Journal List > Nutr Res Pract > v.6(1) > 1051268

Yang, Kim, Yang, Kim, and Kwon: Dietary flavan-3-ols intake and metabolic syndrome risk in Korean adults

Abstract

Flavan-3-ols are a subclass of flavonoids found in a variety of foods including teas. The effects of flavan-3-ols on the risk of metabolic syndrome (MetS) have been investigated, generally focusing on tea catechins or individual flavan-3-ol rich foods, but there is little information on dietary flavan-3-ols intake and risk of MetS in population-based studies. In this cross-sectional study, we examined the association between dietary flavan-3-ols intake and the risk of MetS in Korean adults. Subjects comprised 1,827 men and 2,918 women aged 20-69 years whose data was included in the 2008 Korean National Health and Nutrition Examination Survey. This survey was conducted between January 2008 and December 2008. Total flavan-3-ols intakes were calculated from 24-hour dietary recalls using a flavonoids database. Thirty percent of the male subjects and 24% of the female subjects were reported as having MetS. In the female subjects, flavan3-ols intake was inversely associated with the risk of MetS after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.91, P for trend = 0.384). The main food source of flavan-3-ols was green tea followed by apples and grapes. Among MetS components, flavan3-ols intake was inversely associated with the risk of high blood pressure after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.90, P for trend = 0.005). No significant association between flavan-3-ols intake and risk of MetS was found in the male subjects. After stratified analysis by obesity (BMI ≥ 25 or BMI < 25), however, flavan3-ols intake was inversely related to the risk of hypertension in non-obese men. These results suggest that dietary flavan-3-ols intake may have beneficial effects on MetS risk by reducing the risk of hypertension. The effects of flavan-3-ols intake dependent on obesity need further investigation.

Introduction

Flavonoids are a class of plant secondary metabolites and are the most common group of polyphenolics in the human diet. According to their chemical structure, flavonoids are classified into several groups including flavonols, flavones, flavan-3-ols, flavanones, anthocyanidins, and isoflavonoids. Differences in the chemical structures of flavonoid subclasses alter their biological efficacy and bioavailability [1,2]. Flavan-3-ols are the collective term for the catechin group of compounds that have a 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. Catechin, epigallocatechin, epicatechin, epicatechin 3-gallate, epigallocatechin 3-gallate (EGCG), theaflavin, thearubigins, theaflavin-3,3-digallate, theaflavin-3-gallate, theaflavin-3'-gallate, gallocatechin, and catechin 3-gallate are included in flavan-3-ols. Food sources of flavan-3-ols include apples, hops, tea, beer, wine, fruit juice, and black tea [3].
Metabolic syndrome (MetS) is characterized by a clustering of metabolic abnormalities including abdominal obesity, hyperglycemia, hypertension, and dyslipidemia [4]. MetS is associated with developing type 2 diabetes, cardiovascular disease, and all-cause mortality [5,6]. Based on the 2005 Korean National Health and Nutrition Examination Survey (KNHANES), the prevalence of MetS in men and women was 32.9% and 31.8%, respectively. MetS is a complicated interaction between genetic, metabolic, and environmental factors, in which diet is a potent modifiable environmental factor. A number of foods, nutrients, and dietary patterns have been reported to be associated with MetS [7-9].
In recent years the effects of flavan-3-ols on the risk of MetS have been investigated. Green tea is rich in polyphenols, about 70% of which are catechins. Tea catechins have shown a relation with reduced serum cholesterol, serum triacylglycerol, and visceral fat area in animal studies [10-12]. Several epidemiological studies also have reported the beneficial effects of green tea consumption against cardiovascular disease risk [13-15]. Flavan-3-ols rich foods such as fruits, red wine, cocoa, and black tea also have been shown to reduce the risk of MetS or its components in human studies [16-19]. However, to our knowledge, no study has investigated the association of total flavan-3-ols intake from various kinds of flavan-3-ols [catechin, epigallocatechin, epicatechin, epicatechin 3-gallate, epigallocatechin 3-gallate (EGCG), theaflavin, thearubigins, theaflavin-3,3-digallate, theaflavin-3-gallate, theaflavin-3'-gallate, gallocatechin, and catechin 3-gallate] and the risk of MetS. Therefore, we examined the association between total flavan-3-ols intake and risk of MetS and its components (high blood pressure, hyperglycaemia, abdominal obesity, low HDL cholesterol, and hypertriglyceridaemia) in Korean adults.

