The effect of viscous soluble fiber on blood pressure: A systematic review and meta-analysis of randomized controlled trials.

AIMS: Dietary fiber intake, especially viscous soluble fiber, has been established as a means to reduce cardiometabolic risk factors. Whether this is true for blood pressure remains controversial. A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to investigate the effects of viscous soluble fiber supplementation on blood pressure and quantify the effect of individual fibers. DATA SYNTHESIS: MEDLINE, Embase, and Cochrane databases were searched. We included RCTs of ≥4-weeks in duration assessing viscous fiber supplementation from five types: ß-glucan from oats and barley, guar gum, konjac, pectin and psyllium, on systolic blood pressure (SBP) and diastolic blood pressure (DBP). Study data were pooled using the generic inverse variance method with random effects models and expressed as mean differences (MD) with 95% confidence intervals (CIs). Twenty-two (N = 1430) and twenty-one RCTs (N = 1343) were included in the final analysis for SBP and DBP, respectively. Viscous fiber reduced SBP (MD = -1.59 mmHg [95% CI: -2.72,-0.46]) and DBP (MD = -0.39 mmHg [95% CI: -0.76,-0.01]) at a median dose of 8.7 g/day (1.45-30 g/day) over a median follow-up of 7-weeks. Substantial heterogeneity in SBP (I2 = 72%, P < 0.01) and DBP (I2 = 67%, P < 0.01) analysis occurred. Within the five fiber types, SBP reductions were observed only for supplementation using psyllium fiber (MD = -2.39 mmHg [95% CI: -4.62,-0.17]). CONCLUSION: Viscous soluble fiber has an overall lowering effect on SBP and DBP. Inclusion of viscous fiber to habitual diets may have additional value in reducing CVD risk via improvement in blood pressure. PROTOCOL REGISTRATION: ClinicalTrials.gov identifier-NCT02670967.

Salba-chia (Salvia hispanica L.) in the treatment of overweight and obese patients with type 2 diabetes: A double-blind randomized controlled trial.

BACKGROUND AND AIM: Preliminary findings indicate that consumption of Salba-chia (Salvia hispanica L.), an ancient seed, improves management of type 2 diabetes and suppresses appetite. The aim of this study was to assesse the effect of Salba-chia on body weight, visceral obesity and obesity-related risk factors in overweight and obese adults with type 2 diabetes. METHODS: A double-blind, randomized, controlled trial with two parallel groups involved 77 overweight or obese patients with type 2 diabetes (HbA1c: 6.5-8.0%; BMI: 25-40 kg/m2). Both groups followed a 6-month calorie-restricted diet; one group received 30 g/1000 kcal/day of Salba-chia, the other 36 g/1000 kcal/day of an oat bran-based control. Primary endpoint was change in body weight over 6-months. Secondary endpoints included changes in waist circumference, body composition, glycemic control, C-reactive protein, and obesity-related satiety hormones. RESULTS: At 6-months, participants on Salba-chia had lost more weight than those on control (1.9 ± 0.5 kg and 0.3 ± 0.4 kg, respectively; P = 0.020), accompanied by a greater reduction in waist circumference (3.5 ± 0.7 cm and 1.1 ± 0.7 cm, respectively; P = 0.027). C-reactive protein was reduced by 1.1 ± 0.5 mg/L (39 ± 17%) on Salba-chia, compared to 0.2 ± 0.4 mg/L (7 ± 20%) on control (P = 0.045). Plasma adiponectin on the test intervention increased by 6.5 ± 0.7%, with no change observed on control (P = 0.022). CONCLUSIONS: The results of this study, support the beneficial role of Salba-chia seeds in promoting weight loss and improvements of obesity related risk factors, while maintaining good glycemic control. Supplementation of Salba-chia may be a useful dietary addition to conventional therapy in the management of obesity in diabetes. REGISTRATION: clinicaltrials.gov identifier: NCT01403571.

A six-month supplementation of mulberry, korean red ginseng, and banaba decreases biomarkers of systemic low-grade inflammation in subjects with impaired glucose tolerance and type 2 diabetes.

