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Clinical Care/Education/Nutrition BRIEF REPORT

Glycemic Index–Based Nutritional Education Improves Blood Control in Japanese Adults A randomized controlled trial

1,2 1 YUKI AMANO, PHD KATSUMI MORI, BSC Changes in outcomes were assessed by re- 3 5 MICHIKO SUGIYAMA, PHD ANN C. TANG, PHD peated-measures two-way ANOVA. The 1 1 JUNG S. LEE, PHD AKIRA AKABAYASHI, MD, PHD 4 statistical significance standard was 5%. KIYOSHI KAWAKUBO, MD, PHD RESULTS — Of the 40 participants, 19 and 21 were placed in the GI and conven- low–glycemic index (GI) diet is ef- Conventional nutritional education tional groups, respectively. One from the fective in lowering A1C in diabetic was based on the Japan Society conventional group withdrew in the first A patients (1–3). However, most re- guidelines (4) and focused on lowering total month. All of the 39 remaining partici- search is from Western countries, where energy intake, mainly by reducing fat intake pants attended all sessions, took all re- and wheat are the main sources of or eliminating snacking. The GI-based nu- quired measurements, and submitted all . A GI-based nutrition edu- trition education aimed to train participants of their dietary records. cation program, designed for people who to consume one-half or more of their daily A1C improved more in the GI group consume white (a high-GI food) as intake from low-GI foods than in the conventional group (Table 1). Ϫ Ϯ the staple, has not yet been studied. We (1,5–7). Because the main determinant of The average changes in A1C were 0.46 Ϫ Ϯ developed a low-GI dietary regimen dietary GI is the (5,8), education 0.33% in the GI group and 0.21 0.43% based on Japanese foods. This study focused on the selection of low-GI staple in the conventional group, and the effect Ϫ aimed to evaluate whether GI-based nu- foods. Participants were instructed to com- size due to intervention was 0.25 (95% CI Ϫ Ϫ trition education improves blood glucose bine the high-GI staple foods with vinegar 0.50 to 0.004). control more than a conventional nutri- (7,9–12), dairy products (7,13,14), or fer- FPG, total and LDL cholesterol, and tion education in participants with type 2 mented foods such as yogurt and pickles body weight and fat decreased signifi- diabetes or impaired fasting glucose. (7,15) to reduce postprandial blood glucose cantly in both groups. Carbohydrate from low-GI foods and combination of high-GI RESEARCH DESIGN AND spikes. staple foods with vinegar or other foods METHODS After a 12-h fasting, blood samples — We conducted a 3- increased more in the GI group than in month, randomized, controlled, parallel- were collected and immediately refrigerated and transported for analyses to the Health the conventional group. In both groups, group trial. Participant inclusion criteria dietary GI, total energy, and cholesterol were as follows: 1) fasting plasma glucose Science Research Institute. Under the same condition, height, weight, and fat were as- intake significantly decreased and dietary (FPG) between 110 and 160 mg/dl or fiber intake significantly increased. A1C between 5.8 and 8.0% (4) and 2) sessed by stadiometer (YG200; Yagami) or nonusage of any hypoglycemic drugs. bioelectric impedance (BF-616; Tanita) CONCLUSIONS — According to a All participants attended one group ses- without shoes. Dietary intake was assessed Cochrane meta-analysis, dietary advice plus sion on conventional nutritional education with a 3-day dietary record. Dietary GI was exercise is associated with a mean 0.9% de- at baseline. Each participant was then ran- calculated by a method we described previ- crease in A1C at 6 months among type 2 domly assigned to either GI-based or con- ously (5). All analyses were performed us- diabetic patients (16). For the general pop- ventional nutrition education; four ing SAS (version 9.1; SAS Institute, Cary, ulation, a 0.3% decrease in A1C may well individual sessions followed (2nd week and NC). Baseline differences between groups have significant health benefits (17). Our 1st, 2nd, and 3rd month). were assessed by an unpaired t test. findings showed a posteducation difference ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● of 0.25% in reduced A1C between the From the 1Department of Health Promotion Sciences, Graduate School of Medicine, The University of 2 3 groups, despite a solely nutritional educa- Tokyo, Tokyo, Japan; the Japan Society for the Promotion of Science, Tokyo, Japan; the School of Nutrition tion–based strategy and a short duration of and Dietetics, Kanagawa University of Human Services, Kanagawa, Japan; the 4Department of Food Sciences and Nutrition, Kyoritsu Women’s University, Tokyo, Japan; and the 5Department of Medical Education, the intervention. Participants in the GI Tokyo Women’s Medical University, Tokyo, Japan. group may have shown further reduction in Address correspondence and reprint requests to Dr. Yuki Amano, Department of Health Promotion A1C over a longer period. Sciences, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113- This is the first study to develop a GI- 0033, Japan. E-mail: [email protected]. Received for publication 19 October 2006 and accepted in revised form 2 April 2007. based nutritional education program for in- Published ahead of print at http://care.diabetesjournals.org on 17 April 2007. DOI: 10.2337/dc06-2151. dividuals whose staple food is . Abbreviations: FPG, fasting plasma glucose; GI, glycemic index. Although replacing white rice with low-GI A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion staple foods can increase fat intake (5), the factors for many substances. GI group decreased energy intake without © 2007 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 increasing fat intake. Furthermore, dietary marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. indexes related to GI significantly improved