Subjects and Methods

Study population

The Korean National Health and Nutrition Examination Survey (KNHANES) is a series of surveys designed to assess the health and nutritional status of the Korean population. The KNHANES began in 1998 and was conducted in 1998, 2001, and 2005. Since 2007, the KNHANES has been conducted annually. The KNHANES consists of a health interview, health examination (physical examination, clinical measurements, and tests), and a dietary interview. The subjects of the KNHANES were aged ≥ 1 year and were from stratified multistage samples of the South Korean population from multiple geographic areas, ages, and of both genders.
A total of 8,631 people participated in the 2008 KNHANES. We excluded subjects aged < 20 years or > 69 years (n = 3339), those who did not take the health examination (n = 310), those who reported implausible dietary intakes (< 500 kcal/d or > 4500 kcal) (n = 79), and those who did not have data on waist circumference, blood pressure, blood glucose, triglycerides, or high density lipoprotein (HDL)-cholesterol (n = 158). Finally, 4,745 subjects aged 20-69 years were included in the analysis. This study was approved by the Institutional Review Board (IRB) of Ewha Womans University. Written informed consent was obtained from all subjects.

General characteristics, anthropometrics, and biochemical variables

A structured questionnaire including information on demographics, education, smoking, alcohol intake, exercise, medical history, and female reproductive history was administered by trained interviewers. Height was measured within 0.1 cm and weight was measured with a metric weight scale to the nearest 0.01 kg in light clothing without shoes. Body mass index (BMI) was calculated as weight (kg)/height (m2). Waist circumference (WC) was measured according to the WHO guideline at the end of a normal expiration. Blood pressure measurements were taken three times, and the average of the second and third measurements for systolic blood pressure and diastolic blood pressure were used (Baumanometer, New York, USA). Blood samples were collected in the morning after at least ten hours of fasting and all biochemical markers were analyzed on the same day. Plasma total cholesterol, triglycerides, glucose, and high density lipoprotein (HDL) cholesterol were measured by an ADVIA1650 Automatic Analyzer (Siemens, New York, USA).

Diagnosis of metabolic syndrome

Metabolic syndrome was diagnosed if the subjects had three or more risk determinants according to the modified National Cholesterol Education Program Adult Treatment Panel III guidelines [20] using the standard waist circumference for Koreans [21]. The determinants were as follows: 1) a waist circumference ≥ 90 cm for men and ≥ 85 cm for women; 2) a plasma TG concentration of 150 mg/dL; 3) a plasma concentration of HDL-C < 40 mg/dL for men and < 50 mg/dL for women; 4) a systolic BP ≥ 130 mmHg and diastolic BP ≥ 85 mmHg; and 5) a fasting plasma glucose concentration ≥ 100 mg/dL.