We sought the long-term efficacy of traditionally used antidiabetic herbs in controlling blood glucose homeostasis and low-grade inflammation. Ninety-four subjects with either impaired glucose tolerance or mild T2D were randomized either to treatment arm or placebo arm and received 1 : 1 : 1 mixture of ginseng roots, mulberry leaf water extract, and banaba leaf water extract (6 g/d) for 24 weeks. Oral 75 g glucose tolerance test was performed to measure glucose and insulin responses. Blood biomarkers of low-grade inflammation were also determined. Results found no significant difference in glucose homeostasis control measure changes. However, plasma intracellular adhesion molecule-1 (ICAM-1) concentration was decreased showing a significant between-treatment changes (P = 0.037). The concentrations of vascular cell adhesion molecule-1 (VCAM-1) (P = 0.014) and ICAM-1 (P = 0.048) were decreased in the treatment group at week 24, and the oxidized low-density lipoprotein (ox-LDL) concentration was reduced at week 24 compared to the baseline value in the treatment group (P = 0.003). These results indicate a long-term supplementation of ginseng, mulberry leaf, and banaba leaf suppresses inflammatory responses in T2D.

Viscosity of fiber preloads affects food intake in adolescents.

BACKGROUND AND AIMS: Dietary fiber that develops viscosity in the gastrointestinal tract is capable of addressing various aspects of food intake control. The aim of this study was to assess subsequent food intake and appetite in relation to the level of viscosity following three liquid preloads each containing 5 g of either a high (novel viscous polysaccharide; NVP), medium (glucomannan; GLM), or low (cellulose; CE) viscosity fiber. METHODS AND RESULTS: In this double-blind, randomized, controlled and crossover trial, 31 healthy weight adolescents (25 F:6 M; age 16.1+/-0.6 years; BMI 22.2+/-3.7 kg/m(2)) consumed one of the three preloads 90 min prior to an ad libitum pizza meal. Preloads were identical in taste, appearance, nutrient content and quantity of fiber, but different in their viscosities (10, 410, and 700 poise for CE, GLM, and NVP, respectively). Pizza intake was significantly lower (p=0.008) after consumption of the high-viscosity NVP (278+/-111 g) compared to the medium-viscosity GLM (313+/-123 g) and low-viscosity CE (316+/-138 g) preloads, with no difference between the GLM and CE preloads. Appetite scores, physical symptoms and 24-h intake did not differ among treatment groups. CONCLUSION: A highly viscous NVP preload leads to reduced subsequent food intake, in terms of both gram weight and calories, in healthy weight adolescents. This study provides preliminary evidence of an independent contribution of viscosity on food intake and may form a basis for further studies on factors influencing food intake in adolescents.

Comparison of flax (Linum usitatissimum) and Salba-chia (Salvia hispanica L.) seeds on postprandial glycemia and satiety in healthy individuals: a randomized, controlled, crossover study.

BACKGROUND/OBJECTIVES: Flax and Salba-chia seeds have risen in popularity owing to their favorable nutrient composition, including a high fiber content. Despite having comparable nutritional profiles, preliminary observations suggest differences in gelling properties, an attribute that may alter the kinetics of food digestion. Thus, we compared the effect of two seeds on postprandial glycemia and satiety scores. SUBJECTS/METHODS: Fifteen healthy participants (M/F: 5/10; age: 23.9±3 years; BMI: 22.2±0.8 kg/m2) were randomized to receive a 50 g glucose challenge, alone or supplemented with either 25 g ground Salba-chia or 31.5 g flax, on three separate occasions. Blood glucose samples and satiety ratings were collected at fasting and over 2-h postprandially. In addition, in vitro viscosity of the beverages was assessed utilizing standard rheological methodology. RESULTS: Both Salba-chia and flax reduced blood glucose area under the curve over 120 min by 82.5±19.7 mmol/l (P<0.001) and 60.0±19.7 mmol/l (P=0.014), respectively, relative to a glucose control. Salba-chia reduced peak glucose (-0.64±0.24 mmol/l; P=0.030) and increased time to peak (11.3±3.8 min; P=0.015) compared with flax. Salba-chia significantly reduced the mean ratings of desire to eat (-7±2 mm; P=0.005), prospective consumption (-7±2 mm; P=0.010) and overall appetite score (-6±2 mm; P=0.012), when compared with flax. The viscosity of Salba-chia, flax and control was 49.9, 2.5, and 0.002 Pa·s, respectively. CONCLUSIONS: Despite the similarities in nutritional composition, Salba-chia appears to have the ability to convert glucose into a slow-release carbohydrate and affect satiety to a greater extent than flax, possibly due to the higher fiber viscosity. Incorporation of either flax or Salba-chia into the diet may be beneficial, although use of Salba-chia may confer additional benefit.

