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Original Research
Green Tea Supplementation Affects Body Weight, Lipids,
and Lipid Peroxidation in Obese Subjects with
Metabolic Syndrome
Arpita Basu, PhD, RD, Karah Sanchez, MS, RD, Misti J. Leyva, MS, RD, Mingyuan Wu, MD, PhD, Nancy M. Betts, PhD, RD,
Christopher E. Aston, PhD, Timothy J. Lyons, MD, FRCP
Nutritional Sciences, Human Environmental Sciences, Oklahoma State University (A.B., K.S., N.M.B.), Stillwater, General Clinical
Research Center (M.J.L., C.E.A., T.J.L.), Harold Hamm Oklahoma Diabetes Center & Department of Medicine Endocrinology
(M.W., T.J.L.), University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
Objective: To compare the effects of supplementation of green tea beverage or green tea extracts with
controls on body weight, glucose and lipid profile, biomarkers of oxidative stress, and safety parameters in obese
subjects with metabolic syndrome.
Design: Randomized, controlled prospective trial.
Setting: General Clinical Research Center (GCRC) at University of Oklahoma Health Sciences Center
(OUHSC).
Subjects: Thirty-five subjects with obesity and metabolic syndrome were recruited in age- and gender-
matched trios and were randomly assigned to the control (4 cups water/d), green tea (4 cups/d), or green tea
extract (2 capsules and 4 cups water/d) group for 8 weeks. The tea and extract groups had similar dosing of
epiogallocatechin-3-gallate (EGCG), the active compound in green tea.
Methods: Anthropometrics, blood pressure, fasting glucose and lipids, nuclear magnetic resonance (NMR)-
based lipid particle size, safety parameters, biomarkers of oxidative stress (oxidized low-density lipoprotein
[LDL], myeloperoxidase [MPO], malondialdehyde and hydroxynonenals [MDA and HNE]), and free catechins
were analyzed at screen and at 4 and 8 weeks of the study.
Results: Pairwise comparisons showed green tea beverage and green tea extracts caused a significant
decrease in body weight and body mass index (BMI) versus controls at 8 weeks (22.5 60.7 kg, p,0.01, and
21.9 60.6, p,0.05, respectively). Green tea beverage showed a decreasing trend in LDL-cholesterol and
LDL/high-density lipoprotein (HDL) versus controls (p,0.1). Green tea beverage also significantly decreased
MDA and HNE (20.39 60.06 mM, p,0.0001) versus controls. Plasma free catechins were detectable in both
beverage and extract groups versus controls at screen and at 8 weeks, indicating compliance and bioavailability
of green tea catechins.
Conclusions: Green tea beverage consumption (4 cups/d) or extract supplementation (2 capsules/d) for
8 weeks significantly decreased body weight and BMI. Green tea beverage further lowered lipid peroxidation
versus age- and gender-matched controls, suggesting the role of green tea flavonoids in improving features of
metabolic syndrome in obese patients.
Address reprint requests to: Arpita Basu, PhD, RD, Assistant Professor, Nutritional Sciences, 301 Human Environmental Sciences, Oklahoma State University, Stillwater,
OK. E-mail: arpita.basu@okstate.edu
Abbreviations: ATP III 5Adult Treatment Panel III, BMI 5body mass index, BUN 5blood urea nitrogen, CV 5coefficient of variation, EC 5epicatechin, ECG 5
epicatechin gallate, EGC 5epigallocatechin, EGCG 5epigallocatechin-3-gallate, ELISA 5enzyme-linked immunosorbent assay, GCRC 5General Clinical Research
Center, Hb 5hemoglobin, HbA
1C
5glycated hemoglobin, HDL 5high-density lipoprotein, HNE 5hydroxynonenals, HOMA
IR
5homeostasis model assessment of
insulin resistance, HPLC 5high-performance liquid chromatography, IDL 5intermediate density lipoprotein, IRB 5institutional review board, LC 5liquid
chromatography, RD 5registered dietitian, LDL 5low-density lipoprotein, MCV 5mean corpuscular volume, MDA 5malondialdehyde, MeS 5metabolic syndrome,
MPO 5myeloperoxidase, NCEP 5National Cholesterol Education Program, NMR-LSP 5nuclear magnetic resonance-determined lipoprotein subclass profile, OSU 5
Oklahoma State University, OUHSC 5University of Oklahoma Health Science Center, OUMC 5University of Oklahoma Medical Center, ox-LDL 5oxidized LDL,
RBC 5red blood cell, SPSS 5Statistical Package for the Social Sciences, TSH 5thyroid-stimulating hormone, UV 5ultraviolet, VLDL 5very low density lipoprotein,
WBC 5white blood cell.
