blood glucose. These results suggested that bitter melon extracts might effectively lower LDL-C levels in humans and exhibit potential therapeutic value for the management of dyslipidemic conditions.

A Comparison of a Pulse-Based Diet and the Therapeutic Lifestyle Changes Diet in Combination with Exercise and Health Counselling on the Cardio-Metabolic Risk Profile in Women with Polycystic Ovary Syndrome: A Randomized Controlled Trial

We compared the effects of a low-glycemic index pulse-based diet, containing lentils, beans, split peas, and chickpeas, to the Therapeutic Lifestyle Changes (TLC) diet on cardio-metabolic measures in women with polycystic ovary syndrome (PCOS). Ninety-five women (18⁻35 years) enrolled in a 16-week intervention; 30 women in the pulse-based and 31 in the TLC groups completed the study. Women participated in aerobic exercise training (minimum 5 days/week for 45 min/day) and were counselled (monthly) about PCOS and lifestyle modification. Women underwent longitudinal follow-up post-intervention. The pulse-based group had a greater reduction in total area under the curve for insulin response to a 75-g oral glucose tolerance test (mean change ± SD: -121.0 ± 229.9 vs. -27.4 ± 110.2 µIU/mL × min; p = 0.05); diastolic blood pressure (-3.6 ± 6.7 vs. -0.2 ± 6.7 mmHg, p = 0.05); triglyceride (-0.2 ± 0.6 vs. 0.0 ± 0.5 mmol/L, p = 0.04); low-density lipoprotein cholesterol (-0.2 ± 0.4 vs. -0.1 ± 0.4 mmol/L, p = 0.05); total cholesterol/high-density lipoprotein cholesterol (TC/HDL-C; -0.4 ± 0.4 vs. 0.1 ± 0.4, p < 0.001); and a greater increase in HDL-C (0.1 ± 0.2 vs. -0.1 ± 0.2 mmol/L, p < 0.01) than the TLC group. Decreased TC/HDL-C (p = 0.02) at six-month and increased HDL-C and decreased TC/HDL-C (p ≤ 0.02) at 12-month post-intervention were maintained in the pulse-based group. A pulse-based diet may be more effective than the TLC diet at improving cardio-metabolic disease risk factors in women with PCOS.

TRIAL REGISTRATION

CinicalTrials.gov identifier, NCT01288638.

Long-term Intake of Pasta Containing Barley (1-3)Beta-D-Glucan Increases Neovascularization-mediated Cardioprotection through Endothelial Upregulation of Vascular Endothelial Growth Factor and Parkin

Barley (1-3)β-D-Glucan (BBG) enhances angiogenesis. Since pasta is very effective in providing a BBG-enriched diet, we hypothesized that the intake of pasta containing 3% BBG (P-BBG) induces neovascularization-mediated cardioprotection. Healthy adult male C57BL/6 mice fed P-BBG (n = 15) or wheat pasta (Control, n = 15) for five-weeks showed normal glucose tolerance and cardiac function. With a food intake similar to the Control, P-BBG mice showed a 109% survival rate (P < 0.01 vs. Control) after cardiac ischemia (30 min)/reperfusion (60 min) injury. Left ventricular (LV) anion superoxide production and infarct size in P-BBG mice were reduced by 62 and 35% (P < 0.0001 vs. Control), respectively. The capillary and arteriolar density of P-BBG hearts were respectively increased by 12 and 18% (P < 0.05 vs. Control). Compared to the Control group, the VEGF expression in P-BBG hearts was increased by 87.7% (P < 0.05); while, the p53 and Parkin expression was significantly increased by 125% and cleaved caspase-3 levels were reduced by 33% in P-BBG mice. In vitro, BBG was required to induce VEGF, p53 and Parkin expression in human umbelical vascular endothelial cells. Moreover, the BBG-induced Parkin expression was not affected by pifithrin-α (10 uM/7days), a p53 inhibitor. In conclusion, long-term dietary supplementation with P-BBG confers post-ischemic cardioprotection through endothelial upregulation of VEGF and Parkin.

