Clinical Care/Education/Nutrition ORIGINAL ARTICLE Consumption of Both Resistant Starch and ␤-Glucan Improves Postprandial Plasma Glucose and Insulin in Women 1 1 KAY M. BEHALL, PHD JUDITH G. HALLFRISCH, PHD conditions make direct comparison of 1 2 DANIEL J. SCHOLFIELD, MS HELENA G.M. LILJEBERG-ELMSTÅHL, PHD studies difficult (3,8). Hyperinsulinemia, an indication of insulin resistance, is one indicator of the OBJECTIVE — Consumption of a meal high in resistant starch or soluble fiber (␤-glucan) potential to develop type 2 diabetes decreases peak insulin and glucose concentrations and areas under the curve (AUCs). The (9,10). Abnormal carbohydrate metabo- objective was to determine whether the effects of soluble fiber and resistant starch on glycemic lism, especially with respect to elevated variables are additive. glucose or insulin concentrations in the blood, occurs with increasing age and RESEARCH DESIGN AND METHODS — Ten normal-weight (43.5 years of age, BMI 2 2 weight (10,11). Insulin resistance (abnor- 22.0 kg/m ) and 10 overweight women (43.3 years of age, BMI 30.4 kg/m ) consumed 10 mal glucose metabolism and/or hyperin- tolerance meals in a Latin square design. Meals (1 g carbohydrate/kg body wt) were glucose alone or muffins made with different levels of soluble fiber (0.26, 0.68, or 2.3 g ␤-glucan/100 g muffin) sulinemia) increases as weight increases and three levels of resistant starch (0.71, 2.57, or 5.06 g/100 g muffin). and is more prevalent in obese subjects (up to 46% in obese subjects compared RESULTS — Overweight subjects had plasma insulin concentrations higher than those of with 4% in a control population) (12). normal-weight subjects but maintained similar plasma glucose levels. Compared with low ␤- Objectives of this study include as- glucan–low resistant starch muffins, glucose and insulin AUC decreased when ␤-glucan (17 and sessment of the effect of various levels of 33%, respectively) or resistant starch (24 and 38%, respectively) content was increased. The resistant starch (from high-amylose corn- greatest AUC reduction occurred after meals containing both high ␤-glucan–high resistant starch) and soluble fiber (␤-glucan from starch (33 and 59% lower AUC for glucose and insulin, respectively). Overweight women were Oatrim) on the improvement of glycemic somewhat more insulin resistant than control women. response and insulin sensitivity in nor- CONCLUSIONS — Soluble fiber appears to have a greater effect on postprandial insulin mal-weight and overweight or obese response while glucose reduction is greater after resistant starch from high-amylose cornstarch. adults and determination of whether an The reduction in glycemic response was enhanced by combining resistant starch and soluble interaction between the two carbohydrate fiber. Consumption of foods containing moderate amounts of these fibers may improve glucose sources might retard or improve glycemic metabolism in both normal and overweight women. response. The hypothesis of the study is that the effects of ␤-glucan and resistant Diabetes Care 29:976–981, 2006 starch are additive. variety of fiber components, espe- tragacanth, and methyl cellulose fibers, RESEARCH DESIGN AND cially soluble fiber and resistant when compared with meals without sol- METHODS — Twenty women were A starch, have beneficial effects on uble fiber (1,4). selected for the study after clinical analy- glucose tolerance in people with normal Increased amylose or resistant sis of fasting blood and urine samples and as well as impaired glucose tolerance starch (high amylose versus amylopec- a medical evaluation of their health his- (1,2). These effects include reductions in tin) decreased postprandial glucose and tory. Subjects were selected based on the blood glucose and insulin (1,3) and im- insulin responses in people with either following criteria: 1) weight stable for 6 provement of glycemic control in diabetes normal glucose tolerance or impaired months before the study, 2) normoten- (2). Glucose and insulin responses im- glucose tolerance (3,5–8). Different sive, 3) nondiabetic fasting glucose, 4)no proved (decreased) after test meals con- amounts of resistant starch or high- history of disease affecting carbohydrate taining soluble fibers, including pectin, amylose starch consumed in the meals metabolism, 5) taking no medication Oatrim (oat fiber extract), guar gum, gum as well as different recipes and storage known to affect glucose or lipid metabo- ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● lism, and 6) no current disease found by a routine urinalysis and blood screen. Con- From the 1Diet and Human Performance Laboratory, Beltsville Human Nutrition Research Center, Agricul- tural Research Service, U.S. Department of Agriculture, Beltsville, Maryland; and the 2Center for Chemistry trol