European Journal of Clinical Nutrition (2003) 57, 743–752 & 2003 Nature Publishing Group All rights reserved 0954-3007/03 $25.00 www.nature.com/ejcn

ORIGINAL COMMUNICATION Glycemic index of single and mixed meal foods among common Japanese foods with white as a reference food

M Sugiyama1*, AC Tang2, Y Wakaki3 and W Koyama3

1National Institute of Health and Nutrition, ; 2Department of Health Promotion Sciences, School of Health Science and Nursing, Faculty of Medicine, The University, Japan; and 3Kumamoto Health Management Center, The Japanese Red Cross Company, Japan

Objective: The objectives were to examine the feasibility of using as a reference food in the study of glycemic index (GI) and to examine the GI values of both single and mixed meal foods among rice species, processed rice products, beans, and dairy products. Design: Subjects were served with 50 g carbohydrate content of white rice at least two times (maximum three times) and test food once after separate overnight fasts. Capillary blood glucose measurements were carried out before and during 120 min after each food load. Setting: The study was carried out in an outpatient setting. Subjects: A total of 58 (38 females and 20 males) nondiseased subjects, mean aged 37 y and mean BMI 22 kg/m2 were included. Result: The correlation between incremental area under curve of white rice and glucose was r ¼ 0.853 (n ¼ 10, Po0.0001) and white rice was considered suitable to be used as a reference food. Among mixed meal foods, the combination of carbohydrate foods with , dairy products, and bean products significantly decreased the GI value of white rice of 20–40%. The reduction of GI occurred whether the foods were taken together, before or after rice intake. GI of noodles such as , , and spaghetti showed low GI values. Conclusion: White rice could be used as a reference food in determining GI values of foods. A total of 32 single and mixed meal Japanese common food products were examined for their GI values. European Journal of Clinical Nutrition (2003) 57, 743–752. doi:10.1038/sj.ejcn.1601606

Keywords: glycemic index; rice; bean; dairy; vinegar; Japanese food

Introduction Brand Miller, 1995). Among published literature, most Jenkins (Jenkins et al, 1981) introduced the glycemic index studies were based in Western cultures and had used either (GI) in 1981 by comparing the postprandial blood glucose white bread or glucose as the reference foods. For most Asian incremental area under curve (IAUC) of different carbohy- population who consume white rice as a staple food, rice is drate foods. Since the introduction of the GI, numerous more readily available and is considered more palatable. For studies were conducted to test the GI of different foods and routine use, white rice used as a reference food would be an International GI Table was published (Foster-Powell & more convenient in these countries when compared to white bread. Therefore, it is necessary to consider the use of white rice as a reference food. In addition, studies conducted *Correspondence: M Sugiyama, Division of Applied Nutrition, Laboratory among Japanese population with the internationally of Nutrition Care and Management, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8636, Japan. adopted GI evaluation method have not been reported. As E-mail: [email protected] a result, limited items published in the literature can be Guarantor: M. Sugiyama. applied as common Japanese foods. Prior to the utilization Contributors: M Sugiyama provided the concept and design of the of the GI concept in Japanese research and clinical setting, it study. AC Tang carried out the literature research, data analyses and prepared the report. YW was responsible for data acquisition and is considered necessary to test the GI of commonly analyses. WK was also responsible for the data acquisition. consumed Japanese foods among the local population with GI of single and mixed Japanese meal foods M Sugiyama et al 744 white rice as a reference. The objectives of the current study Study protocol were to examine the feasibility of using white rice as a The experiment was based on the method by Wolever reference food and to test the GI of some common Japanese (Wolever et al, 1991). Groups of 9–11 subjects were derived food. from the total pool of 58 subjects to test for one food. All subjects took 50 g carbohydrate load of reference food (white rice) at least two times (maximum three times) and test food Method once on random days. A subject who took more than one test food had at least 2 days of wash-out period in between Subject food testing. Subjects started fasting from 09:00 on the A total of 58 healthy subjects (38 females and 20 males) who previous evening before examination. Meals were given to self-reported that they were not diagnosed with glucose the subjects from 07:00 to 09:00 on random days. Foods were intolerance or diabetes (based on their blood glucose consumed within 15 min. The subjects carried out self- and HbA examinations from the past 1 year) were 1c monitoring blood glucose measurement seven times in total: included. The demographic characteristics of the subjects at fast, and at 15, 30, 45, 60, 90, and 120 min after load. are shown in Table 1. These subjects had an average age of Capillary blood glucose measurement was performed using 37710 and BMI 2272.7 kg/m2 (mean7s.d.). In all 25 self-administered blood measuring device (Glutestase, Sanwa subjects had family history of diabetes, 11 subjects took Chemical Research Institute Co. Inc.). The reliability of the medication or supplements not related to glucose metabo- device was tested in another occasion by measuring the same lism. Informed consent was obtained from each of the blood sample for 30 times and the coefficient of variation subjects according to the requirements set by the ethics (CV) obtained was below 2.9. The correlation coefftcient of committee of the Japanese Red Cross Company, Kumamoto blood glucose value measured with self-administered blood Health Management Center, which conformed to the measuring device and the value measured using the glucose Helsinki Declaration. automatic analysis device (The First Co. Inc. Kyoto Science GA-1 140) was r ¼ 0.997 (n ¼ 62). Reference food The reference food was the aseptic packed Satou Rice, which was labeled to contain 34 g of carbohydrate per 100 g of rice. Calculation of the GI Each portion of the weighed 147 g and contained The GI was defined as follows (Wolever, 1990): 50 g of carbohydrate value. Incremental area under blood glucose response curve ðIAUCÞfor a food GI ¼ Â 100 Corresponding area after equicarbohydrate Test food portion of a reference food Test foods were chosen from common Japanese processed rice products, beans, and dairy foods. A total of 32 items were IAUC of each test food and mean IAUC for the initial two tested for their GI based on white rice as the reference food. reference foods were calculated for each person. When the Each test food contained 50 g of carbohydrate. In mixed percentage change of the initial two reference foods IAUC meals or combination meals, the total nutrition value was more than 25%, the subject took reference food the third summed up to approximately 50 g carbohydrate. For exam- time and mean IAUC of the closest two values was used as ple, for white rice and yogurt, 132 g of white rice (44.9 g of the reference. On the other hand, if the per cent change of carbohydrate) and 100 g of yogurt (5.3 g carbohydrate) were the two closest IAUC exceeded 25%, the subject would be given as one test food item. The reference food, test foods, excluded from the analysis. Mean GI and s.d. of each test nutrition component, and methods of offering foods are food was obtained from the remaining subjects in the group. shown in Table 2. Subjects who had GI exceeding 2s.d. were also excluded from