Effects of β-Glucans Ingestion on Alveolar Bone Loss, Intestinal Morphology, Systemic Inflammatory Profile, and Pancreatic β-Cell Function in Rats with Periodontitis and Diabetes

This study aimed to evaluate the effects of β-glucan ingestion (Saccharomyces cerevisiae) on the plasmatic levels of tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10), alveolar bone loss, and pancreatic β-cell function (HOMA-BF) in diabetic rats with periodontal disease (PD). Besides, intestinal morphology was determined by the villus/crypt ratio. A total of 48 Wistar rats weighing 203 ± 18 g were used. Diabetes was induced by the intraperitoneal injection of streptozotocin (80 mg/kg) and periodontal inflammation, by ligature. The design was completely randomized in a factorial scheme 2 × 2 × 2 (diabetic or not, with or without periodontitis, and ingesting β-glucan or not). The animals received β-glucan by gavage for 28 days. Alveolar bone loss was determined by scanning electron microscopy (distance between the cementoenamel junction and alveolar bone crest) and histometric analysis (bone area between tooth roots). β-glucan reduced plasmatic levels of TNF-α in diabetic animals with PD and of IL-10 in animals with PD (p < 0.05). β-glucan reduced bone loss in animals with PD (p < 0.05). In diabetic animals, β-glucan improved β-cell function (p < 0.05). Diabetic animals had a higher villus/crypt ratio (p < 0.05). In conclusion, β-glucan ingestion reduced the systemic inflammatory profile, prevented alveolar bone loss, and improved β-cell function in diabetic animals with PD.

Effects of high β-glucan barley on visceral fat obesity in Japanese individuals: A randomized, double-blind study

OBJECTIVE

The aim of this study was to investigate whether a diet in which high β-glucan barley was substituted for rice would reduce visceral fat obesity in Japanese individuals.

METHODS

A randomized, double-blind, placebo-controlled intervention study was conducted with 100 Japanese individuals with waist circumference (WC) ≥85 cm for men or ≥90 cm for women and body mass index (BMI) ≥24 kg/m². Participants were randomly assigned to consume a mixture of rice and either high β-glucan barley (test group, 4.4 g/d) or β-glucan-free barley (placebo group) for 12 wk. Blood samples and computed tomography scans were obtained before and after the trial.

RESULTS

Both groups showed decreases in body weight and BMI, and these changes were significantly greater in the test group. WC and visceral fat area (VFA) significantly decreased in both groups (VFA: -10.7 cm² in the test group; -6.8 cm² in the placebo group). These changes did not differ significantly between the groups. However, a subgroup analysis of participants with VFA ≥100 cm² showed a significant decrease in the test group, and this decrease was significantly greater than in the placebo group.

CONCLUSIONS

The intake of high β-glucan barley led to significant and safe reductions in VFA, body weight, BMI, and WC in individuals with visceral fat obesity with VFA ≥100 cm². Barley high in β-glucan may contribute to preventing visceral fat obesity.

Role of polysaccharides in food, digestion, and health

Polysaccharides derived from plant foods are major components of the human diet, with limited contributions of related components from fungal and algal sources. In particular, starch and other storage carbohydrates are the major sources of energy in all diets, while cell wall polysaccharides are the major components of dietary fiber. We review the role of these components in the human diet, including their structure and distribution, their modification during food processing and effects on functional properties, their behavior in the gastrointestinal tract, and their contribution to healthy diets.

Dietary fiber intake and cardiometabolic risks among US adults, NHANES 1999-2010

BACKGROUND

Dietary fiber may decrease the risk of cardiovascular disease and associated risk factors. We examined trends in dietary fiber intake among diverse US adults between 1999 and 2010, and investigated associations between dietary fiber intake and cardiometabolic risks including metabolic syndrome, cardiovascular inflammation, and obesity.

METHODS

Our cross-sectional analysis included 23,168 men and nonpregnant women aged 20+ years from the 1999-2010 National Health and Nutrition Examination Survey. We used weighted multivariable logistic regression models to estimate predicted marginal risk ratios and 95% confidence intervals for the risks of having the metabolic syndrome, inflammation, and obesity associated with quintiles of dietary fiber intake.

RESULTS

Consistently, dietary fiber intake remained below recommended adequate intake levels for total fiber defined by the Institute of Medicine. Mean dietary fiber intake averaged 15.7-17.0 g. Mexican Americans (18.8 g) consumed more fiber than non-Hispanic whites (16.3 g) and non-Hispanic blacks (13.1 g). Comparing the highest with the lowest quintiles of dietary fiber intake, adjusted predicted marginal risk ratios (95% confidence interval) for the metabolic syndrome, inflammation, and obesity were 0.78 (0.69-0.88), 0.66 (0.61-0.72), and 0.77 (0.71-0.84), respectively. Dietary fiber was associated with lower levels of inflammation within each racial and ethnic group, although statistically significant associations between dietary fiber and either obesity or metabolic syndrome were seen only among whites.

CONCLUSIONS

Low dietary fiber intake from 1999-2010 in the US, and associations between higher dietary fiber and a lower prevalence of cardiometabolic risks suggest the need to develop new strategies and policies to increase dietary fiber intake.

