Post-prandial responses to cereal products enriched with barley beta-glucan

Meta-analysis of the effect of β-glucan intake on blood cholesterol and glucose levels

OBJECTIVE

A meta-analysis was performed on epidemiologic studies to assess the relation between β-glucan consumption from oats and from barley on blood cholesterol level, triglyceride/triacylglycerol (TGL/TAG) level, and blood glucose level (BGL) in humans. In addition, the effect of β-glucan on total cholesterol (TC) and BGL was translated into an empirical dose-response model.

METHODS

Thirty research articles that evaluated the effect of different exposure levels of β-glucan on blood cholesterol and BGL were analyzed, yielding 126 clinical studies.

RESULTS

There was a significant inverse relation in TC (-0.60 mmol/L, 95% confidence interval [CI] -0.85 to -0.34), low-density lipoprotein (-0.66 mmol/L, 95% CI -0.96 to -0.36), and TGL/TAG (-0.04 mmol/L, 95% CI -0.15 to 0.07) after consumption of β-glucan. In contrast, an increase in high-density lipoprotein cholesterol was noted (0.03 mmol/L, 95% CI -0.06 to 0.13) with the random-effect model. The analysis showed a significant change in BGL (-2.58 mmol/L, 95% CI -3.22 to -1.84) with high heterogeneity between (I(2) = 97%) and across (τ(2) = 5.88) the studies. The fixed-effect model showed a significant change in TC, low-density lipoprotein, and BGL, whereas it showed no significant changes in high-density lipoprotein and TGL/TAG. The dose-response model showed that a 3-g/d dose of oat or barley β-glucan was sufficient to decrease TC.

CONCLUSION

Consumption of 3 g/d of oat or barley β-glucan is sufficient to decrease blood cholesterol, whereas the effect on BGL is still inconclusive, with high heterogeneity, and requires further clinical research studies with longer intervention periods.

Consumption of barley beta-glucan ameliorates fatty liver and insulin resistance in mice fed a high-fat diet

Consumption of a diet high in barley beta-glucan (BG) has been shown to prevent insulin resistance. To investigate the mechanism for the effects of barley BG, three groups of male 7-wk-old C57BL/6J mice were fed high-fat diets containing 0, 2, or 4% of barley BG for 12 wk. The 2% BG and 4% BG groups had significantly lower body weights compared with the 0% BG group. The 4% BG group demonstrated improved glucose tolerance and lower levels of insulin-resistance index and glucose-dependent insulinotropic polypeptide. Consumption of the BG diet decreased hepatic lipid content. Mice on the BG diet also demonstrated decreased fatty acid synthase and increased cholesterol 7alpha-hydroxylase gene expression levels. The BG diet promoted hepatic insulin signaling by decreasing serine phosphorylation of insulin receptor substrate 1 and activating Akt, and it decreased mRNA levels of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. In summary, consumption of BG reduced weight gain, decreased hepatic lipid accumulation, and improved insulin sensitivity in mice fed a high-fat diet. Insulin signaling enhanced due to the expression changes of glucose and lipid metabolism genes by BG consumption. Consumption of barley BG could be an effective strategy for preventing obesity, insulin resistance, and the metabolic syndrome.

Effect of adding the novel fiber, PGX®, to commonly consumed foods on glycemic response, glycemic index and GRIP: a simple and effective strategy for reducing post prandial blood glucose levels--a randomized, controlled trial

BACKGROUND

Reductions in postprandial glycemia have been demonstrated previously with the addition of the novel viscous polysaccharide (NVP), PolyGlycopleX® (PGX®), to an OGTT or white bread. This study explores whether these reductions are sustained when NVP is added to a range of commonly consumed foods or incorporated into a breakfast cereal.