Table 1 Subject characteristics

Total (n=58) Male (n=20) Female (n=38)

Age (y) 37710 (22–66) 40711 (27–66) 3579 (22–53) BMI (kg/m2)2272.7 (17.1–28.4) 23.573.0 (18.5–28.4) 21.372.2 (17.1–27.1) Family diabetes history positive 25 4 21 Currently on Medication 11 2 9 Traditional medicine 4 1 3 Hormonal medication 3 1 2 Vitamin 3 F 3 Calcium supplement 1 F 1

European Journal of Clinical Nutrition Table 2 Nutrient component, amount, and method of preparation for the common Japanese foods used

Nutrition Value of Food Weight per Carbo- Produced by portion hydrate Energy Protein Fat Sodium Name of Food (Japanese Name) Ingredient and Food Form (Company Name) (g) (g) (kcal) (g) (g) (mg) Method of Preparationa

White rice-reference food Aseptic packed white rice Satou Co. Ltd 147.0 50.2 223.0 3.5 0.9 4.4 Sprinkle algae on rice and warm (beihan) Dried sea algae Mishima Shokuhin 1.0 0.2 1.0 0.1 0.0 210.0 Serve in form of rice ball (onigiri) Dried sea algae () Total 50.4 224.0 3.6 0.9 214.4 1. Rice gruel Aseptic packed rice gruel Satou Co. Ltd 658.0 50.2 244.5 5.4 1.3 223.2 Mix dried algae in rice gruel and warm (okayu) Mishima Shokuhin 1.0 Serve with drink 2. Salted rice ball Aseptic packed white rice Satou Co. Ltd 147.0 50.0 222.0 3.4 0.9 Warm rice and sprinkle with (shiomusubi) Salt 3–5 1974.4–1954.4 Serve with drink 3. Roasted Rice ball Aseptic packed white rice Satou Co. Ltd 140.0 50.1 225.5 4.5 0.7 567.0 Warm roasted rice (yakionigiri) Serve with drink 4. Vinegared rice Aseptice packed white rice Satou Co. Ltd 136.0 46.2 205.4 3.1 0.8 4.1 Warm rice and mixed with vinegar () Vinegar Mitsukan 11.0 3.9 17.1 0.0 0.0 273.8 Roll with toasted algae when cool Roasted sea algae 1.0 0.4 0.0 0.4 0.0 1.3 Serve with drink Total 50.6 222.5 3.5 0.8 279.2 5. Rice cracker Rice cracker Sakada 25 pieces 50.0 275.0 4.6 6.1 320.0 25 pieces of rice cracker (osenbe) 6. Nonglutaminous rice flour Rice cake Yamato Nousan 100.0 50.2 221.0 1.9 0.3 5.0 Warm and serve with drink (shin-kona ) 7. Aseptic packed white rice Esubi Shokuhin 116.0 49.9 224.5 4.3 0.8 181.0 Warm rice (sekihan) Serve in form of rice ball (onigiri) with drink 8. Glutaminous rice flour Instant rice flour Satou Co. Ltd 117.0 48.4 220.0 4.4 0.9 7 Warm glutaminous flour (shiratama) Roasted and ground soybean Mitake Shokuhin 5.0 11.7 22.1 1.8 1.1 0.0 Cover with ground soybean Total 50.1 242.1 6.2 2.1 7.0