A systematic review and meta-analysis of randomized controlled trials of the effect of barley ß-glucan on LDL-C, non-HDL-C and apoB for cardiovascular disease risk reductioni-iv.

BACKGROUND/OBJECTIVES: There has been recent interest in barley as a therapeutic food owing to its high content of beta-glucan (ß-glucan), a viscous soluble fiber recognized for its cholesterol-lowering properties. The objective of this study was to conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating the cholesterol-lowering potential of barley ß-glucan on low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C) and apolipoprotein B (apoB) for cardiovascular disease (CVD) risk reduction. METHODS: MEDLINE, Embase, CINAHL and the Cochrane CENTRAL were searched. We included RCTs of ⩾3-week duration assessing the effect of diets enriched with barley ß-glucan compared with controlled diets on LDL-C, non-HDL-C or apoB. Two independent reviewers extracted relevant data and assessed study quality and risk of bias. Data were pooled using the generic inverse-variance method with random effects models and expressed as mean differences (MDs) with 95% confidence intervals (CIs). Heterogeneity was assessed by the Cochran Q-statistic and quantified by the I2 statistic. RESULTS: Fourteen trials (N=615) were included in the final analysis. A median dose of 6.5 and 6.9 g/day of barley ß-glucan for a median duration of 4 weeks significantly reduced LDL-C (MD=-0.25 mmol/l (95% CI: -0.30, -0.20)) and non-HDL-C (MD=-0.31 mmol/l (95% CI: -0.39, -0.23)), respectively, with no significant changes to apoB levels, compared with control diets. There was evidence of considerable unexplained heterogeneity in the analysis of non-HDL-C (I2=98%). CONCLUSIONS: Pooled analyses show that barley ß-glucan has a lowering effect on LDL-C and non-HDL-C. Inclusion of barley-containing foods may be a strategy for achieving targets in CVD risk reduction.

The effect of ginseng (genus Panax) on blood pressure: a systematic review and meta-analysis of randomized controlled clinical trials.

Pre-clinical evidence indicates the potential for ginseng to reduce cardiovascular disease risk and acutely aid in blood pressure (BP) control. Clinical evidence evaluating repeated ginseng exposure, however, is controversial, triggering consumer and clinician concern. A systematic review and meta-analysis were conducted to assess whether ginseng has an effect on BP. MEDLINE, EMBASE, Cochrane and CINAHL were searched for relevant randomized controlled trials ⩾4 weeks that compared the effect of ginseng on systolic (SBP), diastolic (DBP) and/or mean arterial (MAP) BPs to control. Two independent reviewers extracted data and assessed methodological quality and risk of bias. Data were pooled using random-effects models and expressed as mean differences (MD) with 95% confidence intervals (CIs). Heterogeneity was assessed and quantified. Seventeen studies satisfied eligibility criteria (n=1381). No significant effect of ginseng on SBP, DBP and MAP was found. Stratified analysis, although not significant, appears to favour systolic BP improvement in diabetes, metabolic syndrome and obesity (MD=-2.76 mm Hg (95% CI=-6.40, 0.87); P=0.14). A priori subgroup analyses revealed significant association between body mass index and treatment differences (ß=-0.95 mm Hg (95% CI=-1.56, -0.34); P=0.007). Ginseng appears to have neutral vascular affects; therefore, should not be discouraged for concern of increased BP. More high-quality, randomized, controlled trials assessing BP as a primary end point, and use of standardized ginseng root or extracts are warranted to limit evidence of heterogeneity in ginseng research and to better understand its cardiovascular health potential.

Metabolic effects of reducing rate of glucose ingestion by single bolus versus continuous sipping.