The authors have no conflicts of interest to report.
The abstract of this manuscript was presented in 2008 at the 49th Annual Meeting of the American College of Nutrition, at Arlington, VA, and received the Best Poster
Award.
Journal of the American College of Nutrition, Vol. 29, No. 1, 31–40 (2010)
Published by the American College of Nutrition
31
INTRODUCTION
Green tea (Camellia sinensis), traditionally used in Chinese
medicine, has gained scientific recognition in recent years for
its cardioprotective and weight loss effects [1–3]. The
antioxidant and antiobesity effects of green tea have been
associated with its catechin content: epiogallocatechin-3-
gallate (EGCG ,48%–55%), epigallocatechin (EGC ,9%–
12%), epicatechin gallate (ECG ,9%–12%), and epicatechin
(EC) (5%–7%), with EGCG being the most abundant and
pharmacologically active of the catechins [4]. Results of
epidemiologic studies in Asian countries have shown chronic
green tea consumption to be significantly associated with
reduced risks of cardiovascular disease [5–8]. Mechanistic
studies show that green tea catechins significantly decrease
low-density lipoprotein (LDL) oxidation [9], superoxide
production [10], vascular smooth muscle cell proliferation
[11], cholesterol absorption and serum cholesterol [12,13],
serum glucose [14], aortic lesion formation [15], and systolic
and diastolic blood pressure [16], thus causing an overall
attenuation in risk factors for atherosclerosis and hypertension.
Limited clinical trials have shown green tea intervention to
lower oxidative stress in smokers and healthy subjects [17–21]
and to improve insulin resistance and decrease glycated
hemoglobin (HbA
1C
) levels in patients with prediabetes or
diabetes [22,23]. However, most of these studies were
conducted among habitual green tea drinkers in Asian
countries [17,18,22,23] or had small sample size or short
study duration [18–20], or the interventions used green tea in
combination with a low-fat diet [21] or green tea formulations
not commercially available in the United States [20–23].
With an alarming rise in the prevalence of obesity and
metabolic syndrome (MeS) in the U.S. population [24,25], use
of alternative nutrition therapies, such as dietary supplements,
to promote weight loss [26] has been increasing. MeS, a
constellation of risk factors, including atherogenic dyslipide-
mia (low high-density lipoprotein [HDL], high triglyceride),
impaired fasting glucose, hypertension, and central adiposity,
also predisposes to higher risks of oxidative stress, type 2
diabetes, and atherosclerotic cardiovascular disease [27]. Diet
and exercise have been shown to improve oxidative stress,
insulin sensitivity, and atherosclerotic risk factors in subjects
with MeS [28]. Selected clinical trials in overweight and obese
subjects have shown green tea catechins to reduce body fat and
body weight or to maintain weight loss when catechin doses in
the range of 270–750 mg are used [29,30], although the effects
of green tea supplementation in the U.S. population with
metabolic syndrome have not been reported.
To examine the hypothesis that commercially available
green tea or extracts will reduce body weight, fasting glucose
and lipids, and oxidative stress in subjects with metabolic risk
factors, we conducted a randomized controlled study in 35 men
and women with MeS. The effects of green tea catechins on
anthropometrics, blood pressure, clinical variables, and
biomarkers of oxidative stress were investigated.