METHODS

Ten healthy subjects (4M, 6F; age 37.3 ± 3.6 y; BMI 23.8 ± 1.3 kg/m2), participated in an acute, randomized controlled trial. The glycemic response to cornflakes, rice, yogurt, and a frozen dinner with and without 5 g of NVP sprinkled onto the food was determined. In addition, 3 granolas with different levels of NVP and 3 control white breads and one white bread and milk were also consumed. All meals contained 50 g of available carbohydrate. Capillary blood samples were taken fasting and at 15, 30, 45, 60, 90 and 120 min after the start of the meal. The glycemic index (GI) and the glycemic reduction index potential (GRIP) were calculated. The blood glucose concentrations at each time and the iAUC values were subjected to repeated-measures analysis of variance (ANOVA) examining for the effect of test meal. After demonstration of significant heterogeneity, differences between individual means was assessed using GLM ANOVA with Tukey test to adjust for multiple comparisons.

RESULTS

Addition of NVP reduced blood glucose response irrespective of food or dose (p < 0.01). The GI of cornflakes, cornflakes+NVP, rice, rice+NVP, yogurt, yogurt+NVP, turkey dinner, and turkey dinner+NVP were 83 ± 8, 58 ± 7, 82 ± 8, 45 ± 4, 44 ± 4, 38 ± 3, 55 ± 5 and 41 ± 4, respectively. The GI of the control granola, and granolas with 2.5 and 5 g of NVP were 64 ± 6, 33 ± 5, and 22 ± 3 respectively. GRIP was 6.8 ± 0.9 units per/g of NVP.

CONCLUSION

Sprinkling or incorporation of NVP into a variety of different foods is highly effective in reducing postprandial glycemia and lowering the GI of a food.

CLINICAL TRIAL REGISTRATION

NCT00935350.

Reduction of postprandial glycemia by the novel viscous polysaccharide PGX, in a dose-dependent manner, independent of food form

OBJECTIVE

Health benefits of viscous fiber intake are well established; nevertheless few effective and palatable preparations are available. The objective of the study therefore was to determine palatability and effectiveness of escalating doses of PGX, a novel viscous polysaccharide (NVP), in reducing postprandial glycemia when added to a liquid and a solid meal.

DESIGN

Two open-label, randomized, controlled trials were undertaken.

SETTING

Glycemic Index Laboratories, Inc, Toronto, Ontario, Canada.

SUBJECTS

Two groups of 10 healthy subjects each (group 1: 5 M, 5 F; 35.6 +/- 13.2 y; 24.6 +/- 2.1 kg/m(2); and group 2: 3 M, 7 F; 33.5 +/- 11.1 y; 26.3 +/- 5.2 kg/m(2)) were studied.

INTERVENTIONS

Zero, 2.5, 5, and 7.5 g of NVP were added to a glucose drink (group 1) or to white bread and margarine (WB + Marg) (group 2). Subjects repeated glucose control (group 1) or WB control (group 2) 3 times to allow calculation of the glycemic index (GI). Measures of Outcomes: Palatability of foods and capillary blood glucose concentrations were measured fasting and at 15, 30, 45, 60, 90, and 120 minutes after the start of the meal.

RESULTS

Addition of NVP to the meal reduced blood glucose incremental areas under the curve irrespective of dose, reaching significance at the 7.5 g dose when added to glucose (p < 0.01), and at the 5 and 7.5 g doses when added to WB + Marg (p < 0.001). The GI values of glucose with 0, 2.5, 5, or 7.5 g of NVP were (mean +/- standard error of the mean [SEM]) 100.0 +/- 0.0, 83.7 +/- 9.0, 77.7 +/- 8.2, and 72.5 +/- 5.9, respectively; the GI of the WB alone, or of WB + Marg, with 0, 2.5, 5, or 7.5 g of NVP was 71.0 +/- 0.0, 66.8 +/- 3.0, 47.5 +/- 5.9, 37.3 +/- 5.9, and 33.9 +/- 3.6, respectively.

CONCLUSION

Addition of NVP to different food matrices is highly effective in lowering the glycemic index of a food in a dose-responsive manner.