Supplementation of the diet with the functional fiber PolyGlycoplex is well tolerated by healthy subjects in a clinical trial

Background

The relationship of dietary fiber to overall health is of great importance, as beneficial effects have been demonstrated with the use of fiber from diverse sources, some traditional, other novel. PolyGlycopleX^® (PGX^®) is a unique proprietary product composed of three water-soluble polysaccharides, that when processed using novel technology give rise to a final product – a soluble, highly viscous functional fiber.

Methods

Because of its potential use in food and dietary supplements, a randomized, double-blind, placebo controlled clinical study was conducted to evaluate the tolerance to PGX ingestion for 21 days, to a maximum dose level of 10 g per day, in healthy male and female volunteers. The main objective of the study was to evaluate the overall gastrointestinal (GI) tolerance, while secondary objectives were to evaluate possible changes in hematological, biochemical, urinary and fecal parameters.

Results

Results show that PGX is well tolerated as part of a regular diet with only mild to moderate adverse effects, similar to those seen with a moderate intake of dietary fiber in general, and fruits and vegetables. Because PGX is a highly viscous, functional fiber, it also demonstrates several physiological responses including, but not limited to maintaining healthy total and LDL cholesterol and uric acid levels.

The effects of inulin supplementation of diets with or without hydrolysed protein sources on digestibility, faecal characteristics, haematology and immunoglobulins in dogs

Dogs with food allergy are often treated by giving a diet with hydrolysed protein sources. Prebiotics might also be successful in prevention and treatment of allergic disease through their effect on the colonic microflora, analogous to studies on probiotics in allergic children. The present study was set up to investigate the effect of supplementing inulin (IN) to commercial hypoallergenic dog diets on apparent nutrient digestibility, faecal characteristics, haematology and Ig in dogs. Supplementation of 3 % IN did not affect faecal pH, food and water intake and urine production. Compared with the intact protein diet with a limited number of ingredients (L), the diet with a hydrolysed protein source (H) resulted in an increased water intake (P<0·001), which could be due to the osmotic effect of free amino acids. Faeces production was increased by IN due to increased faecal moisture content. Increased faeces production on the H diet was mainly due to a higher DM excretion. Subsequently, the apparent digestibility coefficient (ADC) of DM was lower in the H diet group. A similar result was noted for ADC of diethyl ether extract and crude ash. The ADC of crude protein was higher in the H diet group, whereas IN decreased the ADC of crude protein. Differences in the ADC of crude protein among the different diets disappeared after correction for a higher faecal biomass, except for the dogs fed the L + IN diet. Total faecal IgA concentrations were lower in the H group (P<0·05) because of lower antigenic stimulation of hydrolysed protein, which implies that hydrolysed protein is really hypoallergenic. The present study indicates that the use of hydrolysed protein diets for canine food allergy treatment can affect digestibility and that combination with IN affected apparent protein digestibility but not IgA response.

Effect of dietary supplementation with glucomannan on plasma total cholesterol and low density lipoprotein cholesterol in hypercholesterolemic children

AIM

This paper evaluates the effect of the adjunct of the hydrosoluble fiber glucomannan to a Step-One-Diet in 40 plasma hypercholesterolemic children, during a randomized controlled trial, to reduce plasma cholesterol.

METHODS

All the subjects recruited underwent an 8-week run in diet period; a Step-One-Diet was prescribed. After that, they were randomly allocated to one of two groups: Step-One-Diet only (control), and Step-One-Diet plus glucomannan in gelatine capsules. After another 8 weeks of treatment, the results were compared within and between the two groups.

RESULTS

Glucomannan treated group showed decreased values in plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) vs. control group after 8 weeks of treatment. The percentage decrease showed a statistically significant difference between sex groups. Decreases were observed in favor of female vs. male children in TC (24% vs. 9%) and LDL-C (30% vs. 9%).

CONCLUSIONS

These results suggest that glucomannan may represent a rationale adjunct to diet therapy in primary prevention in high risk hypercholesterolemic children.