Modifying the rate of absorption has been proposed as a therapeutic principle of specific relevance to diabetes. To demonstrate clearly the metabolic benefits that might result from reducing the rate of nutrient delivery, nine healthy volunteers took 50 g glucose in 700 ml water on two occasions: over 5-10 min (bolus) and at a constant rate over 3.5 h (sipping). Despite similar 4-h blood glucose areas, large reductions were seen in serum insulin (54 +/- 10%, P less than 0.001) and C-peptide (47 +/- 12%, P less than 0.01) areas after sipping, together with lower gastric inhibitory polypeptide and enteroglucagon levels and urinary catecholamine output. There was also prolonged suppression of plasma glucagon, growth hormone, and free-fatty acid (FFA) levels after sipping, whereas these levels rose 3-4 h after the glucose bolus. An intravenous glucose tolerance test at 4 h demonstrated a 48 +/- 10% (P less than 0.01) more rapid decline in blood glucose (Kg) after sipping than after the bolus. Furthermore, FFA and total branched-chain amino acid levels as additional markers of insulin action were lower over this period despite similar absolute levels of insulin and C-peptide. These findings indicate that prolonging the rate of glucose absorption enhances insulin economy and glucose disposal.

Effect of cocoa bran on low-density lipoprotein oxidation and fecal bulking.

BACKGROUND: Legumes have reported benefits in terms of reduced risk for coronary heart disease and of colonic health. A novel legume fiber, cocoa bran, also may have favorable health effects on serum lipid levels, low-density lipoprotein (LDL) cholesterol oxidation, and fecal bulk. METHODS: Twenty-five healthy normolipidemic subjects (13 men and 12 women) (mean +/- SEM age, 37 +/- 2 years; mean +/- SEM body mass index [calculated as weight in kilograms divided by the square of height in meters], 24.6 +/- 0.7) ate cocoa-bran and chocolate-flavored low-fiber breakfast cereals for 2-week periods, with 2-week washout, in a double-blind crossover study. The cocoa-bran cereal provided 25.0 g/d of total dietary fiber (TDF). The low-fiber cereal (5.6 g/d TDF) was of similar appearance and energy value. Fasting blood samples were obtained at the start and end of each period, and 4-day fecal collections were made from days 11 through 14. RESULTS: High-density lipoprotein (HDL) cholesterol level was higher (7.6% +/- 2.9%; P =.02) and the LDL/HDL cholesterol ratio was lower (6.7% +/- 2.3%; P =.007) for cocoa-bran compared with low-fiber cereal at 2 weeks. No effect was seen on LDL cholesterol oxidation. Mean fecal output was significantly higher for cocoa-bran than for low-fiber cereal (56 +/- 14 g/d; P<.001) and equal to the increase seen in the same subjects with wheat fiber in a previous study. CONCLUSIONS: A chocolate-flavored cocoa-bran cereal increased fecal bulk similarly to wheat bran and was associated with a reduction in the LDL/HDL cholesterol ratio. In view of the low-fat, high-fiber nature of the material, these results suggest a possible role for this novel fiber source in the diets of normal, hyperlipidemic, and constipated subjects.

American ginseng (Panax quinquefolius L) reduces postprandial glycemia in nondiabetic subjects and subjects with type 2 diabetes mellitus.