Dietary assessment and flavonoid database

Trained dietitians interviewed each subject to collect dietary data through 24 hr dietary recalls. The daily flavan-3-ols intake from foods was estimated using a flavonoid database. Since a national nutrient database for flavonoids is not available in Korea, we constructed the flavonoid database for plant foods consumed by 8,631 subjects in the 2008 KNHANES from January 2008 to December 2008 using the United States Department of Agriculture (USDA) Flavonoid Content of Food Database [22], the Japan Functional Food Factor Database [23], and the Rural Development Administration Food Functional Composition Table [24]. For Korean foods with flavonoid analytic data, only data satisfied with a certain quality by the USDA nutrient data evaluation system were added to the database. Flavonoid contents for combination foods were calculated using standard recipes. If we could not find the same plant in other countries' database, we used data of a similar plant, based on species, genus, nutrients, shape, and color. The subjects of the 2008 KNHANES consumed 1,549 plant foods based on 24hr dietary recall data. The flavonoid database with 1,317 food items covered 85% of the plants foods consumed by the subjects of the 2008 KNHANES. When 1,549 foods were sorted by intake amounts from high to low, we defined the foods ranked ≤ the 95th percentile as 'commonly consumed food'. A total of 922 plant foods were classified into the commonly consumed food group, of which the flavonoids database covered 96%. Flavan-3-ols intake was the sum of catechin, epigallocatechin, epicatechin, epicatechin 3-gallate, epigallocatechin 3-gallate (EGCG), theaflavin, thearubigins, theaflavin-3,3-digallate, theaflavin-3-gallate, theaflavin-3'-gallate, gallocatechin, and catechin 3-gallate intakes.

Statistical analysis

Nutrient intakes were adjusted for total energy intake by the residual method. The subjects were categorized into quintiles by dietary flavan-3-ols intake. The Student's t-test and the Chi-square test were applied to determine differences in means and the distribution between the MetS group and control group. The general linear model (GLM) and Cochran Mantel Haenzel analysis were used to determine the linear trends across the flavan-3-ols intake groups. Non-conditional logistic regression analysis was applied to obtain the odds ratios (ORs) and corresponding 95% confidence intervals for MetS. Potential confounders were identified by examining the differences in means and distributions between the MetS group and control group. The variables that showed significantly different means or distributions between the MetS group and control group or showed significant linear trends across quintiles of flavan3-ols were considered as potential confounders and adjusted in the analyses. Three different models were applied to examine the associations of flavan-3-ols intake and MetS. Age and BMI were adjusted as confounders in the first model, and potential confounders except dietary factors were further adjusted in the second model. The final model additionally adjusted for dietary factors such as intakes of total energy, fat, fiber, and carbohydrate. All statistical analyses were performed using the SAS software (version 9.1 SAS Institute Inc., Cary, NC, USA), and P values < 0.05 were considered significant.