High-molecular-weight barley beta-glucan in chapatis (unleavened Indian flatbread) lowers glycemic index

Food products incorporated with soluble dietary fiber beta-glucan have shown varying effects on postprandial glycemia. The objective of the present study was to test the hypothesis that a food product fortified with barley beta-glucan and subjected to minimum processing and mild cooking might be effective in lowering glycemic response. In a randomized, single-blind, controlled crossover trial, 8 healthy human subjects (3 men, 5 women; aged 26-50 years; body mass index, <30 kg/m(2)) consumed unleavened Indian flatbreads called chapatis containing high-molecular-weight barley beta-glucan at doses of 0, 2, 4, 6, and 8 g on different occasions. Capillary blood samples were collected at 0, 15, 30, 45, 60, 90, and 120 minutes after consuming the chapatis. The incremental area under the glucose curve values for all the 5 different types of chapatis were significantly low (P < .001) compared with reference food glucose. The incremental area under the glucose curve of chapatis containing 4 and 8 g beta-glucan were significantly lower than control chapatis (P < .05). Postprandial blood glucose was significantly reduced at 45 minutes by chapatis containing 4 g (P < .05) and 8 g beta-glucan (P < .01) and at 60 minutes by chapatis with 8 g beta-glucan (P < .01). The glycemic index (GI) values of chapatis with 4 and 8 g beta-glucan were 43% to 47% lower (GI, 30 and 29, respectively) compared with chapatis without beta-glucan (GI, 54). We conclude that barley beta-glucan significantly reduces GI of chapatis, particularly at doses of 4 and 8 g per serving.

Comparable postprandial glucose reductions with viscous fiber blend enriched biscuits in healthy subjects and patients with diabetes mellitus: acute randomized controlled clinical trial

AIM

To compare the blood glucose-lowering effect of a highly viscous fiber blend (VFB) added to a starchy snack on postprandial glycemia between healthy participants and participants with diabetes mellitus.

METHODS

Ten healthy participants (4 men and 6 women, aged 28+/-2.6 years, body mass index [BMI], 24.3+/-0.8 kg/m(2)) and 9 participants with diabetes mellitus type 2 (3 men and 6 women, aged 68+/-3.8 years, BMI 28.8+/-1.2 kg/m(2)) on four separate occasions took either 50 g available carbohydrates as control biscuits, biscuits with 10 g of highly viscous fiber blend, white bread with 12 g of margarine, or white bread alone. Postprandial blood glucose response, glycemic index (GI), and palatability were determined.

RESULTS

Mean (95% confidence interval) GI values of the viscous fiber blend biscuits were 26 (16-36) and 37 (27-47) GI units for healthy participants and participants with diabetes mellitus, respectively. These values were significantly lower than those of white bread, white bread with 12 g of margarine, and control biscuits (P<0.001, paired t test) both in healthy participants (GI 100, 108 [57-159], and 101 [44-158], respectively) and participants with diabetes mellitus (GI 100, 103 [79-127], and 94 [78-110], respectively). Viscous fiber blend significantly reduced the glycemic index by 74% (7.4 GI units/g of fiber) in healthy participants and by 63% (6.3 GI units/g of fiber) in participants with diabetes. The GI did not differ between control meals in both healthy participants and participants with diabetes. There were no significant differences in palatability among the types of meals, although participants with diabetes found the viscous fiber blend biscuits more palatable (P=0.002, t test).

CONCLUSION

Viscous fiber blend is a very potent and palatable soluble fiber addition to a starchy snack, which is able to reduce the glycemic response to a similar extent in both healthy participants and individuals with diabetes mellitus. Biscuits with low GI, and possibly other viscous fiber blend fortified starchy foods, may potentially be a useful replacement of high GI snack foods in the diet.

Dietary Fiber and the Relationship to Chronic Diseases

Preventative medicine is targeting chronic diseases such as heart disease, cancer, diabetes, and obesity. Populations that consume more dietary fiber have less chronic disease. Intake of dietary fiber has beneficial effects on the risk factors for developing several chronic diseases. Dietary reference intakes recommend the consumption of 14 g of dietary fiber per 1000 kcal, or 25 g for women and 38 g for men, based on the goal of protection against cardiovascular disease. Usual intake of dietary fiber is only 16 g per day. Viscous fibers decrease the glycemic response and may assist in diabetes care. High-fiber diets provide bulk, are more satiating, and have been linked to lower body weights. Evidence that fiber decreases cancer is mixed, and further research is needed. Dietary messages to increase consumption of high-fiber foods such as whole grains, legumes, fruits, and vegetables should be broadly supported by the medical profession. Consumers are also turning to fiber supplements and bulk laxatives as additional fiber sources. As many fiber supplements have not been studied for physiological effectiveness, the best advice is to consume fiber in foods.