BACKGROUND: Despite a lack of medical evidence to support its therapeutic efficacy, the use of herbal medicine has increased considerably. Ginseng, one of the most widely used herbs, is hypothesized to play a role in carbohydrate metabolism and diabetes mellitus. We therefore undertook a preliminary short-term clinical study to assess whether American ginseng (Panax quinquefolius L) affects postprandial glycemia in humans. DESIGN: On 4 separate occasions, 10 nondiabetic subjects (mean [+/-SD] age, 34+/-7 years; mean [+/-SD] body mass index [BMI], 25.6 +/- 3 kg/m2) and 9 subjects with type 2 diabetes mellitus (mean [+/-SD] age, 62 +/- 7 years; mean [+/-SD] BMI, 29 +/- 5 kg/m2; mean [+/-SD] glycosylated hemoglobin A1c, 0.08+/-0.005) were randomized to receive 3-g ginseng or placebo capsules, either 40 minutes before or together with a 25-g oral glucose challenge. The placebo capsules contained com flour, in which the quantity of carbohydrate and appearance matched the ginseng capsules. A capillary blood sample was taken fasting and then at 15, 30, 45, 60, 90, and 120 (only for subjects with type 2 diabetes mellitus ) minutes after the glucose challenge. RESULTS: In nondiabetic subjects, no differences were found in postprandial glycemia between placebo and ginseng when administered together with the glucose challenge. When ginseng was taken 40 minutes before the glucose challenge, significant reductions were observed (P<.05). In subjects with type 2 diabetes mellitus, the same was true whether capsules were taken before or together with the glucose challenge (P<.05). Reductions in area under the glycemic curve were 18%+/-31% for nondiabetic subjects and 19+/-22% and 22+/-17% for subjects with type 2 diabetes mellitus administered before or together with the glucose challenge, respectively. CONCLUSIONS: American ginseng attenuated postprandial glycemia in both study groups. For nondiabetic subjects, to prevent unintended hypoglycemia it may be important that the American ginseng be taken with the meal.

Effect of meal dilution on the postprandial glycemic response. Implications for glycemic testing.

OBJECTIVE: To investigate the effect of varying the volume of sugar meals on the post-prandial glycemic response (PGR). RESEARCH DESIGN AND METHODS: On six separate occasions, after an overnight fast, blood glucose concentrations were measured in eight healthy subjects (34 +/- 4 years of age, BMI 22.9 +/- 0.9 kg/m2) after the consumption of 25 g glucose, sucrose, or fructose dissolved in either 200 or 600 ml of water. Blood was obtained at fasting and then at times 15, 30, 45, 60, and 90 min after the start of the test meal. RESULTS: PGR was found to be influenced by carbohydrate type (P < 0.001). Mean response areas (min.mmol.l-1) to the three sugars were statistically different (P < 0.05). Glucose had the highest response area (90.0 +/- 8.1), followed by sucrose (61.3 +/- 5.0) and then fructose (14.7 +/- 2.8). Independent of this effect, PGR was also found to be influenced by volume dose (P < 0.01). By tripling meal volume from 200 to 600 ml, PGR areas were significantly increased for all three sugars, glucose (79.3 +/- 10.3 vs. 100.8 +/- 12.0, P = 0.035), sucrose (52.6 +/- 5.5 vs. 70 +/- 7.4, P = 0.0094), and fructose (11.0 +/- 3.8 vs. 18.4 +/- 3.9, P = 0.012). Where the effects of time (P < 0.05) and dose (P < 0.05) were determined to be independent (interaction nonsignificant) for all three sugars, this increase in volume also significantly increased glycemic concentrations at 15 min, for glucose (P = 0.033) and sucrose (P = 0.026), suggesting that changes in gastric emptying time may be a mechanism of action. CONCLUSIONS: Varying the volume of liquid sugar meals alters PGR. Understanding this concept may help to reduce variability both in the glycemic testing of foods and oral glucose tolerance testing.

Similar postprandial glycemic reductions with escalation of dose and administration time of American ginseng in type 2 diabetes.

OBJECTIVE: We previously demonstrated that 3 g American ginseng (AG) reduced postprandial glycemia (PPG) in type 2 diabetic individuals. We investigated whether further reductions can be achieved with escalation of dose and time of AG administration. RESEARCH DESIGN AND METHODS: Ten type 2 diabetic patients (6 men, 4 women; age 63+/-2 years; BMI 27.7+/-1.5 kg/m2; HbA1c 7.3+/-0.3%) were randomly administered 0 g (placebo) or 3, 6, or 9 g ground AG root in capsules at 120, 80, 40, or 0 min before a 25-g oral glucose challenge. Capillary blood glucose was measured before ingestion of AG or placebo and at 0, 15, 30, 45, 60, 90, and 120 min from the start of the glucose challenge. RESULTS: Two-way analysis of variance (ANOVA) demonstrated that treatment (0, 3, 6, and 9 g AG) but not time of administration (120, 80, 40, or 0 min before the challenge) significantly affected PPG (P<0.05), with significant (P = 0.037) interaction for area under the curve (AUC). Pairwise comparisons showed that compared with 0 g (placebo), 3, 6, or 9 g significantly (P<0.05) reduced AUC (19.7, 15.3, and 15.9%, respectively) and incremental glycemia at 30 min (16.3, 18.4, and 18.4%, respectively), 45 min (12.5, 14.3, and 14.3%, respectively), and 120 min (59.1, 40.9, and 45.5%, respectively). However, pairwise comparisons showed no differences between the 3-, 6-, or 9-g doses and any of the times of administration. CONCLUSIONS: AG reduced PPG irrespective of dose and time of administration. No more than 3 g AG was required at any time in relation to the challenge to achieve reductions. Because these reductions included glycemia at the 2-h diagnostic end point, there may be implications for diabetes diagnosis and treatment.

