Republic

AIMS
The aim of this study was to determine glycaemic index (GI) of 10 popular foodstuffs/mixed meals in healthy persons.


METHODS
Ten tested foodstuffs and glucose standard were consumed in three replicates in the course of a defined 9-day meal plan: puffed rice squares with chocolate, dark chocolate, white bread, honey and glucose for breakfast (at 7 a.m.) and dinner (at 8 p.m.); pasta with meat, fried fish with mashed potatoes, and buttered apricot dumplings for lunch (at 12 a.m.); wafers, puffed spelt squares with chocolate, and tomato soup for snack (at 4 p.m.). Each portion contained 50 g of carbohydrates and was consumed within 30 minutes. Glucose concentrations were measured by means of the Continous Glucose Monitoring System (CGMS, Medtronic Minimed, Northridge, CA, USA). The results were processed by Solutions Software (Medtronic Minimed, Northridge, CA, USA) and DegifXL4 software, Palacký University, Olomouc, CZ. Twenty healthy persons aged 21.9 +/- 1.39 y (mean +/- SE), BMI 23.6 +/- 0.63 kg/m(2) completed the study.


RESULTS
GI of tested foodstuffs ranged from 34.7 % (chocolate) to 105.3 % (puffed rice squares with chocolate). There were more than tenfold differences between minimal and maximal values of the GI for some foodstuffs. Significant interindividual differences were found between GIs of foodstuffs.


CONCLUSIONS
In twenty healthy persons the glycaemic indexes of ten popular foodstuffs were determined, to be added to the nutritional labels in order to facilitate the optimum meal planning.


INTRODUCTION
Glycaemic index (GI) is a measure of the hyperglycaemic power of food related to glucose.Since the pioneer papers of Otto 1 and Jenkins 2 it has become an important part of nutritional tabels 3 in many countries.However, the GI may be infl uenced by various factors, so that the determined values cannot be automatically transferred from one centre to another.
At The Faculty of Medicine of Palacký University, Olomouc attempts to determine the GI started in 2004, originally using the traditional methods [4][5][6] and recently also a new method based on CGMS and Software Solutions [7][8][9][10][11][12] and DegifXL 13,14 .Until now, the GI of only 6 foodstuff s had been determined.The aim of the present study was to determine the GI for other 10 popular foodstuff s/mixed meals.

MATERIALS AND METHODS
The study was performed in January and February 2007 as a part of the project DEGIF (IGA NR 7825-3).

Subjects
Twenty-fi ve healthy persons gave their informed consent according to the Declaration of Helsinki approved by the local Ethics Committee and entered the study.There were fi ve dropouts due to intercurrent illness.Twenty persons aged 21.9 ± 1.39 y (mean ± SE), BMI 23.6 ± 0.63 kg/m 2 , completed the study.

Tested foodstuff s
Ten diff erent foodstuff s/mixed meals with a known content of nutrients (Table 1) were tested.The tested meals were chosen from fi ve diff erent compartments of food: sweets, bakery, rice and spelt products and mixed meals.The choice of foods was also infl uenced by the amount of carbohydrates in one labeled marketed food package which should yield servings with 50 g ± 5 % of carbohydrates each.The portions were professionally prepared in the expected quality and quantity.
The foodstuff s were divided into 3 groups according to the time of consumption: Taking into consideration the content of nutrients and energetic values in each meal a defi ned meal plan was created (Tab.2).
Each foodstuff was consumed in three replicates, except for soup, which was consumed two times only.
Energetic values of tested foodstuff s for the whole day were 6000-9000 kJ (Tab.3).