Results

The numbers of subjects for 20-29, 30-39, 40-49, 50-59, 60-69 years were 606, 1144, 1094, 966, and 935, respectively. Men made up 39% of the total subjects, and 30% of the male subjects and 24% of the female subjects were diagnosed as having MetS. Estimated means of daily total flavan3-ols intake for the men and women were 30.0 mg/d and 22.5 mg/d, respectively. The general characteristics of subjects are shown in Table 1. The means for age and BMI in the MetS group were higher than those in the control group for both male and female subjects. Education levels were higher in the control group than the MetS group for both the male and female subjects. In the male subjects, the mean intakes of energy, carbohydrate, fat, protein, and vegetables were higher in the control group than in the MetS group. There were no significant differences in flavan3-ols intake. In the female subjects, the proportions of current drinkers (defined as drinking alcohol more than once a month), and vitamin/mineral supplement use were higher in the control group than in the MetS group. In addition, mean intakes of energy, fat, protein, fruits, and flavan3-ols were higher in the control group than in the MetS group. The mean intakes of epigallocatechin, epicatechin, epicatechin 3-gallate, and EGCG were higher in the control group than in the MetS group.
To determine potential confounding factors, the distributions of selected characteristics were examined across quintiles of flavan-3-ol intake as shown in Table 2. In the male subjects, functional food use (%) and intakes of carbohydrate, fiber, and fruits increased across the quintiles of flavan3-ol intake. Conversely, regular exercisers (%) and intakes of energy and vegetables decreased across the quintiles of flavan3-ols intake. In the female subjects, height, current drinkers (%), multivitamin users (%) and intakes of carbohydrate, fiber, and fruits increased across the quintiles of flavan3-ol intake, but current smokers (%) and intakes of energy and vegetables decreased across the quintiles of flavan3-ols intake.
The top ten foods contributing flavan-3-ols in the diets of the male and female subjects are shown in Table 3. The main food source of flavan-3-ols was green tea followed by grapes, apples, and beer in the male subjects. In the females, green tea was the main food source of flavan-3-ols followed by apples, grapes, and pears.
The relationships between flavan-3-ols intake and the risk of MetS and MetS components are given in Table 4. No significant association between flavan-3-ols intake and the risk of MetS was found in male subjects. In the female subjects, flavan3-ols intake was inversely associated with the risk of MetS after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.91, P for trend = 0.384). When associations between flavan3-ols and each MetS component were determined, flavan3-ols intake was inversely associated with the risk of high blood pressure in female subjects after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.90, P for trend = 0.005).
To evaluate if the relationship between flavan3-ols intake and MetS risk was different according to the presence of obesity, a stratified analysis was applied based on BMI ≥ 25 or BMI < 25, as shown in Fig. 1 and 2. The proportions of obese subjects with BMI ≥ 25 were 37% and 28% of the male and female subjects, respectively. In the male subjects, flavan3-ols intake was inversely related to the risk of hypertension only in non-obese men. Among the female subjects, flavan3-ols intake was inversely associated with MetS risk after adjusting for potential confounders only in obese women. Among the components of MetS, flavan3-ols were inversely related to risks of hypertension and hyperglycaemia only in obese women. However, no significant relationships were found in non-obese women.