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Table 1—Metabolic parameters and dietary data over the 3-month period for the GI-based conventional nutritional education groups Amano and Associates GI group (n ϭ 19) Conventional (n ϭ 20) P for main effect* P for group 0 month† 2 months 3 months 0 month† 2 months 3 months Group Time ϫ time* Metabolic parameters A1C (%) 6.51 Ϯ 0.82 6.20 Ϯ 0.80 6.05 Ϯ 0.70 6.29 Ϯ 0.57 6.06 Ϯ 0.44 6.08 Ϯ 0.44 0.631 Ͻ0.001 0.046 FPG (mg/dl) 131.3 Ϯ 14.3 122.0 Ϯ 15.3 124.3 Ϯ 17.3 133.1 Ϯ 17.2 125.3 Ϯ 18.0 122.8 Ϯ 13.2 0.803 Ͻ0.001 0.404 IRI (␮U/ml) 7.75 Ϯ 4.13 8.11 Ϯ 5.72 7.49 Ϯ 5.08 9.82 Ϯ 6.97 7.88 Ϯ 4.34 6.88 Ϯ 3.66 0.782 0.054 0.098 Cholesterol (mg/dl) Total 215.0 Ϯ 39.3 208.1 Ϯ 36.6 207.7 Ϯ 34.4 213.1 Ϯ 34.5 195.3 Ϯ 23.1 198.5 Ϯ 29.0 0.429 Ͻ0.001 0.215 LDL 139.4 Ϯ 30.9 133.1 Ϯ 28.1 134.7 Ϯ 30.6 131.7 Ϯ 32.7 117.5 Ϯ 23.6 119.8 Ϯ 28.8 0.153 0.001 0.323 HDL 59.6 Ϯ 10.2 58.6 Ϯ 9.6 59.3 Ϯ 9.8 61.5 Ϯ 13.7 60.1 Ϯ 14.4 60.0 Ϯ 15.3 0.730 0.362 0.826 Triglyceride (mg/dl) 112.6 Ϯ 88.3 107.8 Ϯ 90.5 95.3 Ϯ 67.2 146.5 Ϯ 80.5 130.9 Ϯ 66.2 134.6 Ϯ 89.1 0.193 0.185 0.593 Weight (kg) 62.5 Ϯ 14.2 60.9 Ϯ 13.9 60.3 Ϯ 13.5 60.3 Ϯ 8.4 59.0 Ϯ 7.7 58.6 Ϯ 7.5 0.592 Ͻ0.001 0.611 Body fat (%) 29.6 Ϯ 7.5 28.2 Ϯ 7.4 27.8 Ϯ 6.4 28.7 Ϯ 6.7 28.0 Ϯ 7.7 27.6 Ϯ 7.7 0.859 Ͻ0.001 0.538 BMI (kg/m2 ) 24.7 Ϯ 4.1 24.1 Ϯ 3.7 23.8 Ϯ 3.5 24.2 Ϯ 2.0 23.6 Ϯ 1.8 23.5 Ϯ 1.8 0.645 Ͻ0.001 0.467 Dietary GI‡ 68.5 Ϯ 5.2 64.7 Ϯ 5.3 61.8 Ϯ 5.6 70.2 Ϯ 5.2 68.9 Ϯ 6.0 68.1 Ϯ 5.2 0.001 Ͻ0.001 0.066 Values related to GI Carbohydrate from low GI foods 31.3 Ϯ 12.9 41.8 Ϯ 15.5 50.0 Ϯ 14.2 29.1 Ϯ 12.3 32.0 Ϯ 16.0 35.1 Ϯ 12.6 0.005 Ͻ0.001 0.032 (%)§ Combination of high GI staple 43.9 Ϯ 20.1 63.9 Ϯ 25.8 65.5 Ϯ 23.7 47.8 Ϯ 24.2 49.2 Ϯ 24.2 46.4 Ϯ 21.3 0.112 0.065 0.035 foods with vinegar or other foods (%)§¶ Nutritional intake Total energy (kcal) 1,892.2 Ϯ 256.4 1,834.7 Ϯ 375.8 1,777.6 Ϯ 329.7 1,905.3 Ϯ 413.9 1,792.1 Ϯ 335.4 1,714.1 Ϯ 303.5 0.883 0.001 0.549 Protein (% of calories) 17.0 Ϯ 2.4 16.8 Ϯ 2.4 16.9 Ϯ 2.1 14.6 Ϯ 2.1 15.8 Ϯ 1.7 15.8 Ϯ 3.0 0.012 0.208 0.261 Total fat (% of calories) 25.0 Ϯ 5.0 23.7 Ϯ 4.6 23.4 Ϯ 4.6 25.0 Ϯ 6.1 24.6 Ϯ 5.4 23.0 Ϯ 4.8 0.953 0.149 0.760 2007

