Saddleback College



The effect of drinking green tea with starchy food on blood sugar spikes Somaye Gerannazar, Sara Arbabha, Negar Hesami Introduction Diabetes?has become increasingly prevalent in the past 20 years in the United States. During that time, there's been a growing epidemic of obesity and Type 2?diabetes. To prevent the development of these conditions scientific research has proposed several pharmacologic and non-pharmacologic means such as diet and exercise, during the past years. Tea is a part of dietary habits in many countries around the world. Although there are several types of tea (green, black, oolong and white), the moderate consumption of green tea has the most significant effects on human health. Bio-chemical analyses revealed that green tea contains significant amounts of vitamins and minerals, such as ascorbic acid (vitamin C), several B vitamins, such as riboflavin, niacin, folic acid, pantothenic acid, and magnesium, potassium, manganese and fluoride (Polychronopoulos et al., 2008). In particular, green tea may lower blood pressure and thus, reduce the risk of stroke and coronary heart disease. Some animal studies suggested that green tea may protect against the development of coronary heart disease by reducing blood glucose levels, and body weight (Polychronopoulos et al., 2008). In addition green tea has beneficial effects in prevention and treatment of many diseases, including type 2 diabetes. Based on this peer-reviewed article, and observations made in real life, it is likely that an ingredient in green tea including Epigallocatechin gallate (EGCG), which is the major catechin species found in green tea helps reduce blood sugar spikes (Higdon & Frei, 2003). The liver produces some glucose, but the most common sugar spikes occur from the food we eat. A recent study by Gao, Et al. (2013), suggested that green tea catechins may reduce the amount of glucose that passes through the intestine and into the bloodstream (Gao et al., 2013). Green tea extract contains polyphenols (e.g., catechin, epicatechin, epigallocatechin, and their gallates), teanin and caffeine (Josic et al., 2010).Tea catechins could play a role in controlling the dietary glucose uptake at the intestinal tract and possibly contribute to blood glucose homeostasis (Shimizu et al., 2000). This will benefit diabetics by preventing blood-sugar spikes when tea is taken with meals. The purpose of the study was to provide evidence of the improvement in glucose metabolism in humans upon green tea consumption. Furthermore this study evaluated that green tea consumption is associated with fasting blood glucose levels and investigated the effects of acute ingestion of green tea on blood glucose spikes 90 min after starchy food consumption. It was hypothesized that the intake of green tea will decrease the blood sugar spikes in young people without any disease. Methods A random sampling method was used to select 10 men and women aged 18-35, who resided in orange county, CA. All volunteer individuals were in good physical health, not taking any medications, and were non-smokers. For this study, which was conducted between 23 March and 7 April 2014, all participants were given written informed consent for participation, and the concept and procedure of the project was explained to them briefly. The design of the study was a crossover randomized control trial without blinding. Following a minimum 10-h overnight fast each volunteer completed 4 random days trial during a week. The experiment planned to start at 9 A.M each day; the blood sugar was tested via glucometer before the experiment, and every 15 minutes after food intake, for about 90 minutes (total of 7 measurements).During the first day participants were asked to drink 1 cup of water (250 mL); day two: 95 grams of Thomas'? plain bagels containing 52 g carbohydrate, with 2 tbsp of Kraft? Philadelphia cream cheese (2 g carbohydrate), with 1 cup of water (250 mL); day three: 1 cup (250 mL) of Mighty leaf? brewed green tea, and day four: 95 grams of Thomas'? plain bagel (52 g carbohydrate), 2 tbsp of Kraft? Philadelphia cream cheese (2 g carbohydrate), plus 1 cup (250 mL) of Mighty leaf? green tea. Blood glucose levels were recorded via glucometer, based on mg/dl units. Data collected during these four days need to be compared and analyzed. A one-way ANOVA will be conducted to compare blood glucose