Discussion

In the present cross-sectional study, the relationship between flavan-3-ols intake and risk of MetS was investigated in male and female adult populations. Flavan-3-ols intake was not found to be related to the risk of MetS among the male subjects. Among the female subjects, flavan-3-ols intake was inversely associated with the risk of MetS. In particular, among the MetS components, flavan3-ols intake was inversely related to the risk of hypertension among the female subjects. After stratified analysis by obesity, flavan3-ols intake was inversely related to the risk of hypertension only in non-obese men. Among the female subjects, flavan3-ols intake was also inversely associated with risks of MetS, hypertension, and hyperglycaemia after adjusting for potential confounders only in obese women. The present findings suggest that flavan3-ols intake may have beneficial effects on the risk of MetS by reducing hypertension risk, and the effects of flavan3-ols may be different depending on the presence or absence of obesity.
Daily flavan-3-ols intake was estimated by 24-hr dietary recalls in the present study. The estimated means of daily flavan3-ols intake for men and women were 30.0 mg/d and 22.5 mg/d, respectively, which are lower than daily flavan3-ols intakes reported in other countries [25-27]. The main sources of flavan-3-ols were green tea, apples, grapes, pears, beer, and peaches in the present study. Intakes of flavan-3-ols in Australia, Denmark, and the Netherlands were 422 mg/d, 148 mg/d, and 145 mg/d, respectively. The main sources of flavan-3-ols were black tea, fruits, and red wine in the three countries [25]. Estimated daily flavan-3-ols intakes in the U.S. and Spain were 158 mg/d and 32 mg/d, respectively [26,27]. Low tea and red wine consumption in Korean adults may be attributed to their low intakes of flavan-3-ols.
Flavan-3-ols intake was inversely associated with the risk of MetS in female subjects, particularly with respect to hypertension. Green tea is the main dietary source of catechins gallates, and gallocatechins. Several epidemiological studies have reported the protective effects of green tea consumption against cardiovascular disease risk [13-15]. Chronic human intervention trials reported vasodilation effects of green tea and green tea extract [28,29]. Green tea consumption for two weeks showed a significant improvement in flow-mediated dilatation (FMD) assessed vascular reactivity among twenty smokers [28]. In a study by Tinahones et al., a group who consumed green tea extract showed higher vasodilation effects than a placebo group [29]. Several animal studies have also reported the beneficial vascular functions of green tea extract and EGCG [30-32]. Fruits, red wine, cocoa, and black tea also have been reported to reduce the risk of MetS or MetS components in many research settings including cohort studies, clinical trials, and cross-sectional studies [16-19].
The possible mechanisms underlying the impact of flavan-3-ols on vascular function are explained as follows. EGCG activates endothelial NO synthase (eNOS) in rat aortic rings [33]. It was also proposed that catechins may help regulate NADPH oxidase activity by reducing O2- production, which results in the protection of NO from peroxynitrite formation [34]. Increased NO bioavailability may explain the improvements in endothelial function (blood pressure). Since insulin sensitivity is, at least in part, dependent on nitric oxide bioavailability, flavan-3-ols may simultaneously improve insulin sensitivity as well as vascular function. Catechins and theaflavins prevented hyperglycaemia by enhancing insulin sensitivity and by decreasing pancreatic β-cell damage in an animal study [35]. Another plausible mechanism is that EGCG increases prostacyclin (PGI2) production which is known as a potent vasodilator. EGCG dose-dependently increased PGI2 production in bovine endothelial cells [36]. Flavan-3-ols from fruits improved indices of MetS in animal models [37], but more studies examining flavan-3-ols from fruits are needed.
The effects of flavan-3-ols on MetS were different by obesity. In the male subjects, flavan-3-ols intake was inversely related to the risk of hypertension only in non-obese men. Among the female subjects, the beneficial effects of flavan-3-ols on MetS were shown in only obese women. These results suggest that the effects of flavan-3-ols on MetS may be different depending on body fat composition. We could not find a previous study that compared the effects of flavan-3-ols by gender or weight status. Further studies on the effects of flavan-3-ols in normal, overweight, and obese subjects by gender are necessary.
The limitations of this study need to be considered when interpreting the findings. Since it was a cross-sectional study, we cannot conclude a causality of flavonoid intake and MetS. Due to large intra-individual variability in food and nutrient intakes of most people, a one-day 24 hr dietary recall is not sufficient to estimate usual daily flavan-3-ols intake. Since a national nutrient database on flavonoids is not available in Korea, we constructed a flavonoid database using the USDA Flavonoid Database [22], the Japan Functional Food Factor Database [23], and the Rural Development Administration Food Functional Composition Table [24], which covered 85% of plants foods and 96% of the most commonly consumed foods in the 2008 KNHANES. Missing flavan-3-ols values in the database would have decreased the estimation of flavan-3-ols intake. Moreover, there is large variability in the flavonoid content of foods depending on cultivating season and methods, geographical origin, and processing; thus, the flavonoid contents of foods commonly consumed by Koreans need to be analyzed in further studies.
Despite these limitations, the results of this study suggest that flavan-3-ols intake may have beneficial effects on MetS, particularly by reducing the risk of hypertension. These beneficial effects may be different between non-obese and obese individuals. Further investigations including clinical trials and cohort studies are required to confirm these findings.

Figures and Tables

Fig. 1
Adjusted ORs and 95% CIs of MetS and MetS components by quintiles of flavan-3-ols in males according to obesity after adjusting for age, BMI, education (elementary, middle, high, college), current smoking (yes/past/no), regular exercise (yes/no), functional food use (yes/no), and intakes of total energy, fat, and fiber.
nrp-6-68-g001
Fig. 2
Adjusted ORs and 95% CIs of MetS and MetS components by quintiles of flavan-3-ols in females according to obesity after adjusting for age, BMI, education (elementary, middle, high, college), current drinking (more than once a month/none), vitamin/mineral supplement use (yes/no), functional food use (yes/no), and intakes of total energy, fat, fiber, and carbohydrate.
nrp-6-68-g002
Table 1
Characteristics of subjects with and without metabolic syndrome (MetS)
nrp-6-68-i001