subjects averaged 43.4 years old, 61.6 2 and Chemical Engineering, Lund University, Lund, Sweden. kg, with BMI 22.0 kg/m , 29.7% body fat, Address correspondence and reprint requests to Kay M. Behall, Building 307B, BARC-East, Diet and fasting glucose 4.92 mmol/l, and triglyc- Human Performance Laboratory, Beltsville Human Nutrition Research Center, ARS, USDA, Beltsville, MD erides 0.98 mmol/l. Overweight women 20705-2350. E-mail: [email protected]. Received for publication 19 October 2005 and accepted in revised form 18 January 2006. were paired for age with control subjects Abbreviations: AUC, area under the curve; HOMA, homeostasis model assessment. and averaged 43.3 years old, 81.7 kg, A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion with BMI 30.4 kg/m2, 37.6% body fat, factors for many substances. fasting glucose 5.01 mmol/l, and triglyc- DOI: 10.2337/dc05-2012 erides 1.20 mmol/l. The design and pur- © 2006 by the American Diabetes Association. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby pose of the study were explained to the marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. subjects both orally and in writing. The 976 DIABETES CARE, VOLUME 29, NUMBER 5, MAY 2006 Behall and Associates study was approved to include both men enzyme hydrolysate as determined by tween the groups of control and over- and women by the institutional review high-performance anion exchange weight women were ϳ0.08, 0.2, and board of The Johns Hopkins University chromatography (13). The ␤-glucan con- 1.0 g for the three levels of ␤-glucan, re- Bloomberg School of Public Health. Due tent of the Oatrim was determined enzy- spectively and 0.2, 0.8, and 1.6 for the to facility and staff limitations, women matically by AACC (American three levels of resistant starch, respec- were studied first. Association of Cereal Chemists) method tively. These differences in intake do not Subjects were given a standard equil- 32-23 (14). appear to have affected results, since there ibration diet containing 30% fat, 55% car- were minimal differences between the bohydrate, and 15% protein for 2 days Data calculations and statistical groups. before and the day of sample collection. analyses Significant differences were observed Body weight was used to determine en- Power analysis for sample size has deter- in plasma glucose concentrations (Table ergy intake for the controlled diet, and mined that a 10% difference in insulin 1) after the 10 meals were consumed subjects consumed that same amount of response, a critical variable in testing the (time, P Ͻ 0.001; treatment-by-time in- energy during all 10 periods. The menu hypothesis, can be detected with n ϭ 8in teraction, P Ͻ 0.009). Since there was no was identical before each tolerance. Sub- each group with a significance level of P Ͻ statistically significant group (P ϭ 0.869), jects consumed their self-selected diets 0.05. However, to ensure power to reach group by treatment (P ϭ 0.089), or group between tolerance meals. desired statistical outcomes and allow for by time (P ϭ 0.746), the two groups of Blood was collected after a 10 h fast. voluntary withdrawal, we increased the women were combined. Plasma glucose Subjects then consumed 1 g carbohy- number of subjects to 10 per group. concentrations of the combined weight drate/kg body wt either as a glucose solu- When samples were analyzed after the groups after the glucose were higher at 2 h tion plus 100 g water or a test muffin study, one control and one overweight and lower at 3 h than after the test meals. containing an equal amount of total car- woman were found to have abnormal glu- Glucose concentration at2hafterthe bohydrate plus water equal to that in the cose concentrations. Analyses were rerun high–␤-glucan/high–resistant starch glucose tolerance. Nine muffin types were eliminating the data from these women. meal was significantly lower than after made that contained either 1) standard Insulin resistance was calculated using meals with low or medium ␤-glucan. Glu- cornstarch, 2) a 50/50 blend of standard the homeostasis model assessment cose concentrations at 1 h after the meals ␮ and high-amylose cornstarches, or 3) (HOMA ϭ insulin U/ml ϫ glucosemmol/l/ were lowest after the high–␤-glucan/ high-amylose cornstarch providing 0.71, 22.5) (15) and a method using a pub- high– and mid–resistant starch meals. 2.57, or 5.06 g resistant starch/100 g muf- lished index of glucose disposal rates Insulin responses (Table 2) were sig- fin, respectively. Each of the three corrected for fat-free mass (FFM) based nificantly affected by treatment (P Ͻ starches was combined with Oatrim (1, on fasting insulin and triglyceride con- 0.001), time (P Ͻ 0.0001), and treat- 2.5, or 10% ␤-glucan by weight) provid- centrations {MFFM ϭ EXP[2.63 Ϫ 0.28 ment-by-time interaction (P Ͻ 0.04).