9. Glutinous rice cake Cut glutinous rice cake Satou Co. Ltd 97.0 50.2 224.1 4.1 0.8 1.9 Serve warm with dried algae and drink foods meal Japanese Sugiyama mixed M and single of GI (mochi) Dried sea algae Mishima Shokuhin 1.0 0.2 1.0 0.1 0.0 210.0 Total 50.4 225.1 4.2 0.8 211.9 10. Glutinous rice ball Cut glutinous cake (mochi) Satou Co. Ltd 50.0 25.9 115.5 2.1 0.4 1.0 Warm ingredient and serve

(oshiruko) Glutinous rice ball Nishin Seifun 82.0 24.1 112.8 2.1 0.5 40.5 al et Total 50.0 228.3 4.2 0.9 41.5 11. Low protein white rice Aseptic packed white rice Satou Co. Ltd 124.0 50.2 220.5 1.5 0.4 212.6 Warm and seve with dried algae and drink (tei-tanpaku gohan) Dried sea algae Mishimi Shokuhin 1.0 0.2 1.0 0.1 0.0 210.0 Total 50.4 221.5 1.6 0.4 422.6 12. White rice and sated Aseptic packed white rice Satou Co. Ltd 142.0 49.9 221.3 3.3 0.9 294.3 Warm rice and serve with salted plum plum frout () Salted plum Pickles Corporation 10.0 1.6 6.9 0.1 0.0 290.0 Total 49.9 221.3 3.3 0.9 294.3 13. White rice and dried Aseptic packed Satou Co. Ltd 147.0 50.2 223.0 3.5 0.9 4.4 Warm rice fish strip white rice (okaka) Fish strip (katsuo) 1.0 0.0 3.6 0.8 0.0 1.3 Fish strip mixed in and top on rice Soy sauce Kikkoman 2.0 0.1 1.2 0.2 F 118.0 Total 50.3 227.8 4.5 0.9 123.7 14. White rice rolled in Aseptic packed white rice Satou Co. Ltd 144.0 49.0 217.4 3.3 0.9 4.3 Warm rice, sprinkle with dried algae uoenJunlo lnclNutrition Clinical of Journal European toasted algae Sea algae Nihon Nousuisan 2.0 0.8 F 0.8 0.0 2.6 Roll in algae sheet ( gohan) Dried sea algae Mishima Food 1.0 0.2 1.0 0.1 0.0 210.0 Total 50.0 218.4 4.2 0.9 216.9 15. White rice and egg Aseptic packed white rice Satou Co. Ltd 146.0 45.6 220.0 3.4 0.9 4.4 Warm rice topped with raw egg (tamagokake gohan) Raw egg 60.0 0.5 97.2 7.4 6.7 78.0 Soy sauce Kikkoman 2.0 0.1 1.2 0.2 F 118.0 Total 50.2 317.7 10.7 7.6 82.4 16. Curry rice Aseptic packed white rice Satou Co. Ltd 124.0 42.2 187.2 2.9 0.7 3.7 Warm rice and top with warm curry Packed curry House Food 100.0 7.9 91.9 2.9 5.4 438.1 Total 50.1 279.1 5.8 6.2 441.8 745 746 uoenJunlo lnclNutrition Clinical of Journal European

Table 2 (Continued)

Nutrition Value of Food Weight per Carbo- Produced by portion hydrate Energy Protein Fat Sodium Name of Food (Japanese Name) Ingredient and Food Form (Company Name) (g) (g) (kcal) (g) (g) (mg) Method of Preparationa

17. White rice and pickled Aseptic packed white rice Satou Co. Ltd 138.0 46.9 208.4 3.2 0.8 4.1 Slice cucumber and mix with vinegar food (beihan, sunomono) Vinegar Mitsukan 15.0 2.6 12.0 0.2 0.0 200.0 Serve with warm rice Cucumber 20.0 0.3 2.2 0.2 0.0 0.4

Total 49.8 222.6 3.6 0.9 204.5 foods meal Japanese mixed and single of GI 18. White rice and milk Aseptic packed white rice Satou Co. Ltd 118.0 40.12 178.18 2.714 0.71 3.54 Sprinkle algae on warm rice Dried sea algae Mishima Shokuhin 1.0 0.2 1.0 0.1 0.0 210.0 Serve in form of rice ball Milk Snow Brand 100.0 9.7 138.0 6.6 8.0 103.0 Serve with milk Total 50.0 317.2 9.4 8.7 316.5 19. White rice and low fat milk Aseptic packed white rice Satou Co. Ltd 119.0 40.5 179.7 2.7 0.7 3.6 Warm rice and serve with milk Processed milk Kenrakuren 170.0 9.7 83.3 6.5 1.7 102.0 Total 50.2 263.0 9.2 2.4 105.6 20. Butter rice Aseptic packed white rice Satou Co. Ltd 147.0 50.0 222.0 3.4 0.9 4.4 Warm rice and butter Butter Snow Brand 10.0 0.0 73.2 0.1 8.1 55.0

Total 50.0 295.2 3.5 9.0 59.4 Sugiyama M 21. White rice and yogurt Aseptic packed white rice Satou Co. Ltd 132.0 44.9 199.3 3.0 0.8 4.0 Pickle food serve with, immediately before, or immediately after Nonsugar yogurt Meiji Dairy 100.0 5.3 62.0 3.4 3.0 51.0 warm rice