Breakfast cereals and risk of type 2 diabetes in the Physicians' Health Study I

OBJECTIVE

To examine the association between breakfast cereal consumption and the risk of type 2 diabetes (DM).

RESEARCH METHODS AND PROCEDURES

We analyzed prospectively data from 21,152 male participants of the Physicians' Health Study I. Consumption of breakfast cereals was estimated using an abbreviated food questionnaire, and incident DM was ascertained through yearly follow-up questionnaires.

RESULTS

The average age was 53.6 +/- 9.4 years (range, 39.7 to 85.9) during the initial assessment of cereal intake (1981 to 1983). During a mean follow-up of 19.1 years, 1958 cases of DM occurred. The crude incidence rates of DM were 57.7, 53.8, 43.5, and 35.4 cases/10,000 person-years for people reporting breakfast cereal intake of 0, <or=1, 2 to 6, and >or=7 servings/wk, respectively. In a Cox regression model adjusting for age, cigarette smoking, BMI, physical activity, vegetable consumption, and alcohol intake, hazard ratios (95% confidence interval) for DM were 1.0 (reference), 0.89 (0.79 to 1.00), 0.76 (0.67 to 0.86), and 0.63 (0.55 to 0.72) from the lowest to the highest category of cereal consumption, respectively (p for trend < 0.0001). In secondary analyses, the inverse association between cereal intake and DM was stronger with whole-grain than refined cereals.

DISCUSSION

These results suggest that intake of breakfast cereals might confer a lower risk of DM. Consumption of whole-grain products may help lower the risk of DM.

Effect of commercial breakfast fibre cereals compared with corn flakes on postprandial blood glucose, gastric emptying and satiety in healthy subjects: a randomized blinded crossover trial

Background

Dietary fibre food intake is related to a reduced risk of developing diabetes mellitus. However, the mechanism of this effect is still not clear. The aim of this study was to evaluate the effect of commercial fibre cereals on the rate of gastric emptying, postprandial glucose response and satiety in healthy subjects.

Methods

Gastric emptying rate (GER) was measured by standardized real time ultrasonography. Twelve healthy subjects were assessed using a randomized crossover blinded trial. The subjects were examined after an 8 hour fast and after assessment of normal fasting blood glucose level. Satiety scores were estimated and blood glucose measurements were taken before and at 0, 20, 30, 40, 60, 80, 100 and 120 min after the end of the meal. GER was calculated as the percentage change in the antral cross-sectional area 15 and 90 min after ingestion of sour milk with corn flakes (GER1), cereal bran flakes (GER2) or wholemeal oat flakes (GER3).

Results

The median value was, respectively, 42% for GER1, 33 % for GER2 and 51% for GER3. The difference between the GER after ingestion of bran flakes compared to wholemeal oat flakes was statistically significant (p = 0.023). The postprandial delta blood glucose level was statistically significantly lower at 40 min (p = 0.045) and 120 min (p = 0.023) after the cereal bran flakes meal. There was no statistical significance between the areas under the curve (AUCs) of the cereals as far as blood glucose and satiety were concerned.

Conclusion

The result of this study demonstrates that the intake of either bran flakes or wholemeal oat flakes has no effect on the total postprandial blood glucose response or satiety when compared to corn flakes. However, the study does show that the intake of cereal bran flakes slows the GER when compared to oat flakes and corn flakes, probably due to a higher fibre content. Since these products do not differ in terms of glucose response and satiety on healthy subjects, they should be considered equivalent in this respect.

Trial registration

ISRCTN90535566