SUBJECTS AND METHODS
Subjects
Between January 2007 and December 2008, 41 subjects with
MeS were enrolled in the study at General Clinical Research
Center (GCRC) at University of Oklahoma Health Sciences
Center (OUHSC). Participants were recruited through flyers and
campus e-mail advertisements at OUHSC. Each potential recruit
underwent an initial telephone screening before the screening
visit. Potential recruits were excluded if they were younger than
21 years of age or had a pre-existing condition (e.g., diabetes,
cancer, heart disease), liver or renal disorders, or anemia.
Potential recruits also were excluded if they were consuming
.1 g/d of antioxidants/fish oil supplements, were current
smokers, were consuming alcohol on a regular basis (except
social drinking), or were pregnant or lactating. Written informed
consent was obtained from all potential recruits at the screening
visit. After the screening visit, potential recruits were enrolled in
the study if they met the definition of having MeS. As per the
National Cholesterol Education Program (NCEP) Adult Treat-
ment Panel III (ATP III) guidelines [31], MeS was defined as
having any 3 of the following 5 features: waist circumference
$102cminmenand$88 cm in women, triglycerides $150
mg/dL, HDL ,40 mg/dL in men or ,50 mg/dL in women, blood
pressure $130/85 mmHg, or fasting glucose $100 mg/dL.
Potential recruits were excluded if their hemoglobin (Hb), white
blood cells (WBCs), platelets, or liver, renal, or thyroid function
tests were outside of normal ranges. Subjects on stable
medications (except hypoglycemic and hypolipidemic agents)
were included in the study.
This randomized controlled trial was approved by the
Institutional Review Board (IRB) at OUHSC and at Oklahoma
State University (OSU).
Study Design
This was a randomized controlled trial with a single-blind
and permuted block randomization design. To account for the
effects of age and gender on the variables of interest,
participants were recruited into trios matched for age (65 years)
and gender. The age and gender for a trio were determined by
the first participant assigned to that trio. The next consecutive
participant who met the matching criteria of that trio was
assigned as the second participant of that trio, and so on. Each
trio had 1 participant in each of the 3 intervention groups: green
tea (4 cups/d), green tea extracts (2 capsules, 4 cups water/d), or
control (4 cups water/d). Although trios were filled consecu-
tively within the matching parameters, the intervention to which
Green Tea, Body Weight, and Lipid Peroxidation
32 VOL. 29, NO. 1
the first, second, and third participants in the trio were assigned
was predetermined by random permutation.
Participants in the control and green tea extract groups came
in for follow-up visits at 2, 4, 6, and 8 weeks. The green tea
beverage group made daily visits to the GCRC for a fresh supply
of tea. This was done to ensure compliance and consistency
because, in our opinion, instructing subjects to prepare the tea
themselves and drink 4 cups a day for 8 weeks would introduce
inconsistencies and lack of compliance. Subjects in the green tea
group consumed 2 cups of green tea in the morning at the GCRC
and were provided with another 2 cups in a container and were
asked to consume it at least 6–8 hours later in the day.
Participants were told not to reheat the tea that they consumed
later in the day, but to drink it straight from the container. The
Bionutrition Unit at GCRC prepared the green tea for the
subjects and monitored compliance.
Participants in the green tea extract or supplement group
were provided with containers to measure 4 cups of water to be
consumed on a daily basis and received a 2-week supply of
capsules during their follow-up visits, and they were instructed
to take 2 capsules a day, morning and evening, at least 6–
8 hours apart. Compliance was confirmed by pill count.
Participants in the control group were provided with containers
to measure 4 cups of water to be consumed on a daily basis. All
subjects were asked to refrain from any other source of green
tea, green tea supplements, and beverages containing green tea,
other than that provided by the study, and to maintain their
usual diet, physical activity, and lifestyle while enrolled in the
study. Subjects were asked to maintain 3-day food records at
baseline (screen) and at 4 and 8 weeks of the study. The
registered dietitian at GCRC provided forms and instructions
to subjects for use in maintaining dietary records. Upon
qualification and before randomization, all subjects were
trained by the Bionutrition staff at GCRC in recording portion
sizes by using food models and utensils. Participants turned in
food records at baseline and during their biweekly visits at 4
and 8 weeks. The Bionutrition staff was instructed not to
discuss diet or weight issues with participants to avoid
potential confounding factors that may arise as a result of
daily visits of the tea group versus weekly visits of the
supplement and control groups at the clinic. Subjects were
compensated during their follow-up visits.