Total 50.2 261.3 6.4 3.8 55.0 al et 22. White rice and ice-cream Aseptic packed white rice Satou Co. Ltd 72.0 24.5 108.7 1.7 0.4 2.2 Ice-cream taken after rice consumption Ice-cream Meiji Dairy 120.0 25.4 262.8 3.7 16.3 62.4 Total 49.9 371.5 5.4 16.8 64.6 23. White rice with curry and Aseptic packed white rice Satou Co. Ltd 119.0 40.5 179.7 2.7 0.7 3.6 Warm rice and serve with cheese and curry cheese Processed cheese Morinaga Dairy 36.0 0.4 114.0 7.6 9.0 266.0 toppings Packed curry House Food 100.0 9.3 211.0 5.5 12.3 880.0 Total 50.1 504.7 15.8 22.0 1149.6 24. White rice and Aseptic packed white rice Satou Co. Ltd 127.0 43.2 191.8 2.9 0.8 3.8 Warm rice mixed in roasted and roasted, ground soybean ground soybean (beihan, kinako) Roasted and ground soybean Mitake Food Ind. 20.0 6.8 88.4 7.1 4.5 0.1 Total 50.0 280.2 10.0 5.3 3.9 25. White rice and Aseptic packed white rice Satou Co. Ltd 144.0 49.0 217.4 3.3 0.9 4.3 Fermented soybean served on top of fermented soybean (natto) warm rice Fermented soy bean Marukin Food 30.0 0.9 50.0 5.2 2.8 123.0 Total 49.9 267.4 8.5 3.7 127.3 26. Soybean paste soup Aseptic packed white rice Satou Co. Ltd 138.0 46.9 208.4 3.2 0.8 4.1 Warm rice ( shiru) and rice Instant 22.0 3.2 36.0 2.2 0.9 728.0 Instant soy paste mixed in 200 cm3 (soybean soup) of hot water Total 50.1 244.4 5.4 1.7 732.1 27. Glucose solution Solution for glucose Shimuzu Pharm. 150.0 50.0 200.0 0.0 0.0 0.0 Measure portion and serve tolerance test 28. Bread Flour Nishin Shokuhin 70.3 48.5 239 8.4 1.3 0 Mix total ingredient for all members International standard for Sugar Nishin Shokuhin 1.5 1.5 5.8 0.0 0.0 0.0 Measure dough before baking reference foodFwhite bread Salt Nishin Shokuhin 0.9 0.0 0.0 0.0 0.0 331.5 Divide dough into portion per person and bake Yeast Nishin Shokuhin 1.1 0.1 0.9 0.1 0.0 0.2 Bread serve with drink Water 42.2 0.0 0.0 0.0 0.0 0.0 Total 50.1 245.7 8.6 1.3 331.7 29. Corn flake and milk Corn flake Ajinomoto 45.0 40.3 168.8 2.5 0.1 313.9 Serve corn flake with milk Milk Snow Brand 200.0 9.7 138.0 6.6 8.0 103.0 Total 50.0 306.8 9.1 8.1 416.9 GI of single and mixed Japanese meal foods M Sugiyama et al 747 the group and a final mean GI was recalculated to give each test food a GI.

Validity of the reference food and the conversion factor

a To examine the feasibility of using white rice as a reference food, white rice was compared with 50 g pure glucose (150 g of glucose-tolerance-test glucose solution; Shimizu Seiyaku). of soup 3 Similar to the protocol stated above, subjects took white rice at least two times and glucose solution once. The mean IAUC of white rice and the IAUC of glucose were compared among cut accordingly Serve with measured soup Method of Preparation a group of 10 subjects. Correlation coefficient of the two IAUC was determined. To allow comparisons across different studies based on glucose or white rice as a reference, a ) conversion factor to adjust the glucose-based GI (GIg) of any mg ( Sodium test food to white-rice-based GI (GIwr) and vice versa was determined. For the white-rice-based GI to glucose-based GI

conversion factor, it was calculated as: l00/(mean GIg WR),

) where mean GI WR represents the mean glucose-based GI of

Fat g g ( white rice of the 10 subjects. GIg WR of each subject was calculated as (mean incremental area of white rice/incre- ) g

( mental area of glucose) Â 100. Protein

Nutrition Value of Food Statistical analysis ) Statistical analysis was performed using the SPSS program kcal ( Energy (Version 9.0). The correlation coefficient was analyzed using Pearson’s correlation coefficient. The significance of differ- )

g ence between reference and test food was tested by one ( Carbo- hydrate sample t-test of the mean. Repeated measurements two-way ANOVA was used to assess heterogeneity in glucose response between foods. Data were shown as mean values7s.d., ) g Total 50.0Total 260.5 50.2 7.8 294.1 3.2 9.4 2292.0 6.2 1002.1 ( per unless otherwise stated. Po0.05 was considered significant. Weight portion

Result The correlation between IAUC of rice and glucose was r ¼ 0. 853 (n ¼ 10, Po0.002) (Figure 1). The high correlation indicated that using rice as a reference food would be

possible. White-rice-based GI (GIwr) was higher than glucose- Nishin Shokuhin 27.0 Measure fried bean curd and Produced by (Company Name) based GI (GIg by a factor of 100/GIg WR ¼ 100/80 ¼ 1.2, where 100 is the GI of glucose and 80 is the GIg of white rice or water; to warm means to warm in a microwave oven.