1)BMI, body mass index; BP, blood pressure; HDL, high-density lipoprotein; HOMA-IR, homeostasis model assessment estimate of insulin resistance

2)Mean ± SD

Table 2
Selected characteristics of subjects according to quintiles of flavan-3-ols intake
nrp-6-68-i002

BMI, body mass index; Q, quintile

Table 3
Contribution of primary individual foods to favan-3-ols intake
nrp-6-68-i003

1)% of total flavan-3-ols intake

2)Acc stands for Accumulation

Table 4
Adjusted odd radios (ORs), and 95% confidence intervals (CIs) of MetS and MetS components by quintiles of flavan-3-ols intake
nrp-6-68-i004

Q, quintile; HDL, high-density lipoprotein

1)Model 1; adjusted for age, body mass index, Model 2; adjusted for all variables in model 1 plus education (elementary, middle, high, college), current smoking (yes/past/no), regular exercise (yes/no), functional food use (yes/no), Model 3; adjusted for all variables in model 2 plus intakes of total energy, fat, and fiber.

2)Model 1; adjusted for age, body mass index, Model 2; adjusted for all variables in model 1 plus education (elementary, middle, high, college), current drinking (more than once a month/none), vitamin/mineral supplement use (yes/no), functional food use (yes/no), Model 3; adjusted for all variables in model 2 plus intakes of total energy, fat, fiber, and carbohydrate

Notes

The paper was supported by RP-Grant 2010 of Ewha Womans University.