Because we compared the effects of green tea beverage or
green tea extract capsules versus those of water, it was not
possible to blind participants to the interventions. However,
laboratory personnel and GCRC nurses were blinded to
participants’ intervention groups; recruitment and Bionutrition
staff members at the GCRC were not involved in physical
measurements or laboratory analyses. Participants were asked not
to discuss or mention their intervention with the GCRC nurses.
Fasting blood draws (45 mL) and blood pressure and
anthropometric measurements were performed at screen and at
4 and 8 weeks of the study. Fasting blood samples were tested
for insulin, glucose, and lipid profiles, as well as for safety
parameters, such as total protein, albumin, electrolytes,
hematology, and liver, renal, and thyroid function tests.
Fasting plasma samples were used for analyses of biomarkers
of oxidative stress and free catechins.
Green Tea and Extracts
Green tea bags were purchased from RC Bigelow
Incorporated (Fairfield, CT). Four decaffeinated green tea
bags were steeped in 4 cups of boiled water (8 oz/cup) for
10 minutes. No sugar or milk was added to the tea, but
artificial sweetener was used according to the preference of the
participants. Each cup of green tea provided approximately
110 mg of EGCG for a total of 440 mg EGCG per day. Four
cups provided a total of 928 mg catechins per day (Table 1).
The green tea extract supplements were purchased from
Solaray (Park City, UT). The capsules were manufactured
from the same lot numbers of raw materials. Each capsule
provided approximately 230 mg EGCG for a total of 460 mg
EGCG per day. Two capsules provided a total of 870 mg
catechins per day (Table 1). The capsules also included
vegetable cellulose, magnesium stearate, and silica as filler.
Catechin Analyses in Green Tea and Green
Tea Extracts
The catechin content, primarily EGCG, EGC, ECG, and
EC, and caffeine in green tea leaves (tea bags) and capsules
were analyzed through the procedure described previously by
Seeram et al. [32]. Briefly, 100 mg of green tea leaves or
extract powder was weighed and sonicated for 10 minutes in
methanol:water (1:1). The extracts were filtered (0.22 mm) and
analyzed on a Waters column (Symmetry C18, 100 mm 3
4.6 mm, 3.5 mm). The mobile phase consisted of acetonitrile
and 0.2% aqueous phosphoric acid under binary linear gradient
Table 1. Daily Dosage of Catechins from Green Tea and
Green Tea Extracts
1
Green Tea
2
(4 cups)
Green Tea Extracts
2
(2 capsules)
Total catechins (mg) 928.0 (100.0) 870.0 (100.0)
EGCG (mg) 440.0 (47.4) 460.0 (52.8)
EGC (mg) 220.0 (23.7) 240.0 (27.6)
ECG (mg) 180.0 (19.4) 120.0 (13.8)
EC (mg) 88.0 (9.5) 50.0 (5.8)
Caffeine (mg) 8.96 3.6
1
Total catechin concentration was defined as the sum of EGCG, EGC, ECG, and
EC values.
2
Percentage of total catechin in parentheses.
EC 5epicatechin, ECG 5epicatechin gallate, EGC 5epigallocatechin, EGCG
5epigallocatechin gallate.
Green Tea, Body Weight, and Lipid Peroxidation
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION 33
conditions. The wavelength was detected at 278 nm, and
catechins and caffeine were quantified with the use of
reference standards. All solvents were high-performance liquid
chromatography (HPLC) grade and were purchased from
Pharmco (Brookfield, CT). Caffeine and catechin standards
(EGCG, EGC, ECG, and EC) were purchased from Sigma
Aldrich Company (St. Louis, MO). The HPLC-ultraviolet
(UV) detection system consisted of a Waters 600 Controller
multisolvent delivery system pump, a Waters 717 plus Auto
sampler, a Waters 2487 Dual lAbsorbance Detector, and
Empower Pro software, Build 1154 (Waters, Milford, MA).