3 (Table 3). Comparison of the white-rice-based study with other glucose-based studies could be done by proportio- nately adjusting the glucose-based GI to white-rice-based GI by a factor of 1.2, and vice versa by a factor of 0.8, so that the adjusted reference value is ascribed to be 100. The results of 32 Japanese foods are listed in Table 4. Among single and mixed meals of common Japanese foods, Cooking oil (4 g)Sauce (9 g) Nishin Shokuhin Nishin Shokuhin 3.0 7.0 Mix in oil and sause Serve with drink Flavored fried dry bean curd (35 g) Sauce (15 g) Nishin Shokuhin 11.0vinegar products, dairy products, and Use 230 cm bean products reduce the GI of rice when consumed together. For example, the use of vinegar in rice (sushi, GI ¼ 67) and vinegar-pickled foods (GI ¼ 75–77) decrease the GI of rice by about 20–35%. Dairy

) products also had low GI and GI-lowering effect. When white rice was taken with 100 ml of milk, the GI of rice was significantly reduced to 59. The intake of milk immediately Continued ( before or after rice both significantly reduced the GI of rice to 67 and 68, respectively. The intake of yogurt before or after Served with drink means the food is served with 150 cm 31. Spaghetti32. Soba (noodle) Instant raw type (170 g) Instant packed noodle Nishin Shokuhin Sugakiya Shokuhin 121.0 185.0 49.9 364.3 11.1 13.3 2.7 Measure noodle and warm in hot water Measure noodle and boil in hot water 30. Noodle (Udon) Instant raw type (200 g) Nishin Shokuhina 153.0 Measure noodle and boil in hot water Table 2 Name of Food (Japanese Name) Ingredient and Food Form rice also significantly reduced the GI of rice. The significant

European Journal of Clinical Nutrition GI of single and mixed Japanese meal foods M Sugiyama et al 748

Figure 1 Correlation between IAUC of white rice and IAUC of glucose.

GI lowering effect of bean and bean products (fermented other grain products constitute for only about 12% of the soybean, GI ¼ 68; roasted and grounded soybean, GI ¼ 68; total energy consumed per day. A common Japanese meal bean paste soup, GI ¼ 74) were also observed. Significant usually consists of white rice with a main dish (protein-rich difference between IAUC of the reference food and the test foods such as fish, meat, bean, or bean products) and one or food were seen for dairy products, bean products, udon, and two side-dishes (vegetables, sea algae, milk, or milk products, spaghetti. etc). GI study based on such meal structure is important in Japan and probably in other Asian cultures that consume rice as the staple food as well. In the previous studies, glucose and white bread were commonly used as reference foods for Discussion calculating GI. It was reported that white-bread-based GI In the current study, Japanese staple food, white rice was were higher than glucose-based GI by a factor of 1.42 (GI of examined for its feasibility as a reference food. In addition, white bread ¼ 70; Glucose ¼ l00), and that the white-bread- using the International GI determination method, single based GI was adjusted to glucose-based GI by 0.7 (Foster- and mixed meals of white rice, processed rice products, Powell & Brand Miller, 1995). White bread was used instead beans, and dairy products were compared for their incre- of glucose as a reference food because it was considered more mental area under blood glucose curves and the GI of each palatable and was thought to correlate to insulin secretion food product was evaluated based on white rice as the better than glucose (Bornet et al, 1987; Wolever et al, 1988). reference food. The results showed that IAUC of white rice However, for most Asian population who consume white rice and glucose had high correlation and, therefore, was as a staple food, white bread as a reference food is considered considered suitable to be used as a reference food. Moreover, less applicable for a number of reasons. First of all, white rice it was determined that white-rice-based GI was higher than is more conveniently available than white bread. If white glucose-based GI by a factor of 1.2. And, white-rice-based GI bread is to be used as a reference food, it must be baked could be adjusted to glucose-based GI by a factor of 0.8. In according to the standard method each time a food is tested determining the GI of mixed meal foods, vinegar, dairy for its GI. Such test protocol can be difficult to achieve. Since products, and bean products had GI lowering effect when white rice is readily available and can be easily prepared, it is consumed with rice. easier for standardization. Secondly, flour used in Japan may White rice is the staple food in Japan. It is a self-sufficient originate from different wheat specie and when used for grain product and is considered a cultural food. According to bread, the result would not be comparable to the results the Japanese National Nutrition Survey (Department of published in other countries. Thirdly, just as white bread is Health Promotion and Nutrition, The Ministry of Health, more palatable in Western countries, white rice is considered 1996), the average consumption of white rice is 161 g/day/ more palatable among the Japanese population. Lastly, in person and rice is consumed two times or more per day. Rice studying Japanese mixed meal and added ingredients on the accounts for about 29% of the total energy consumed by an effect of GI, it is more ‘consumer-friendly’ to use the adult and constitutes for 14% of the total protein energy commonly consumed white rice as a reference and compare consumed per day. On the other hand, total energy from other Japanese foods with it. For these reasons, examining