Dietary supplementation with bean extract improves lipid profile in overweight and obese subjects

The aim of this study was to evaluate the long-term effects of a dietary supplementation of bean extract on serum lipids, nutritional parameters, and fat excretion in feces.Sixty-two overweight and obese (body mass index > 25 kg/m(2)) volunteers were randomized to receive the dietary supplement (n = 31, supplement group) or the placebo (n = 31, placebo group). There were 41 women and 21 men, ages 22 to 66 years. Two capsules of a dietary supplement or a placebo were administered three times daily for 3 mo. The supplement group was then invited to participate in an open-label study for 9 mo. Twenty-four subjects (7 men and 17 women) were randomized to receive two or four capsules of the supplement three times daily. Lipids and nutritional blood parameters were measured at baseline, after 3 mo, and at 12 mo. Excretion of fat in feces was measured. At 3 mo, reduction in serum concentration of cholesterol was found in the supplement group but not in the placebo group. High-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triacylglycerols in serum did not change in either group. In the 9-mo open-label study, no further reduction in serum cholesterol was observed. Low-density lipoprotein and the ratio of low- to high-density lipoprotein decreased, whereas triacylglycerols remained unchanged. Serum vitamin B12 and folic acid decreased but remained within the normal range. Ferritin and albumin in serum remained unchanged. No differences were observed in serum lipids and nutritional parameters between groups. The bean extract significantly increased fat excretion in feces. In conclusion, this dietary supplementation improved lipoprotein profile and enhanced fat excretion in feces in overweight and obese subjects.

Influence of impaired mastication on nutrition

It has been suggested that people who suffer from impaired masticatory function may adapt food consistency to their oral status (which may lead to deficient nutrient intake) or rely on the digestive system to compensate for the lack of oral preparation of food (which may increase the likelihood of digestive diseases and decrease gut absorption). Masticatory deficiency thus may be detrimental to health. This article reviews evidence of the effects of masticatory deficiency on nutrition. The selection of relevant literature was based on Medline queries using the following key words: mastication, nutrition, digestion, diet, and disease risk. Earlier work not listed in Medline but related to the subject also was reviewed. Only publications available in English were selected for inclusion. It is difficult to draw conclusions from many of the reviewed studies due to issues related to study design, confounding variables, and the subjective nature of the measurements. In particular, data supporting a link between masticatory function and deficient dietary intake often are based on relatively weak correlations and cannot confer a causal relationship.

Cholesterol-lowering effects of dietary fiber: a meta-analysis

BACKGROUND

The effects of dietary soluble fibers on blood cholesterol are uncertain.

OBJECTIVE

This meta-analysis of 67 controlled trials was performed to quantify the cholesterol-lowering effect of major dietary fibers.

DESIGN

Least-squares regression analyses were used to test the effect on blood lipids of pectin, oat bran, guar gum, and psyllium. Independent variables were type and amount of soluble fiber, initial cholesterol concentration, and other important study characteristics.

RESULTS

Soluble fiber, 2-10 g/d, was associated with small but significant decreases in total cholesterol [-0.045 mmol L(-1).g soluble fiber(-1) (95% CI: -0.054, -0.035)] and LDL cholesterol [-0.057 mmol.L(-1).g(-1) (95% CI: -0.070, -0.044)]. The effects on plasma lipids of soluble fiber from oat, psyllium, or pectin were not significantly different. We were unable to compare effects of guar because of the limited number of studies using 2-10 g/d. Triacylglycerols and HDL cholesterol were not significantly influenced by soluble fiber. Lipid changes were independent of study design, treatment length, and background dietary fat content.

CONCLUSIONS

Various soluble fibers reduce total and LDL cholesterol by similar amounts. The effect is small within the practical range of intake. For example, 3 g soluble fiber from oats (3 servings of oatmeal, 28 g each) can decrease total and LDL cholesterol by approximately 0.13 mmol/L. Increasing soluble fiber can make only a small contribution to dietary therapy to lower cholesterol.

Preparation of a dietary fiber mixture derived from different sources and its metabolic effects in rats

In this study we analyzed a commercial dietary fiber blend known as Fiber-Plus and a dietary fiber mixture (DFM) prepared in our lab (10% apple pectin, 10% orange pectin, 36% locust bean gum and 44% corncob composed of 56% fiber). DFM provided greater inhibition of starch digestion and glucose absorption (p < 0.05) than did Fiber-Plus. DFM was also found to be significantly more efficient (p < 0.05) than Fiber-Plus at reducing the glycemic response following starch loading. Rats fed DFM or corncob demonstrated a much lower glycemic response following a test meal as compared to those fed a fiber-free diet. Both fiber sources decreased fasting cholesterol and triglyceride concentrations; transit time was shortened and fecal values were higher than those of controls. beta-glucuronidase activity in intestinal segment contents and feces was lower in rats fed fiber. We conclude that DFM is effective in controlling plasma glucose and lipid levels. Corncob, a novel fiber source, could be beneficial in the treatment of gastrointestinal tract disorders and in the elimination of carcinogenic elements.