The subjects selected for this clinical trial were healthy Korean volunteers who satisfied all the selection criteria: 1) male aged 20 to 40 years, 2) body weight is 50 kg or more and whithin 30% of their ideal body weight {ideal body weight = (height [cm] - 100) × 0.9}, and 3) agreement of study enrollment. Informed consent was obtained from each subject. Exclusion criteria include the following: 1) individuals with illness of the liver, kidneys, nervous system, respiratory, endocrine, blood, tumors, mental illness, or a history of cardiovascular disease, 2) individuals with a history of gastrointestinal diseases (e.g., Crohn's disease) that can influence nutrient absorption, gastrointestinal surgery (excluding simple appendectomy or hernia surgery), 3) blood test findings aspartate transaminase (AST)/alanine transaminase (ALT) > 1.25 times the upper limit of the normal range, 4) individuals having a systolic blood pressure under 100 mm Hg and over 150 mm Hg, or individuals having a diastolic blood pressure under 65 mm Hg and over 95 mm Hg, 5) individuals with hypersensitivity to experimental diets or having a medical history of clinical allergic reactions, 6) individuals who took prescribed drugs or eastern medicines two weeks before the beginning of the study, or individuals who took over-the-counter (OTC) medication or vitamin supplements (However, candidates may be able to participate at the discretion of the examinees), 7) individuals who have participated in other clinical trials two months prior to the beginning of this study, 8) individuals who have donated blood up to one month prior to the study, or individuals who have donated plasma within the two weeks prior to the beginning of the study, 9) individuals who drink 21 drinks/week or individuals who cannot abstain from alcohol consumption or more during clinical trials. For any other reason that the examiner thought that participants' participation would be irrelevant. A 4 × 4 cross-examination was carried out on a total of 32 patients. Statistical administration occurred in groups of eight.

The study was performed in open-label, 4-treatment, 4-order, 4-time frame crossover design (Table 1); appropriate candidates were selected through an interview, physical exam, and disease screening 4 weeks (D-28 to D-1) prior to the clinical trial and a random assignment was carried out one day prior (D-1) to the first day of the study.

For the first period of clinical trial (period 1), study subjects were admitted to the Clinical Trial Center for Functional Foods in Chonbuk National University Hospital by 7:00 PM on the 1st day. The subjects fasted with the exception of drinking water after the initial dinner that was provided by the center. At approximately 9:00 AM on the 2nd day, all the subjects who had been fasting consumed a control diet based on their randomly assigned group. A control diet was composed of the same amount of glucose with the carbohydrate content in corresponding test meal. Caloric and nutritional composition of each test meal is as follows: Korean 1 (Bibimbap) 588 kcal (carbohydrates 86.1 g, protein 24.6 g, and fat 16.53 g), Korean 2 (Kimbap) 598.7 kcal (carbohydrates 83.1 g, protein 27.6 g, and fat 17.14 g), Western 1 (pork cutlet) 602.2 kcal (carbohydrates 66.4 g, protein 28.4 g, and fat 23.2 g), Western 2 (hamburger) 586 kcal (carbohydrates 63.2 g, protein 30.6 g, and fat 23.2 g). The ingredients of the test meal were produced in the same region to ensure the consistency of the quality. They were also stored for a minimal amount of time within the expiration date. The cooking methods were also kept consistent by establishing a standard method for meal preparation regarding intensity of the cooking fire and cooking time. This standard was used for each preparation. The study subjects consumed the provided control diet within 2 minutes.

They were prohibited from consuming anything besides water after dinner on the 2nd day and provided the test meal on 9 AM in the next morning according to the group. The menu of each test meal was designed to include representative dishes for common types of cuisine: Korean 1 (Bibimbap), Korean 2 (Kimbap), Western 1 (pork cutlet), and Western 2 (hamburger) (the study subjects were instructed to consume the test meal within 15 minutes). After the end of the period 1, all the subjects were discharged and 6-day's resting period was followed by the period 2. For the period 2, subjects were admitted again and provied the control diet and test meal according to the same method in period 1. Period 3 and 4 were carried out in sequence with intervening 6-day's resting period.

The self-monitoring of blood glucose unit used for continuous blood glucose measurement needed for the study was a CGMS model from Medtronic (Northridge, CA, USA). Data was collected by inserting the blood sugar sensor under the skin using plasma calibration with an auto biochemistry machine (Hitachi 7600-11; Hitachi, Tokyo, Japan) which was measured and analyzed using the hexokinase method. For this process, blood glucose measurements were taken 4 times a day and inputted into the CGMS. Continuous blood glucose measurements were taken on day one (and on the 2nd, 8th, 9th, 15th, 16th, 22nd, 23rd day) between hour 0 (before the meal) and hour 4 every 5 minutes. Blood samples for measurement of blood glucose and insulin was taken on day one (and 2nd, 8th, 9th, 15th, 16th, 22nd, 23rd day) at hour 0 (before the meal), hour 0.25, hour 0.5, hour 0.75, hour 1, hour 2, and hour 4. A blood sample of 1 mL was taken from brachial veins without the use of a catheter due to the characteristics of the research methods.