European Journal of Clinical Nutrition GI of single and mixed Japanese meal foods M Sugiyama et al 749 Table 3 Comparison of the incremental areas and GI between white rice and glucose

a Subject Sex Age Mean white rice IAUC Glucose IAUC GIg of WR

Subject A F 46 3023.0 2872.5 105 Subject B F 26 4717.5 5977.5 79 Subject C F 40 4432.5 4702.5 94 Subject D F 36 3851.3 4906.3 78 Subject E F 40 2598.8 3165.0 82 Subject F F 26 3693.8 4342.5 85 Subject G F 43 5419.0 7845.0 69 Subject H F 25 3806.3 5400.0 70 Subject I F 26 2312.1 3862.5 60 Subject J M 38 3273.8 2500.4 131

Mean 34.6 3712.8 4557.4 80b a Glucose-based glycemic indices (GIg), where GIg of WR=WR/G Â 100. bn=9 after excluding ‘Subject J’ who has GI exceeding 2s.d. of the total mean. white rice as a reference food was thought to be of good taken with, before or after rice ingestion. In addition, when significance. cheese was added to curry, the GI also decreased. Fat and Rice of other species and processed rice products are protein in the dairy products were probably responsible for common foods in Japan. Among the European and American the GI lowering effect by lengthening the gastric emptying countries, observations of GI values using different rice and absorption process (Collier & O’Dea, 1983). Although species and processed rice (steamed, boiled, stir-) dairy products seem to be low in GI and has a GI lowering have been reported (Foster-Powell & Brand Miller, 1995). The effect in general, it has been criticized that these foods results showed that rice tested among diabetics and non- caused excessive secretion of insulin (Liljeberg & Bjorck, diabetics varied from GI ¼ 38 to 94 (Glucose ¼ l00). The great 2001). Insulin response was not measured in the current difference in GI of rice was because of a number of reasons. study and it was impossible for us to deduce the insulin Studies have reported that the variation of species (Miller response of the dairy products as well as other food products. et al, 1992), process condition (Brand et al, 1985, Traianedes Nevertheless, future study should consider the measurement & O’Dea, 1986), food structure such as particle size and of insulin in addition to glycemic response. With the shape (Jar-vi et al, 1994; Behall et al, 2000), starch content excessive insulin response of some foods, careful selection such as amylose vs amylopectin (Behall et al, 1989; Panlasigui of low GI foods should be taken to meet individual needs. et al, 1991) would change the GI of foods significantly. In the current study, the addition of vinegar and vinegared Amylose content in starch has an effect on the GI where low- foods to white rice reduced the GI of white rice. The acetic amylose rice and instant rice were reported to have a higher acid in vinegar was thought to be responsible for the

GIg (mean GI ¼ 88–91), while (mean GIg ¼ 47), antihyperglycemic effect. The amount of acetic acid to be (mean GIg ¼ 55) and long-grain white rice effective could be as low as that found in sushi (estimated to (GIg ¼ 56) had a lower GI. The species of rice used for the be about 0.2–1.5 g/100 g). The antihyperglycemic effect of reference food and for the test foods in the current study was vinegar is consistent with other studies performed the Koshihikari, a species favored by most Japanese. It is earlier (Brighenti et al, 1995; Liljeberg & Bjorck, 1998). known to have a relatively low-amylose content (17% Although vinegar could lower GI vales, the mechanism has amylose). The GIg of white rice was 80, which was similar rarely been reported. Most studies accounted the mechanism to the results of low-amylose white rice published in other to be due to a delay in gastric emptying. In animal studies, countries. Glutinous rice in our study showed GI higher than Fushimi (Fushimi et al, 2001) showed that acetic acid could that of white rice. We deduced that it was because of the very activate gluconeogenesis and induce glycogenesis in the liver low-amylose content of the specie. after a fasting state. It could also inhibit glycolysis in In the current study, it was found that dairy products muscles. The mechanism of vinegar is yet to be confirmed significantly reduced the GI of white rice when consumed with further studies in such respect. together, prior to or after a carbohydrate meal. The results Bean and bean products that were tested in the current are consistent with previous studies where dairy products study showed low GI values and had GI lowering effect when decreased the GI of foods. Among previous studies, the GI of consumed with a carbohydrate meal. Previous studies corn flake alone was classified as a high GI food but when showed that beans, lentils, and legumes had low GI values. milk was added to corn flake, the GI decreased (Miller et al, The mechanism of the low GI of these food products seem to 1998). Similarly, in our study, milk and yogurt, both, caused be because of the soluble fiber, antinutrients available in the the GI of rice to decrease, whether the dairy products were foods (Wolever & Bourne, 1990).