Plasma Catechin Analyses
Plasma free catechin analyses were performed by using a
modified version of the procedure of Masukawa et al. [33].
Briefly, 1 mL of heparinized plasma sample was mixed with
20 mL of 0.4 M phosphate buffer containing 20% ascorbic acid
and 0.1% disodium ethylenediaminetetraacetate (EDTA) and
was stored at 280uC for subsequent analyses within 3 months.
Before the assay was performed, 250 mL of thawed plasma was
mixed with 25 mL of 6 M perchloric acid and 125 mL
acetonitrile, was kept at 5uC for 30 minutes, and was
centrifuged at 16,000 3g for 10 minutes at 5uCina
Centrifuge 5415R (Eppendorf, Hamburg, Germany). The
supernatant was mixed with 100 mL of 0.75 M potassium
carbonate solution and centrifuged at 16,000 3gfor
10 minutes at 5uC to precipitate insoluble potassium
perchlorate; the resulting supernatant solution was subjected
to liquid chromatography (LC)-ultraviolet detection (UV) at
200 nm. The remaining HPLC conditions were similar to those
used for green tea and supplement analyses by Seeram et al.
[32]. All samples were run in duplicates, and plasma solutions
were spiked with green tea catechins (EGCG, EGC, ECG, EC)
for identification and quantification. The minimal detection
limit was 0.04, 0.02, 0.01, and 0.001 mmol/L in plasma for
EGC, EC, EGCG, and ECG, respectively.
Anthropometrics
Anthropometric measurements were obtained by trained
staff members at the GCRC. Height, weight, blood pressure,
waist circumference, and body fat percentage were measured
at screen and at 4- and 8-week visits. Participants removed
shoes and items in dress pockets and were weighed on a flat,
uncarpeted surface with the SECA 644 Multifunctional Hand
Rail Scale (SECA, Hamburg, Germany); weight was recorded
to the nearest 0.1 kg. Height was measured without shoes by
using the Accustat Genentech Stadiometer (San Francisco,
CA), and height was recorded to the nearest 0.1 cm. Systolic
and diastolic blood pressure was measured in mmHg with the
Spot Vital Signs Device (Welch Allyn, Skaneateles Falls, NY).
The Gulick II Tape Measure (Vital Signs, Gay Mills, WI) was
used to measure waist circumference in subjects at the superior
iliac crest. Body fat percentage was determined with the use of
Bodystat 1500 (Bodystat Ltd, Isle of Man, Great Britain) and
was based on bioelectrical impedance.
Dietary Analyses
Three-day averages of micronutrient and macronutrient
intakes were analyzed with Nutritionist Pro (version 3.2, 2007;
Axxya Systems, Stafford, TX). All data entry was performed
by registered dietitians (RDs) at GCRC who were trained and
certified in using the software. All dietary data entry was
verified by a second RD as a measure of quality control. If a
participant ate a food that was not in the database, a food with
very similar nutrient composition was chosen. Nutrient
information was also obtained from food labels or recipes
obtained from subjects or online sources or at grocery stores.
Clinical Analyses
Blood samples were collected immediately after each draw
at the GCRC and were transported to the University of
Oklahoma Medical Center (OUMC) Laboratory for analyses of
fasting glucose, insulin, lipid profile (total cholesterol,
triglycerides, LDLs, and HDLs), and other blood variables
(Hb, platelets, WBCs, red blood cells [RBCs], hematocrit,
mean corpuscular volume [MCV], liver enzymes, creatinine,
blood urea nitrogen [BUN], electrolytes, albumin, total protein,
and thyroid-stimulating hormone [TSH]). HbA
1C
was analyzed
at the GCRC with the use of a DCA 2000+(Bayer
Corporation, Elkhart, IN). Insulin resistance was evaluated
by homeostasis model assessment (HOMA
IR
)andwas
calculated as follows: Fasting insulin (mU/mL) 3Fasting
glucose (mmol/L)/22.5.
Nuclear magnetic resonance-determined lipoprotein sub-
class profile (NMR-LSP) was performed in first-thaw plasma
specimens with a 400-MHz proton NMR analyzer at
LipoScience Incorporated (Raleigh, NC), as described previ-
ously [34].