Study design
1. CGMS sensor [15][16][17] , which was inserted subcutaneously into gluteal or lumbar region.Glycaemic index of selected foodstuff s in healthy persons 2. Each volunteer received personal glucometer Advance (Hypoguard, Woodbridge, UK) and 50 Microdraw strips for calibration of the CGMS.3. Volunteers were trained in handling the CGMS 18 .The average of two plasma glucose measurements on a glucometer Advance was taken to calibrate the CGMS every 12 hours.4. In the course of 9 test days, each volunteer entered the exact times of eating, exercise, glucose concentration measured on a glucometer and data on the function of the CGMS into the protocol.5. Every person received 32 servings of tested foods and the 9-day defi ned meal plan (Table 2).*p < 0.05 in comparison to glucose 6.Every volunteer was encouraged to drink 400 ml of water or unsweetend tea together with each meal.No drinks were to be taken one hour before the meal start and two hours afterwards.Each meal was to be consumed within 30 minutes 19 .7. Any diff erences in the daily routine were noted in the protocol.8. Having accomplished the meal plan, data were downloaded from the CGMS monitors into the PC to calculate the GIs using the Software Degif XL4 (Ref. 20), revised, manually corrected and completed according to protocols.The area under the curve has always been calculated for the period of time between 0 and 120 min.4.

Statistical analysis
MS Excel and the statistical program SPSS v. 14.0 (SPSS Inc., Chicago, IL, USA) were used to analyze the data: An ANOVA was applied to compare the GIs of tested foods; p<0.05 was considered statistically significant.

RESULTS
In comparison to glucose (GI = 100 %), four tested foodstuff s (dark chocolate, Ravioli pasta with cheese, puff ed spelt squares, tomato soup) were found to have lower GI (p < 0.05).No signifi cant diff erence in glucose was found for the 6 other foodstuff s (puff ed rice squares, white bread, lime-blossom honey, mashed potatoes with fried fi sh and butter, apricot dumplings with butter, wafers "Kolonáda").
Taking into consideration the traditional GI derived cathegories of foods, our results allow us to divide the tested foodstuff s/mix meals as follows: 1. group L: foods with low GI (GI ≤ 55 %): dark chocolate, Ravioli pasta with cheese, tomato soup 2. group M: foods with medium GI (GI = 56-69 %): puff ed spelt squares 3. group H: foods with high GI (GI ≥ 70 %): puff ed rice squares, white bread, honey, mashed potatoes with fi sh fi ngers and butter, buttered apricot dumplings, wafers "Kolonáda".
See Table 4 and Figure 1 for details.

DISCUSSION
The glycaemic index is an important component of nutritional labels.International tables containing the GIs of about 750 diff erent foodstuff s have been published 3 .The GIs of selected tested foodstuff s correspond to values of GI reported before.It is known that the GI of foods has a large inter-and intraindividual variability due to various factors.In this study we found more than tenfold diff erence between minimal and maximal values of the GI for some foodstuff s.Nevertheless, this fi nding corresponds with the fi ndings of other authors 21 .
We applied the CGMS to investigate the GIs.The values of GI obtained by this method were not statistically diff erent from values obtained by conventional method 22 .The CGMS sensor was safe for measuring the plasma glucose in the course of 9 days 23 .The function and accuracy of glucose sensors inserted for more than 3 days was also demonstrated 24 .In our study a total of 640 tests with 11 meals were performed and 491 (77 %) of these were complete and suitable for further evaluation 20 .
Conventional methods for GI determination involve usually ten healthy persons and tests are performed in the morning hours following overnight fast.In our study 20 healthy persons were tested to increase the precision of the outcomes.In order to increase the capacity of the investigational period not only breakfasts but also lunches, snacks and dinners were used.However, the real benefi ts of this study design remain to be established.Additionally, it is important to evaluate the glycaemic profi les of individuals in response to a given food e.g. the glycaemic response to a mixed meal 25 or to a complex food such as pizza.

CONCLUSIONS
In conclusion it may be said that the determined GIs of ten popular foods can facilitate nutritional labels to enable optimum meal planning 26,27 .A low GI was found for three foodstuff s (dark chocolate, Ravioli pasta with cheese, tomato soup), medium in puff ed spelt squares and high GI in six foodstuff s (puff ed rice squares, white bread, honey, mashed potatoes with fi sh fi ngers and butter, buttered apricot dumplings, wafers "Kolonáda").Further studies focused on other foodstuff s and mixed meals are necessary.

Table 1 .
Content of nutrients and energy in one portion of tested foodstuff

Table 2 .
Defi ned meal plan: a total of 32 servings of ten foodstuff s and standard (glucose)

Table 3 .
Total daily content of nutrients and energy in meals in the course of 9 test days.