European Journal of Clinical Nutrition GI of single and mixed Japanese meal foods M Sugiyama et al 750 Table 4 Glycemic index of the common Japanese foods

GI

Food name n Mean7s.d. (Min–Max) Pa Pb

Reference food 100 White rice

Rice and other processed rice 1. Rice gruel 10 99738 (28–149) 2. Salted rice ball 7 97729 (59–154) 3. Roasted rice ball 9 94722 (63–133) + 4. Sushi 8 67714 (47–84) *** 5. Rice cracker 10 111744 (39–184) 6. Non-glutinous rice flour 8 83720 (49–107) * 7. Glutinous rice 6 105720 (84–134) 8. Glutinous rice flour 9 79724 (42–114) * ++ 9. Glutinous rice cake 8 101718 (77–133) 10. Glutinous rice ball 9 58718 (35–91) *** + 11. Low protein white rice 10 86728 (39–123)

Rice and other mixed meals 12. White rice and salted plum frouts 10 98749 (46–175) 13. White rice and dried fish strip 6 115743 (47–182) 14. White rice rolled in toasted algae 7 94755 (40–196) 15. White rice with raw egg 6 114750 (50–160) 16. White 10 82733 (33–133) 17. White rice and pickled food (taken before rice) 9 73729 (36–118) (Taken with rice) 11 75725 (41–107) +

Rice and dairy products 18. Milk 100 ml(taken together) 9 59728 (10–94) ** + (Taken after rice) 9 68727 (34–109) ** ++ (Taken before rice) 9 67714 (47–84) *** +++ 19. White rice and low fat milk 9 84735 (38–151) + 20. Butter rice 10 96748 (46–178) 21. White rice and yogurt (taken before rice) 10 72728 (29–111) * ++ (Taken after rice) 10 71724 (39–107) ** +++ 22. White rice and ice-cream 9 57722 (23–89) *** ++ 23. White rice and curry rice with cheese 10 67734 (10–127) * ++

Rice and bean products 24. White rice and roasted, grounded soybean 9 68715 (44–89) *** + 25. White rice and fermented soybean (natto) 10 68730 (30–114) ** 26. White rice with miso (soybean paste) soup 10 74717 (54–99) *** +

Other carbohydrate Foods 27. Glucose solution 10 122726 (76–167) * 28. White bread 10 92738 (37–146) 29. Cornflake and milk 6 68716 (46–92) ** 30. Udon (noodle) 9 58719 (26–83) *** ++ 31. Spaghetti 10 56737 (24–109) ** +++ 32. Soba (noodle) 9 56734 (44–75) ***

PaSignificant difference of GI between test food and the reference food (white rice with GI=100); *Po0.05, **Po0.01, ***Pb Shows significant difference in blood glucose response between test food and reference food (white rice) analyzed by repeated measure ANOVA; +Po0.05, ++Po0.01, +++Po0.00l.

The GI of spaghetti showed similar result with previous In the current study, white bread showed GI ¼ 92 that studies and the GI of (udon and soba) were coverts to GI ¼ 110 (92 Â 1.2) when Glucose ¼ 100. In other almost identical to spaghetti showing significant lower GI studies, where white bread was tested, it had an average GI of than white rice. It has been reported that structural proper- about 70 when Glucose ¼ 100 (Foster-Powll & Brand Miller, ties would affect the glycemic response of pasta (Katri et al, 1995). Bread used for current testing was baked according to 2002). Thus, udon, soba, and spaghetti may have similar GI the published standard method. It is difficult to explain the values because of their similar structural properties. large difference between these results. However, the differ-

