Increasing oat β-glucan viscosity in a breakfast meal slows gastric emptying and reduces glycemic and insulinemic responses but has no effect on appetite, food intake, or plasma ghrelin and PYY responses in healthy humans: a randomized, placebo-controlled, crossover trial

• Published in: The American journal of clinical nutrition Vol. 111; no. 2; pp. 319 - 328
• Main Authors: Wolever, Thomas MS, Tosh, Susan M, Spruill, Susan E, Jenkins, Alexandra L, Ezatagha, Adish, Duss, Ruedi, Johnson, Jodee, Chu, YiFang, Steinert, Robert E
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2020; Oxford University Press; American Society for Clinical Nutrition, Inc
• Subjects: Adolescent; Adult; Appetite; Appetite - drug effects; Avena; beta-Glucans - administration & dosage; beta-Glucans - chemistry; blood glucose; Blood Glucose - drug effects; Breakfast; Cholesterol; Cross-Over Studies; Diabetes mellitus; dietary carbohydrates; Double-Blind Method; Eating - drug effects; Emptying; Female; Females; Food; Food intake; Gastric emptying; Ghrelin; Ghrelin - blood; Glucan; Glucose; gut hormones; Humans; Insulin; Insulin - blood; Male; Males; Meals; Middle Aged; Milk; Molecular weight; Oats; Peptide YY - blood; Pizza; postprandial response; Randomization; randomized clinical trial; Tyrosine; Viscosity; Young Adult; β-Glucan; dietary carbohydrates; blood glucose; insulin; kDa; VAS; cP; 4gOBG; 2gOBG; T; OBG; Tlag; β-glucan; oats; GI; GLP-1; IMI; postprandial response; netAUC; randomized clinical trial; MW; FIR; CR; INQUIS; PYY; iAUC; gut hormones; appetite; 4gloMW; food intake
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/nqz285

The viscosity of oat β-glucan (OBG) determines its effect on serum cholesterol and glycemic responses, but whether OBG viscosity affects gastric emptying, appetite, and ad libitum food intake is unknown.
We aimed to determine the effect of altering the amount or molecular weight (MW) and, hence, viscosity of OBG in a breakfast meal on the primary endpoint of food intake at a subsequent meal.
Overnight-fasted males (n = 16) and nonpregnant females (n = 12) without diabetes, aged 18–60 y, with BMI 20.0–30.0 kg/m² who were unrestrained eaters participated in a double-blind, randomized, crossover study at a contract research organization. Participants consumed, in random order, breakfast meals equivalent in weight, energy, and macronutrients consisting of white-bread, butter, jam, and 2% milk plus hot cereal [Cream of Rice (CR), or instant-oatmeal plus either 3 g oat-bran (2gOBG), 10 g oat-bran (4gOBG), or 10 g oat-bran plus β-glucanase (4gloMW) to reduce OBG MW and viscosity compared with 4gOBG]. Gastric emptying, subjective appetite, and glucose, insulin, ghrelin, and peptide tyrosine tyrosine (PYY) responses were assessed for 3 h and then subjects were offered an ad libitum lunch (water and pizza).
Pizza intakes (n = 28) after CR, 2gOBG, 4gOBG, and 4gloMW (mean ± SEM: 887 ± 64, 831 ± 61, 834 ± 78, and 847 ± 68 kcal, respectively) were similar (nonsignificant). Compared with CR, 4gOBG significantly reduced glucose (78 ± 10 compared with 135 ± 15 mmol × min/L) and insulin (14.0 ± 1.6 compared with 26.8 ± 3.5 nmol × min/L) incremental area-under-the-curve and delayed gastric-emptying half-time (geometric mean: 285; 95% CI: 184, 442, compared with geometric mean: 105; 95% CI: 95, 117 min), effects not seen after 4gloMW. Subjective appetite, PYY, and ghrelin responses after 2gOBG, 4gOBG, and 4gloMW were similar to those after CR.
The results demonstrate that OBG viscosity determines its effect on postprandial glucose, insulin, and gastric emptying. However, we were unable to demonstrate a significant effect of OBG on appetite or food intake, regardless of its viscosity. This trial was registered at clinicaltrials.gov as NCT03490851.