Carbohydrate (% of calories) 58.0 Ϯ 5.8 59.5 Ϯ 4.3 59.7 Ϯ 4.5 60.4 Ϯ 6.5 59.6 Ϯ 6.0 61.3 Ϯ 6.1 0.303 0.476 0.630 ULY

Dietary fiber (g/1,000 kcal) 9.3 Ϯ 2.5 11.7 Ϯ 3.0 11.1 Ϯ 2.6 8.4 Ϯ 2.2 9.8 Ϯ 3.9 10.3 Ϯ 3.2 0.082 Ͻ0.001 0.236 7, J Cholesterol (mg) 370.1 Ϯ 131.3 287.7 Ϯ 128.9 281.8 Ϯ 108.3 353.5 Ϯ 130.7 321.8 Ϯ 116.5 294.2 Ϯ 90.5 0.478 0.002 0.414 Data are means Ϯ SD unless otherwise indicated. *Repeated-measures two-way ANOVA. †No significant differences were observed in the participants’ baseline characteristics between the GI and the conventional NUMBER groups. ‡Glucose-based values. §Foods with a white rice–based GI Յ70 (glucose-based GI 56) were considered low-GI foods, while foods with a white rice–based GI of Ն85 (glucose-based GI 68) were considered high-GI foods. ¶Proportion of combining high-GI staple foods with vinegar or other foods that decrease postprandial glycemia (times of combination/times of having high GI foods as the staple food). IRI, 30, immunoreactive . VOLUME , ARE C IABETES D GI education and glucose control in the GI group, suggesting good adherence nese foods with white rice as a reference the Framingham offspring cohort. Diabe- to the program. food. Eur J Clin Nutr 57:743–752, 2003 tes Care 27:538–546, 2004 Our findings did not show a significant 8. Murakami K, Sasaki S, Takahashi Y, 20. Buyken AE, Toeller M, Heitkamp G, Kara- difference in the change over time in FPG, Okubo H, Hosoi Y, Horiguchi H, Oguma manos B, Rottiers R, Muggeo M, Fuller JH: insulin, lipid metabolism, or body weight E, Kayama F: Dietary glycemic index and Glycemic index in the diet of European load in relation to metabolic risk factors in outpatients with type 1 diabetes: relations between the groups. Many studies have Japanese female farmers with traditional to glycated hemoglobin and serum lipids. shown that low-GI diets are associated with dietary habits. Am J Clin Nutr 83:1161– Am J Clin Nutr 73:574–581, 2001 changes in glucose metabolism (5,18–20), 1169, 2006 21. Liu S, Manson JE, Stampfer MJ, Holmes lipid metabolism (5,20–23), and body 9. Brighenti F, Castellani G, Benini L, Casir- MD, Hu FB, Hankinson SE, Willett WC: weight or fat (24–28). However, the con- aghi MC, Leopardi E, Crovetti R, Testolin Dietary assessed by food- clusions of these associations are controver- G: Effect of neutralized and native vinegar frequency questionnaire in relation to sial (2,3,29,30). Further research to on blood glucose and acetate responses to plasma high-density-lipoprotein choles- elucidate these relationships is needed. a mixed meal in healthy subjects. Eur terol and fasting plasma triacylglycerols in The major limitation of our study was J Clin Nutr 49:242–247, 1995 postmenopausal women. Am J Clin Nutr its small sample size. This may explain the 10. Leeman M, Ostman E, Bjorck I: Vinegar 73:560–566, 2001 dressing and cold storage of potatoes low- 22. Ford ES, Liu S: Glycemic index and serum nonsignificant differences between the two ers postprandial glycaemic and insulinae- high-density lipoprotein cholesterol con- groups in baseline values. To generalize the mic responses in healthy subjects. Eur centration among US adults. Arch Intern study findings, a larger sample is needed. J Clin Nutr 59:1266–1271, 2005 Med 161:572–576, 2001 In conclusion, GI-based nutrition ed- 11. Liljeberg H, Bjorck I: Delayed gastric 23. Frost G, Leeds AA, Dore CJ, Madeiros S, ucation is effective in improving blood emptying rate may explain improved gly- Brading S, Dornhorst A: Glycaemic index glucose control in participants with type 2 caemia in healthy subjects to a starchy as a determinant of serum HDL-choles- diabetes or impaired fasting glucose. The meal with added vinegar. Eur J Clin Nutr terol concentration. 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