European Journal of Clinical Nutrition GI of single and mixed Japanese meal foods M Sugiyama et al 751 ence in specie between Japanese-produced flour and Eur- Brand Miller JC (1994): Importance of glycemic index in diabetes. opean/American-produced flour could be a possible factor Am. J. Clin. Nutr. 59, 747S–752S. that caused the difference. The variety in results gave a good Brighenti F, Castellani G, Benini L, Casiraghi MC, Leopardi E, Crovetti R & Testolin G (1995): Effect of neutralized and native reason for us to use a different reference food other than vinegar on blood glucose and acetate responses to a mixed meal in bread for GI testing in Japan. healthy subjects. Eur. J. Clin. Nutr. 49, 242–247. Numerous food studies as well as intervention studies have Collier G & O’Dea K (1983): The effect of coingestion of fat on the been conducted over the past decade to examine the benefits glucose, insulin, and gastric inhibitory polypeptide responses to carbohydrate and protein. Am. J. Clin. Nutr. 37, 94l–944. of low GI diets. Among most studies, low GI diets were Department of Health Promotion and Nutrition, The Ministry of reported to have positive effect in blood glucose control Health (1996): The 1994 Japanese National Nutrition Survey. among diabetes patients (Fontvieille et al, 1992; Wolever et al, Daichi Publishing. 1992; Brand Miller, 1994; Salmeron et al, 1997; Jenkins et al, Fontvieille AM, Rizkalla SW, Acosta M, Bornet FR & Slama G (1992): The use of low glycaemic index foods improves metabolic control 1998; Jar-vi et al, 1999; Luscombe et al, 1999) and in blood of diabetic patients over five weeks. Diabetic Med. 9, 444–450. lipid lowering effect (Jenkins et al, 1987). Since white rice is a Foster-Powell & Brand Miller J (1995): International tables of major high GI carbohydrate source, understanding the glycemic index. Am. J. Clin. Nutr. 62, 871S–893S. general diet structure among the rice-dominant populations Fushimi T, Tayama K, Fukaya M, Kitakoshi K, Nakai N, Tsukamoto Y is necessary. Moreover, efforts to select combinations of & Sato Y (2001): Acetic acid feeding enhances glycogen repletion in liver and skeletal muscle of rats. J. Nutr. 131, 1973– carbohydrate foods that could reduce postprandial glucose 1977. response could contribute to preventive and clinical health Jarvi AE, Kalstrom BE, Granfeldt YE, Bjorck IE, Asp NG & Vessby BO care. The current study should serve as an important (1999): Improved glycemic control and lipid profile and normal- reference in the future when using GI as a tool for diet ized fibrinolytic activity on a low-glycemic index diet in type 2 diabetic patients (1999). Diabetes Care 22, 10–18. education not only among Japanese population but also Jarvi A, Karlstrom B, Granfeldt Y, Bjorck I, Vessby B & Asp NG (1994): other Asian population, who consume rice as a staple food The influence of food structure on postprandial metabolism in and have similar meal structure. In conclusion, white rice patients with non-insulin-dependent diabetes mellitus. Am. J. can be used as the reference food in determining GI of Clin. Nutr. 59, 794S. various Japanese foods. Among common Japanese foods, Jenkins DJA, Wolever TMS, Buckley G, LamKy, Giudici S, Kalmusky J, Jenkins AL, Patten RL, Bird J, Wong GS & Josse RG (1998): Low- vinegar, dairy products, and bean products significantly glycemic-index starchy foods in the diabetic diet. Am. J. Clin. Nutr. decreased the GI of rice when ingested together, before, or 48, 248–254. after meal. Jenkins D, Wolever T & Kalmusky J (1987): Low-glycemic index diet in hyperlipidemia: use of traditional starchy foods. Am. J. Clin. Nutr. 46, 66–71. Jenkins DJA, Wolever TMS, Taylor RH, Barker H, Hasemein F, Baldwin JM, Bowling AC, Newman HC, Henkins AL & Goff DV (1981): Acknowledgements Glycemic index of foods: a physiological basis for carbohydrate We thank the staff from the Japanese Red Cross Kumamoto exchange. Am. J. Clin. Nutr. 34, 184–190. Health Care Center and the staff from the Hospital Katri SJ, Leo KN, Kirsi HL, Kaisa SP, Jens JH & Hannu MM (2002): Postprandial glucose, insulin, and incretin responses Management Department, the National Institute of Health to grain products in healthy subjects. Am. J. Clin. Nutr. 75, and Nutrition for their support and assistance. Also, we 254–262. thank Dr N Hosoya (Professor Emeritus, the Tokyo Liljeberg EH & Bjorck I (2001): Milk as a supplement to mixed meals University) for his invaluable advice to the research. The may elevate postprandial insulinaemia. Eur. J. Clin. Nutr. 55, 994– 999. research was funded by the National Rice Association and Liljeberg H & Bjorck I (1998): Delayed gastric emptying rate may the National Daily Promotion and Research Association of explain improved glycaemia in healthy subjects to a starchy meal Japan. with added vinegar. Eur. J. Clin. Nutr. 52, 368–371. Luscombe ND, Noakes M & Clifton PM (1999): Diets high and low in glycemic index versus high monounsaturated fat diets: effects on glucose and lipid metabolism in NIDDM. Eur. J. Clin Nutr. 53, References 473–478. Behall KM, Scholfield DJ & Hallfrisch J (2000): The effect of particle Miller JB, Pang E & Bramall (1992): RiceFa high or low glycemic size of whole grain flour on plasma glucose, insulin and TSH in index food? Am. J. Clin. Nutr. 56, 1034–1036. human subjects. J. Am. Coll. Nutr. 18, 591–597. Miller JB, Wolever TMS, Colagiuri S & Power KFB (1998): The Glucose Behall KM, Scholfield DJ, Yuhaniak I & Canary J (1989): Diets Revolution. New York: Marlowe & Company, pp. 239–254. containing high amylose vs amylopectin starch: effects on Panlasigui LN, Thompson LU, Juliano BO, Perez CM, Yiu SH & metabolic variables in human subjects. Am. J. Clin. Nutr. 49, Greenberg GI (1991): Rice varieties with similar amylose content 337–344. differ in starch digestibility and glycemic response in humans. Am. Bornet FRJ, Costagliola D, Rizkalla SW, Blayo A, Fontvieille AM, J. Clin. Nutr. 54, 87l–877. Haardt MJ, Letanoux M, Tchobroutsky G & Slama G (1987): Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing Al & Insulinemic and glycemic indexes of six starch-rich foods taken Willett WC (1997): Dietary fiber, glycemic load, and risk of alone and in a mixed meal by type 2 diabetics. Am. J. Clin. Nutr. 45, non-insulin-dependent diabetes mellitus in women. JAMA 277, 588–595. 472–477. 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