levels between the four different diets, to conclude whether there is a significant difference between the four groups. For further analysis between each paired group, a Post Hoc will be performed to compare individual pairs of groups. The purpose is to determine whether there is a significant difference between the green tea and carbohydrates diet, versus other three groups. Results Previous studies have shown that consumption of green tea might be effective in reducing blood glucose spikes, especially when ingested with food high in carbohydrate levels. An ingredient in green tea, including Epigallocatechin gallate (EGCG), which is the major catechin species, is presumed to be responsible for this effect (Higdon & Frei, 2003). In order to test this hypothesis 10 subjects were tested for blood glucose levels in the course of four days in 15 minute intervals for 90 minutes. The four experimental diet days will be abbreviated as W (water), W/B (water plus bagel), G (green tea) and G/B (green tea plus bagel). On each day the change in blood sugar spike was obtained from the fasting glucose and highest glucose level among the 7 measurements in each individual. Comparison of average blood glucose changes among four groups showed that the W/B diet showed the most variance in blood glucose spikes, and intake of G alone showed the least variance with a steady level of glucose among the 7 measurements (as shown in figure and table 1). In order to determine whether the changes among the four diet groups are significant or not, a single factor analysis of variance (ANOVA) test was performed. The calculated P value (3.99x10-10), which is less than 0.05 (p <0.05),indicates that there is a significant difference between the four different groups. Although there is a significant different among the four groups, the purpose of the proposed study was aimed at comparing spikes in glucose levels when carbohydrates are taken with green tea versus intake of carbohydrates with water. Therefore a post hoc Bonferroni correction was performed to compare individual pairs of group. Comparison of means in the six paired groups indicated that there is a significant different between pairs of W vs. W/B, W vs. G/W, B/W vs. G, B/W vs. B/G, and G vs. B/G. The only paired group without a significant difference was W vs. G (as shown in table 2). These results indicate that intake of green tea with starchy food is effective in lowering blood sugar spikes when compared with intake starchy food with water. Table 1. Frequency and average of diet categories?waterBagel+waterGreen TeaGreen tea+BagelMean4.242.23.425.1Standard Error1.0832051214.6875722220.6359594684.552044718Median338323Mode3#N/A2#N/AStandard Deviation3.42539535414.823404922.01108041714.39482932Sample Variance11.73333333219.73333334.044444444207.2111111Kurtosis-0.834770698-0.3517429842.322894923-1.237896725Skewness0.596314710.9229717341.3605938940.188840217Range1043740Minimum02716Maximum1070846Sum4242234251Count10101010Confidence Level (95.0%)2.45038021710.604025061.43864026210.29744054Figure1. Comparison of average blood glucose spikes in different diet groups. Results indicate that there is a significant difference between the four groups (p=3.99x10-10 < 0.05, Error bars are mean +/- SEM, single factor analysis of variance (ANOVA))Table2. Comparison and difference of blood sugar spikes in different paired groups??Comparison????Mean1 - Mean2????95% CI of difference????1:?W vs W/B??- 38.0??- 51.1 ?to? - 24.9?? ??2:?W vs G??+ 0.8??- 12.3 ?to? + 13.9?? ??3:?W vs G/W??- 20.9??- 34.0 ?to? - 7.8?? ??4:?B/W vs G??+ 38.8??+ 25.7 ?to? + 51.9?? ??5:?B/W vs B/G??+ 17.1??+ 4.0 ?to? + 30.2?? ??6:?G vs B/G??- 21.7??- 34.8 ?to? - 8.6?? Discussion Recent studies suggest that green tea catechins may reduce the amount of glucose that passes through the intestine and into the bloodstream. This will benefit diabetics by preventing blood-sugar spikes when tea is taken with starchy meals (Shimizu et al., 2000). The sugars and carbohydrates in our food are digested mainly in the duodenum, where they are converted to glucose and then absorbed into the blood. The agent that regulates the intake of blood sugar into the tissues is insulin, a chemical secreted from small Langerhans islands, which are on the pancreas. When starch is consumed, it requires the enzyme amylase to break it down into simple sugars that can be absorbed in