Beneficial effect of low-glycemic index diet in overweight NIDDM subjects.

OBJECTIVE: To determine whether low-glycemic index (GI) diets have clinical utility in overweight patients with non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS: Six patients with NIDDM were studied on both high- and low-GI diets of 6-wk duration with metabolic diets with a randomized crossover design. Both diets were of similar composition (57% carbohydrate, 23% fat, and 34 g/day dietary fiber), but the low-GI diet had a GI of 58 compared with 86 for the high-GI diet. RESULTS: Small and similar amounts of weight were lost on both diets: 2.5 kg on high-GI diet and 1.8 kg on low-GI diet. On the low-GI diet, the mean level of serum fructosamine, as an index of overall blood glucose control, was lower than on the high-GI diet by 8% (P less than 0.05), and total serum cholesterol was lower by 7% (P less than 0.01). CONCLUSIONS: In overweight patients with NIDDM, reducing diet GI improves overall blood glucose and lipid control.

Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial.

OBJECTIVE: To examine whether Konjac-mannan (KJM) fiber improves metabolic control as measured by glycemia, lipidemia, and blood pressure in high-risk type 2 diabetic patients. RESEARCH DESIGN AND METHODS: A total of 11 hyperlipidemic and hypertensive type 2 diabetic patients treated conventionally by a low-fat diet and drug therapy participated. After an 8-week baseline, all were randomly assigned to take either KJM fiber-enriched test biscuits (0.7 g/412 kJ [100 kcal] of glucomannan) or matched placebo wheat bran fiber biscuits during two 3-week treatment phases separated by a 2-week washout period. The diet in either case was metabolically controlled and conformed to National Cholesterol Education Program Step 2 guidelines, while medications were maintained constant. Efficacy measures included serum fructosamine, lipid profiles, apolipoproteins, blood pressure, body weight, and nutritional analysis. RESULTS: Compared with placebo, KJM significantly reduced the metabolic control primary end points: serum fructosamine (5.7%, P = 0.007, adjusted alpha = 0.0167), total:HDL cholesterol ratio (10%, P = 0.03, adjusted alpha = 0.05), and systolic blood pressure (sBP) (6.9%, P = 0.02, adjusted alpha = 0.025). Secondary end points, including body weight, total, LDL, and HDL cholesterol, triglycerides, apolipoproteins A-1, B, and their ratio, glucose, insulin, and diastolic blood pressure, were not significant after adjustment by the Bonferroni-Hochberg procedure. CONCLUSIONS: KJM fiber added to conventional treatment may ameliorate glycemic control, blood lipid profile, and sBP in high-risk diabetic individuals, possibly improving the effectiveness of conventional treatment in type 2 diabetes.

Glycemic index of foods in individual subjects.

We studied 12 subjects with diabetes to determine how well the glycemic index (GI) predicted the ranking of glycemic responses of different foods in individuals. All subjects ate three mixed meals (bread, rice, or spaghetti with GIs of 100, 79, and 61, respectively) four times in a randomized complete block design. The mean glycemic response areas of the different meals ranked according to the predicted GI in every individual. The observed mean +/- SD GI values of the meals were significantly different from each other (bread 100 +/- 7, rice 75 +/- 9, spaghetti 54 +/- 9), with no significant difference in response between subjects. It is concluded that individuals share common mean GI values for different foods. Within confidence limits determined by the variability of glycemic responses, the number of repeated tests conducted, and the expected GI difference, the GI can be used to predict the ranking of the mean glycemic responses of mixed meals taken by individuals.