References

1. Williamson G, Manach C. Bioavailability and bioefficacy of polyphenols in humans. II. Review of 93 intervention studies. Am J Clin Nutr. 2005. 81:243S–255S.
crossref
2. Manach C, Williamson G, Morand C, Scalbert A, Rémésy C. Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies. Am J Clin Nutr. 2005. 81:230S–242S.
crossref
3. Yao LH, Jiang YM, Shi J, Tomás-Barberán FA, Datta N, Singanusong R, Chen SS. Flavonoids in food and their health benefits. Plant Foods Hum Nutr. 2004. 59:113–122.
crossref
4. Bonora E, Kiechl S, Willeit J, Oberhollenzer F, Egger G, Bonadonna RC, Muggeo M. Bruneck Study. Metabolic syndrome: epidemiology and more extensive phenotypic description. Cross-sectional data from the Bruneck Study. Int J Obes Relat Metab Disord. 2003. 27:1283–1289.
crossref
5. Wilson PW, D'Agostino RB, Parise H, Sullivan L, Meigs JB. Metabolic syndrome as a precursor of cardiovascular disease and type 2 diabetes mellitus. Circulation. 2005. 112:3066–3072.
crossref
6. Ford ES. Risks for all-cause mortality, cardiovascular disease, and diabetes associated with the metabolic syndrome: a summary of the evidence. Diabetes Care. 2005. 28:1769–1778.
crossref
7. Sahyoun NR, Jacques PF, Zhang XL, Juan W, McKeown NM. Whole-grain intake is inversely associated with the metabolic syndrome and mortality in older adults. Am J Clin Nutr. 2006. 83:124–131.
crossref
8. Liu S, Song Y, Ford ES, Manson JE, Buring JE, Ridker PM. Dietary calcium, vitamin D, and the prevalence of metabolic syndrome in middle-aged and older U.S. women. Diabetes Care. 2005. 28:2926–2932.
crossref
9. Kim JA, Kim SM, Lee JS, Oh HJ, Han JH, Song Y, Joung H, Park HS. Dietary patterns and the metabolic syndrome in Korean adolescents: 2001 Korean National Health and Nutrition Survey. Diabetes Care. 2007. 30:1904–1905.
10. Kobayashi M, Unno T, Suzuki Y, Nozawa A, Sagesaka Y, Kakuda T, Ikeda I. Heat-epimerized tea catechins have the same cholesterol-lowering activity as green tea catechins in cholesterol-fed rats. Biosci Biotechnol Biochem. 2005. 69:2455–2458.
crossref
11. Ikeda I, Tsuda K, Suzuki Y, Kobayashi M, Unno T, Tomoyori H, Goto H, Kawata Y, Imaizumi K, Nozawa A, Kakuda T. Tea catechins with a galloyl moiety suppress postprandial hypertriacylglycerolemia by delaying lymphatic transport of dietary fat in rats. J Nutr. 2005. 135:155–159.
crossref
12. Ikeda I, Hamamoto R, Uzu K, Imaizumi K, Nagao K, Yanagita T, Suzuki Y, Kobayashi M, Kakuda T. Dietary gallate esters of tea catechins reduce deposition of visceral fat, hepatic triacylglycerol, and activities of hepatic enzymes related to fatty acid synthesis in rats. Biosci Biotechnol Biochem. 2005. 69:1049–1053.
crossref
13. Imai K, Nakachi K. Cross sectional study of effects of drinking green tea on cardiovascular and liver diseases. BMJ. 1995. 310:693–696.
crossref
14. Sano J, Inami S, Seimiya K, Ohba T, Sakai S, Takano T, Mizuno K. Effects of green tea intake on the development of coronary artery disease. Circ J. 2004. 68:665–670.
crossref
15. Kuriyama S, Shimazu T, Ohmori K, Kikuchi N, Nakaya N, Nishino Y, Tsubono Y, Tsuji I. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006. 296:1255–1265.
crossref
16. Høstmark AT. The Oslo Health Study: a Dietary Index estimating high intake of soft drinks and low intake of fruits and vegetables was positively associated with components of the metabolic syndrome. Appl Physiol Nutr Metab. 2010. 35:816–825.
crossref
17. Miura K, Greenland P, Stamler J, Liu K, Daviglus ML, Nakagawa H. Relation of vegetable, fruit, and meat intake to 7-year blood pressure change in middle-aged men: the Chicago Western Electric Study. Am J Epidemiol. 2004. 159:572–580.
crossref
18. Andrade AC, Cesena FH, Consolim-Colombo FM, Coimbra SR, Benjó AM, Krieger EM, Luz PL. Short-term red wine consumption promotes differential effects on plasma levels of high-density lipoprotein cholesterol, sympathetic activity, and endothelial function in hypercholesterolemic, hypertensive, and healthy subjects. Clinics (Sao Paulo). 2009. 64:435–442.
crossref
19. Grassi D, Mulder TP, Draijer R, Desideri G, Molhuizen HO, Ferri C. Black tea consumption dose-dependently improves flow-mediated dilation in healthy males. J Hypertens. 2009. 27:774–781.
crossref