the blood stream. In some studies, animal experiments showed that intake of green tea polyphenol increased insulin activity (Richarda & Dolansky, 2002). In fact, researchers have found that Green tea is loaded with catechin polyphenols, especially epigallocatechin gallate, which is commonly referred to as EGCG (also known as epigallocatechin gallete, one of the catechin polyphenols) influences the primary way that glucose is absorbed. EGCG may also help diabetics by mimicking the actions of insulin and inhibiting the liver’s production of glucose, thus lowering blood sugar (Higdon &Frei, 2003). The present study investigated the effects of green tea on glucose spikes after taking starchy food. The hypothesis was that drinking green tea with starchy food may help lower blood sugar spikes. Subjects were asked to fast 10 hours prior to the experiment day and individuals were tested in four different days with different dietary plans. Blood glucose levels were recorded based on mg/dl units, and data collected during these four days were compared and analyzed. As data from previous studies suggested that the consumption of green tea may be effective in reducing the blood glucose spikes when ingested with food high in carbohydrates, this study achieved the same results as well. The present initial results revealed statistically significant difference between the groups who consumed starchy food with Green tea, and other groups who only consumed starchy food with water (P= 3.99x10-10 < 0.05). Also comparison of average blood glucose changes among four groups showed that the group who consumed bagel and water showed the most variance in blood glucose spikes, and the group with intake of green tea alone showed the least variance with a steady level of glucose. Indeed the results indicate that green tea may be effective in reducing the blood sugar spikes in comparison with water, while starchy foods were consumed. Although further research needs to be performed on this topic, this information may be helpful for lowering the risk of type II diabetes in the future. Larger, population-based, randomized, controlled trials are required to further clarify the relationship between green tea consumption and the risk of type II diabetes.Acknowledgment The authors would like to thank all who participated and collaborated on this research. We’d also want thank Prof. Teh for lending his expertise.ReferencesCharles K. High sugar and low profile. In many people diabetes does damage without causing symptoms-so routine blood screening is important. Daily News New York [Internet]. [Cited 26 May 2010]; Final ed., sec. News; Daily checkup: 26. Available from: http: // .ezproxy.ivc.edu:2048/hottopics/InacademicGao J, Xu P, Wang Yu, Wang Yi, Hochstetter D. 2013. Combined Effects of Green Tea Extracts, Green Tea Polyphenols or Epigallocatechin Gallate with Acarbose on Inhibition against α-Amylase and α-Glycosidase in Vitro. Molecules, 18(9):11614-11623. Higdon JV, Frei B. 2003. Tea catechins and polyphenols: Health effects, metabolism and antioxidant functions. CRC Cr Rev Food Sci, 43(1): 89-143.Hsu C, Liao Y, Lin S, Tsai T, Huang C, Chou P. 2011. Does Supplementation with Green tea extract improve insuline resistance in Obese Type 2 Diabetics? A randomized, Double blind, and Placebo-controlled Clinical Trial.?Alternative Medicine Review, 16(2): 157-63. Josic J, Olsson A, Wickeberg J, Lindstedt S, Hlebowicz J. 2010. Does green tea affect postprandial glucose, insulin and satiety in healthy subject: a randomized controlled trial? Nutrition Jurnal, 9(1): 63-71. Available from: content/9/1/63.Polychronopoulos E, Zeimbekis A, Kastorini C, Papairakleous N, Vlachou I, BountzioukaV, B. Panagiotakos D. 2008. Effects of black and green tea consumption on blood glucose levels in non-obese elderly men and women from Mediterranean Islands (MEDIS epidemiological study). Original contribution, 47:10-16. Richarda A, Dolansky MM .2002. Tea enhances insulin activity.J Agric Food Chem 50:7182–7186.Shimizu M, Kobayash Y, Suzuki M, Satsu H, Miyamoto Y. 2000. Regulation of intestinal glucose transport by tea catechins. Biofactors, 13(1-4): 61-65.Venables MC, Hulston CJ, Cox HR, Jeukendrup AE. 2008. Green tea extracts ingestion, fat oxidation and glucose tolerance in healthy humans. Am J Clin Nutr, 87(3): 778-784. ................
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