Beneficial effects of viscous dietary fiber from Konjac-mannan in subjects with the insulin resistance syndrome: results of a controlled metabolic trial.

OBJECTIVE: Dietary fiber has recently received recognition for reducing the risk of developing diabetes and heart disease. The implication is that it may have therapeutic benefit in prediabetic metabolic conditions. To test this hypothesis, we investigated the effect of supplementing a high-carbohydrate diet with fiber from Konjac-mannan (KJM) on metabolic control in subjects with the insulin resistance syndrome. RESEARCH DESIGN AND METHODS: We screened 278 free-living subjects between the ages of 45 and 65 years from the Canadian-Maltese Diabetes Study. A total of 11 (age 55+/-4 years, BMI 28+/-1.5 kg/m2) were recruited who satisfied the inclusion criteria: impaired glucose tolerance, reduced HDL cholesterol, elevated serum triglycerides, and moderate hypertension. After an 8-week baseline, they were randomly assigned to take either KJM fiber-enriched test biscuits (0.5 g of glucomannan per 100 kcal of dietary intake or 8-13 g/day) or wheat bran fiber (WB) control biscuits for two 3-week treatment periods separated by a 2-week washout. The diets were isoenergetic, metabolically controlled, and conformed to National Cholesterol Education Program Step 2 guidelines. Serum lipids, glycemic control, and blood pressure were the outcome measures. RESULTS: Decreases in serum cholesterol (total, 12.4+/-3.1%, P<0.004; LDL, 22+/-3.9%, P<0.002; total/HDL ratio, 15.2+/-3.4%, P<0.003; and LDL/HDL ratio, 22.2+/-4.1%, P< 0.002), apolipoprotein (apo) B (15.1+/-4.3%, P<0.0004), apo B/A-1 ratio (13.1+/-3.4%, P< 0.0003), and serum fructosamine (5.2+/-1.4%, P<0.002) were observed during KJM treatment compared with WB-control. Fasting blood glucose, insulin, triglycerides, HDL cholesterol, and body weight remained unchanged. CONCLUSIONS: A diet rich in high-viscosity KJM improves glycemic control and lipid profile, suggesting a therapeutic potential in the treatment of the insulin resistance syndrome.

Simple skinfold-thickness measurements complement conventional anthropometric assessments in predicting glucose tolerance.

BACKGROUND: Skinfold-thickness measurements are considered to have limited clinical utility. OBJECTIVE: To assess whether skinfold-thickness measurements may be a useful adjunct to conventional anthropometric assessments in predicting glucose and insulin regulation, we studied responses to replicate 75-g oral-glucose-tolerance tests (OGTTs) and performed simple anthropometry in a cross section of subjects. DESIGN: Thirty-five subjects completed the study: 11 lean [mean (+/-SEM) age: 33 +/- 3.2 y; body mass index (BMI; in kg/m(2)): 24.1 +/- 0.8; and percentage body fat (%BF): 11.5 +/- 1.5%], 12 normal-weight (age: 33 +/- 2.9 y; BMI: 23.9 +/- 0.7; and %BF: 24.3.5 +/- 1.3%), and 12 obese (age: 41 +/- 4.5 y; BMI: 34.5 +/- 1.7; and %BF: 34.2 +/- 1.5%) individuals. The lean and normal-weight groups were selected to have similar BMIs but different %BFs. We measured the participants' heights, weights, %BFs, waist circumferences, hip circumferences, and truncal and peripheral skinfold thicknesses. Subjects received nine 75-g OGTTs and blood samples were collected at 0, 15, 30, 45, 60, 90, and 120 min. Mean plasma glucose and insulin values were used to calculate the insulin sensitivity index. RESULTS: The obese group had higher plasma glucose concentrations and areas under the curve (AUCs) than did the normal-weight or lean group and higher plasma insulin concentrations and AUCs than did the lean group (P < 0.05). Stepwise multiple regression, with adjustment for demographic and anthropometric measurements, identified the following predictors: waist circumference, peripheral skinfold thickness, and BMI for fasting plasma glucose (partial R(2) = 0.20, 0.13, and 0.13, P < 0.05); waist circumference and truncal skinfold thickness for plasma glucose AUC (partial R(2) = 0.20 and 0.13, P < 0.05); age, waist-to-hip ratio, and peripheral skinfold thickness for fasting plasma insulin (partial R(2) = 0.26, 0.22, and 0.15, P < 0.05); truncal skinfold thickness for plasma insulin AUC (partial R(2) = 0.41, P < 0.001); and peripheral skinfold thickness for both 2-h plasma glucose (partial R(2) = 0.59, P < 0.001) and the insulin sensitivity index (partial R(2) = 0.49, P < 0.001). CONCLUSION: Skinfold-thickness measurements may complement other established measurements for predicting abnormal glucose and insulin regulation.