20. Grundy SM, Brewer HB Jr, Cleeman JI, Smith SC Jr, Lenfant C. American Heart Association. National Heart, Lung, and Blood Institute. Definition of metabolic syndrome: Report of the National Heart, Lung, and Blood Institute/American Heart Association conference on scientific issues related to definition. Circulation. 2004. 109:433–438.
21. Lee SY, Park HS, Kim DJ, Han JH, Kim SM, Cho GJ, Kim DY, Kwon HS, Kim SR, Lee CB, Oh SJ, Park CY, Yoo HJ. Appropriate waist circumference cutoff points for central obesity in Korean adults. Diabetes Res Clin Pract. 2007. 75:72–80.
crossref
22. USDA Database for the Flavonoid Content of Selected Foods. Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Agricultural Research Service [Internet]. cited 2007 January 31. Available from: http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/Flav/Flav02-1.pdf.
23. Functional Food Factor. National Institute of Health and Nutrition in Japan [Internet]. cited 2008 January 20. Available from: http://www.nih.go.jp/eiken/english/index.html.
24. National Academy of Agricultural Science. Tables of Food Functional Composition. 2009. Suwon: National Academy of Agricultural Science.
25. Johannot L, Somerset SM. Age-related variations in flavonoid intake and sources in the Australian population. Public Health Nutr. 2006. 9:1045–1054.
crossref
26. Zamora-Ros R, Andres-Lacueva C, Lamuela-Raventós RM, Berenguer T, Jakszyn P, Barricarte A, Ardanaz E, Amiano P, Dorronsoro M, Larrañaga N, Martínez C, Sánchez MJ, Navarro C, Chirlaque MD, Tormo MJ, Quirós JR, González CA. Estimation of dietary sources and flavonoid intake in a Spanish adult population (EPIC-Spain). J Am Diet Assoc. 2010. 110:390–398.
crossref
27. Chun OK, Chung SJ, Song WO. Estimated dietary flavonoid intake and major food sources of U.S. adults. J Nutr. 2007. 137:1244–1252.
crossref
28. Kim W, Jeong MH, Cho SH, Yun JH, Chae HJ, Ahn YK, Lee MC, Cheng X, Kondo T, Murohara T, Kang JC. Effect of green tea consumption on endothelial function and circulating endothelial progenitor cells in chronic smokers. Circ J. 2006. 70:1052–1057.
crossref
29. Tinahones FJ, Rubio MA, Garrido-Sánchez L, Ruiz C, Gordillo E, Cabrerizo L, Cardona F. Green tea reduces LDL oxidability and improves vascular function. J Am Coll Nutr. 2008. 27:209–213.
crossref
30. Antonello M, Montemurro D, Bolognesi M, Di Pascoli M, Piva A, Grego F, Sticchi D, Giuliani L, Garbisa S, Rossi GP. Prevention of hypertension, cardiovascular damage and endothelial dysfunction with green tea extracts. Am J Hypertens. 2007. 20:1321–1328.
crossref
31. Potenza MA, Marasciulo FL, Tarquinio M, Tiravanti E, Colantuono G, Federici A, Kim JA, Quon MJ, Montagnani M. EGCG, a green tea polyphenol, improves endothelial function and insulin sensitivity, reduces blood pressure, and protects against myocardial I/R injury in SHR. Am J Physiol Endocrinol Metab. 2007. 292:E1378–E1387.
crossref
32. Miura Y, Chiba T, Tomita I, Koizumi H, Miura S, Umegaki K, Hara Y, Ikeda M, Tomita T. Tea catechins prevent the development of atherosclerosis in apoprotein E-deficient mice. J Nutr. 2001. 131:27–32.
crossref
33. Lorenz M, Wessler S, Follmann E, Michaelis W, Düsterhöft T, Baumann G, Stangl K, Stangl V. A constituent of green tea, epigallocatechin-3-gallate, activates endothelial nitric oxide synthase by a phosphatidylinositol-3-OH-kinase-, cAMP-dependent protein kinase-, and Akt-dependent pathway and leads to endothelial-dependent vasorelaxation. J Biol Chem. 2004. 279:6190–6195.
crossref
34. Schewe T, Steffen Y, Sies H. How do dietary flavanols improve vascular function? A position paper. Arch Biochem Biophys. 2008. 476:102–106.
crossref
35. Anderson RA, Polansky MM. Tea enhances insulin activity. J Agric Food Chem. 2002. 50:7182–7186.
crossref
36. Mizugaki M, Ishizawa F, Yamazaki T, Hishinuma T. Epigallocatechin gallate increase the prostacyclin production of bovine aortic endothelial cells. Prostaglandins Other Lipid Mediat. 2000. 62:157–164.
crossref
37. Kalgaonkar S, Nishioka H, Gross HB, Fujii H, Keen CL, Hackman RM. Bioactivity of a flavanol-rich lychee fruit extract in adipocytes and its effects on oxidant defense and indices of metabolic syndrome in animal models. Phytother Res. 2010. 24:1223–1228.
crossref
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