High β-Glucan Barley Improves Postprandial Hyperglycemia after Meal Loading in Patients with Type 2 Diabetes

Research Article

Austin J Nutr Metab. 2021; 8(2): 1104.

High β-Glucan Barley Improves Postprandial Hyperglycemia after Meal Loading in Patients with Type 2 Diabetes

Yukie Fuse1,2, Mariko Higa2*, Asami Fujitani3, Takamasa Ichijo2, Seiichiro Aoe4 and Takahisa Hirose1

1Division of Diabetes, Metabolism, and Endocrinology, Department of Medicine, Toho University Graduate School of Medicine, Tokyo, Japan

2Division of Diabetes and Endocrinology, Department of Medicine, Saiseikai Yokohamashi Tobu Hospital, Kanagawa, Japan

3Nutrition Support Team, Saiseikai Yokohamashi Tobu Hospital, Kanagawa, Japan

4Department of Food Science, Faculty of Home Economics, Otsuma Women’s University, Tokyo, Japan

*Corresponding author: Mariko Higa, Division of Diabetes and Endocrinology, Department of Medicine, Saiseikai Yokohamashi Tobu Hospital, 3-6-1 Shimosueyoshi, Tsurumi-ku, Yokohama-shi, Kanagawa 230-0012, Japan

Received: February 09, 2021; Accepted: March 15, 2021; Published: March 22, 2021

Abstract

Objective: We investigated whether barley with a high β-glucan content (7.2 g per 100 g) improves postprandial plasma glucose levels and fluctuations using a meal tolerance test and Continuous Glucose Monitoring (CGM) in patients with type 2 diabetes.

Methods: A meal tolerance test (500 kcal) was conducted using two types of test meals: one with white rice (WR diet) and one with white rice mixed 1:1 with high β-glucan-containing barley (BR diet). Both meals included the same side dish. Plasma glucose changes over 180 minutes were compared after ingestion of the test meals. In addition, participants wore a CGM device for the 2 study days, to measure the daily variations in glucose levels when the WR or BR diet as staple food was provided 3 times a day with the same side dish in both meals.

Results: Twenty-nine patients with type 2 diabetes (age 52.5 ± 15.1 years, BMI 27.5 ± 4.7 kg/m2, HbA1c 8.1 ±1.8 %) were included in this study. The incremental area under the curve of plasma glucose levels after BR diet ingestion was significantly lower than that after WR diet ingestion (7934.0 ± 4151.2 vs 9434.0 ± 4701.2 mg·min/dL). CGM showed a 24-hour standard deviation of blood glucose after the BR diet was significantly lower than that after the WR diet.

Conclusion: These results suggest that postprandial plasma glucose elevation and fluctuation in patients with type 2 diabetes are suppressed by adding high-β-glucan barley to white rice in meals.

Keywords: Diet therapy; Beta glucan; Barley; Postprandial hyperglycemia; Type 2 diabetes

Introduction

The association between diabetes and a marked increase in the risk of coronary heart disease is well-established [1,2]. Although many factors are involved in the development of atherosclerosis and coronary heart disease, the two most important are hyperglycemia and insulin resistance [2,3]. There is growing evidence that the generation of oxidative stress and inflammation that occurs during postprandial hyperglycemia is an important mechanism for the initiation and progression of endothelial dysfunction in type 2 diabetes [3,4]. The postprandial increase in plasma glucose level is primarily governed by the amount of carbohydrate in the meal [5- 7] and may vary depending on the quality of the carbohydrate [8]. Carbohydrate quality is assessed by the Glycemic Index (GI), which ranks carbohydrates based on the rate of glycemic response [8]. A recent study revealed that dietary fiber intake was inversely associated with all-cause mortality [9]. Brown rice and barley have a lower GI value and suppress postprandial elevation of plasma glucose level because they contain a higher amount of dietary fiber than White Rice (WR) [10-12]. Barley, in particular, contains a high amount of insoluble and soluble dietary fiber, and most of the soluble dietary fiber is β-glucan [13,14], which may reduce the risk of cardiovascular diseases in part through its blood cholesterol-lowering action [15].

High intake of carbohydrate, including WR, causes an increase in postprandial plasma glucose level and is associated with an increased risk of cardiovascular disease, metabolic syndrome and diabetes [16,17]. Intake of high β-glucan barley leads to a reduction in visceral fat [18], and we previously showed that it suppressed postprandial plasma glucose elevation and oxidative stress, as well as reducing the mean blood glucose level over 24 hours, and blood glucose fluctuations, in volunteers with normal glucose tolerance [19].

Here, we conducted meal tolerance tests in patients with type 2 diabetes, using a test meal of WR mixed with two-rowed hull-less barley, which contains more β-glucan (7.2 g per 100 g) than common barley [20], to examine whether high β-glucan barley improves postprandial plasma glucose levels. In addition, Continuous Glucose Monitoring (CGM) system was used to assess blood glucose fluctuations of the day.

Materials and Methods

Study participants

Participants were recruited among patients admitted to Saiseikai Yokohamashi Tobu Hospital for diabetic control between January 2015 and August 2015. Twenty-nine patients with type 2 diabetes (15 men and 14 women) were included. The inclusion criteria were as follows: 1) age <75 years; 2) fasting plasma glucose levels ≤140 mg/ dL; 3) daily plasma glucose fluctuations <100 mg/dL as shown in Table 1. Patients diagnosed with severe renal dysfunction (estimated glomerular filtration rate <50 mL/min/1.73 m²) and/or serious cardiovascular diseases were excluded. Patients were also required to not have eaten food containing barley for 1 week prior to the study. This was confirmed using a dietary survey. Study participants had a mean age of 57.2 ± 15.1 years. Mean body mass index, fasting plasma glucose and HbA1c levels were 27.5 ± 4.7 kg/m², 119.3 ± 16.1 mg/dL, and 8.1 ± 1.8%, respectively. Three patients were treating their diabetes with diet alone, 15 patients were receiving insulin with oral hypoglycemic agents, and 11 patients were receiving oral hypoglycemic agents alone. Of the 29 patients treated with insulin or oral hypoglycemic agents, 14 were receiving a Dipeptidyl Peptidase-4 (DPP-4) inhibitor. All treatments, including oral antidiabetic agents and doses of insulin, remained unchanged throughout the study period.