Low glycemic index: lente carbohydrates and physiological effects of altered food frequency.

Many factors influence carbohydrate absorption. Slower rates of absorption may have advantages in reducing postprandial glycemia and insulinemia and, in time, reduce serum low-density-lipoprotein (LDL) cholesterol and apolipoprotein B concentrations. Foods high in viscous fiber or antinutrients, or foods that are resistant to gelatinization, show slower rates of digestion and absorption and may be called low glycemic index or lente carbohydrate foods. Specific enzyme inhibitors may also cause lente effects. Certain small-intestinal effects of lente carbohydrate may be mimicked by altering feeding frequency (eg, nibbling vs gorging). Increased meal frequency reduces post-prandial insulin and glucose responses in people with non-insulin-dependent diabetes and in nondiabetic volunteers and lowers serum concentrations of LDL cholesterol and apolipoprotein B. Reduced hepatic cholesterol synthesis has been reported. Increased meal frequency may also slow small-intestinal absorption in the treatment of conditions such as diabetes, hyperlipidemia, and possibly obesity.

Specific types of colonic fermentation may raise low-density-lipoprotein-cholesterol concentrations.

To assess the effects of increased colonic fermentation on serum lipids, eight healthy volunteers were placed on two identical 2-wk metabolic diets, one of which was supplemented with lactulose (18-25 g/d). Lactulose raised day-long concentrations of breath hydrogen and serum glutamine as indicators of increased colonic fermentation by 78 +/- 13% (P less than 0.001) and 24.7 +/- 9.5% (P less than 0.05), respectively). Unexpectedly, however, fasting serum total and low-density-lipoprotein cholesterol and apolipoprotein B concentrations were higher at 2 wk by 8.9 +/- 1.5% (P less than 0.001), 10.9 +/- 2.2% (P less than 0.005), and 18.9 +/- 5.9% (P less than 0.02), respectively, compared with the control diet. With lactulose, mean free fatty acid concentrations were reduced over the day by 19.5 +/- 5.9% (P less than 0.02), with no change in mean day-long blood glucose, serum insulin, or C-peptide concentrations. We conclude that certain rapidly fermented substrates may raise rather than lower serum lipids, possibly through increasing the amount of acetate absorbed from the colon.

Metabolic advantages of spreading the nutrient load: effects of increased meal frequency in non-insulin-dependent diabetes.

The acute effect of increasing meal frequency as a model of slow absorption was studied for 1 d in 11 patients with non-insulin-dependent diabetes. On 1 d they took 13 snacks (the nibbling diet) and on another day the same diet was taken as three meals and one snack (the three-meal diet). The nibbling diet reduced mean blood glucose, serum insulin, and C peptide concentrations over the 9.5 h of observation and 24-h urinary C peptide output by 12.7 +/- 3.7% (mean +/- SE) (P = 0.0062), 20.1 +/- 5.8% (P = 0.0108), 9.2 +/- 2.6% (P = 0.0073), and 20.37 +/- 8.12% (P = 0.039), respectively, compared with the three-meal diet. Serum triglyceride concentrations were lower by 8.5 +/- 3.2% (P = 0.037). Despite lower insulin concentrations on the nibbling diet, the concentrations of free fatty acids, 3-hydroxybutyrate, and the insulin-sensitive branched-chain amino acids responded similarly on both treatments. Metabolic benefits seen with increased meal frequency may explain the success of similar agents that prolong absorption, including fiber and enzyme inhibitors.