Statistical analysis was performed using the following methods using a significance level of 0.05 (average ± standard deviation) with SPSS (SPSS Inc., Chicago, IL, USA), SAS (SAS Institute, Cary, NC, USA) and/or S-plus (TIBCO, Palo Alto, CA, USA) statistical software. Demographic statistical analysis of participants of the clinical trial was carried out to ensure random sampling. Participant age, height, body weight, and alcohol and caffeine consumption information was collected for demographic statistical analysis.

Analysis of variance (ANOVA) was used for continuous variables, and Fisher's exact test was used for categorical variables. The correlation and significance between the glucose level measured from the reference sample of venous blood, and that from CGMS were analyzed using linear regression analysis.

Each measured level was marked as a distribution point using a Clarke error grid analysis; areas A and B are clinically acceptable regions and areas C, D, and E are regions which are considered unsafe or unacceptable.

Thirty-two adult males were randomly assigned to participate in this study. Mean age was 23.9 ± 1.5 years, mean height was 173.9 ± 5.3 cm, mean body weight was 64.8 ± 6.3 kg, fasting plasma glucose/insulin was 88.3 ± 5.6 mg/dL/3.6 ± 1.7 uU/mL, respectively, blood urea nitrogen (BUN)/Creatinine was 13.7 ± 2.8 mg/dL/0.97 ± 0.1 mg/dL, AST/ALT was 20.3 ± 8.6 IU/L/17.9 ± 13.4 IU/L, and the lipid profile (cholesterol/triglyceride/HDL/LDL) was 159.6 ± 26.6 mg/dL/103.3 ± 40.9 mg/dL/51.9 ± 8.0 mg/dL/96.4 ± 26.9 mg/dL, respectively. The mean value for body mass index was 20.8 ± 1.5 (Table 2). Personal medical history, physical examination, and baseline blood examination showed no associated diseases.

Fig. 1 shows the glucose profiles from CGMS and venous plasma glucose for each group, and the patterns and relationship between them. Values of postprandial venous plasma glucose levels of all groups were between 130 to 190 mg/dL. Plasma glucose 4 hours after eating was measured to be 60 to 90 mg/dL. The highest blood glucose measurement was 171 mg/dL, and the lowest blood glucose measurement was 71 mg/dL. The CGMS showed that peak postprandial glucose level was 120 to 140 mg/dL which was lower than that from plasma and the time to the peak glucose level was 45 to 75 minutes which was longer than 30 to 60minutes in plasma value. With the CGMS, the highest value was measured to be 131 mg/dL, and the lowest value was measured to be 71.6 mg/dL. The overall distribution pattern of intravenous glucose and CGMS values were similar in each group.

Looking at the CGMS and venous plasma glucose patterns from different types of diets (Fig. 2), the pattern of venous plasma glucose in all control diet and test meal reached approximately 100 to 190 mg/dL 30 to 45 minutes after consumption and then decreased in 60 minutes after meal, and normal fasting glucose level were seen 4 hours after meal. Additionally, the control diet resulted in the highest postprandial blood glucose level, and also the lowest postprandial venous plasma glucose level in all four groups, but it had no statistical significance.

Additionally, glucose value distribution measured with CGMS showed the similar pattern of postprandial increament in plasma glucose level, however, time to peak level was 45 to 60 minutes. Four hours after eating, the glucose level were similar to that from plasma again (Fig. 3). The highest and lowest glucose level in CGMS were also seen in the control diet and there was no significant difference in the value from CGMS and plasma in each group.

During the entire experimental period for all of the groups, when comparing the glucose level measured with CGMS and venous plasma glucose level, postprandial blood glucose patterns and even fasting plasma glucose level patterns decreased in a similar fashion. The time lag phenomenon in the peak postprandial glucose level between the CGMS value and plasma glucose were seen in gll group and all kinds of diet. Additionally, the difference between each of the CGMS and venous plasma glucose values for hyperglycemia period (45 to 60 minutes after eating), and hyperglycemia period (0 to 30 minuites after eating and 2 to 4 hours after eating) 34 ± 8.23 mg/dL, and 2.9 ± 4.94 mg/dL respectively, which confirmed that the accuracy in the hyperglycemic period was declining. The value from CGMS was lower than venous plasma glucose in all the time-section (16.3 ± 22.2 mg/dL). The correlation value between CGMS and venous plasma glucose was 0.73 (Fig. 4; regression analysis: slope = 1.08, intercept = 8.38 mg/dL). Additionally, correlation of these values, on the 1st day of clinical trials was 0.77, and on the 2nd day, it decreased to 0.65 (Figs. 5 and 6). These results were analyzed by error grid analysis (n = 1,568). Area A and area B are located at 95.4%, and CGMS's usefulness was confirmed (Fig. 7).