For oxidized LDL (ox-LDL), myeloperoxidase (MPO), and
malondialdehyde and hydroxynonenal (MDA and HNE)
assays, serum and EDTA-plasma samples were collected,
were separated by centrifugation (3000 rpm for 10 minutes at
4uC), and were stored at 280uC for subsequent analyses.
Biomarkers of Oxidative Stress
Plasma concentrations of MPO and ox-LDL were measured
in duplicate with enzyme-linked immunosorbent assay
(ELISA) kits (Mercodia, Uppsala, Sweden), according to the
manufacturers’ instructions. Lipid peroxidation was measured
in serum as malondialdehyde (MDA) and 4-hydroxynonenal
(HNE), with a colorimetric assay, according to the manufac-
turer’s protocol (LPO-586, Oxis Health Products, Incorporat-
Green Tea, Body Weight, and Lipid Peroxidation
34 VOL. 29, NO. 1
ed, Portland, OR). Average intra-assay coefficients of variation
(CVs) for MPO, ox-LDL, and MDA and HNE were 4.78%,
5.2%, and 3.56%, respectively.
Statistical Analyses
For all measures, descriptive statistics were calculated and
graphs drawn to look for outliers. Outliers due to data errors
were corrected where possible or were removed. Pairwise
differences (green tea versus control and green tea extracts
versus control) between the 3 groups at baseline were assessed
with the use of student t-tests. Changes in measurements over
the 8-week study period were assessed by calculating the
differences between preintervention and postintervention
measurements. Differences calculated for the green tea and
green tea extract groups were then conditioned on their
respective controls; the difference seen in the control
participant was subtracted from the difference seen in each
corresponding green tea and green tea extract participant
within the age- and gender-matched trio. These conditional
differences for the green tea and green tea extract groups were
assessed as being different from zero (no change) with the use
of student t-tests. All statistical tests were 2-tailed with
significance level set at 0.05. Significance levels were not
adjusted for multiple-hypothesis testing, rather the results were
reviewed for consistencies. The Statistical Package for the
Social Sciences (SPSS) for Windows (version 15.0; SPSS
Incorporated, Chicago, IL, 2006) was used for the statistical
calculations.
RESULTS
Catechin Content of Green Tea Beverage
and Extracts
The contents of EGCG, EGC, ECG, and EC are shown in
Table 1. The total EGCG content in 4 cups of green tea
beverage was 440 mg, and the 2 capsules of green tea extracts
provided 460 mg EGCG. Analyses were conducted at the
beginning, midpoint, and end of the 2-year study, and no
significant differences were noted in the catechin content of
green tea beverages and extracts. For the extracts, total
catechin and EGCG content per capsule were 108% and 92%
of label claims.
Baseline Characteristics
A total of 41 individuals were recruited for the study. Two
people withdrew for relocation and personal reasons, and 4
were withdrawn because of starting cholesterol (1) and
glucose-lowering (1) medications during the study, and for
smoking (2). Thus, a total of 35 subjects completed the study
with a mean age of 42.5 61.7 years and a mean body mass
index (BMI) of 36.1 61.3 kg/m
2
at screening visit. The 3 most
prominent features of MeS in our study sample were a large
waist circumference, elevated blood pressure or use of blood
pressure medications, and low HDL, as defined by NCEP ATP
III [31]. No significant differences were noted in baseline
characteristics except for total and LDL-cholesterol levels,
which were significantly higher in the control group than in
those taking green tea extracts (Table 2). Plasma gallated
catechins were nondetectable at baseline, except for EGC,
which was present at low concentrations in the control and
green tea groups.
Of 15 trios created throughout the 2-year study period, 11
were completed or had a control and tea or control and
supplement pair that could be used for comparisons. Trios
without a control participant had to be excluded from data
analyses. Thus, a total of 29 subjects were used in data
analyses; they formed 11 green tea–control and 7 green tea
extract–control pairs.
Anthropometrics and Blood Pressure
Compared with age- and gender-matched controls, average
body weight and BMI in the green tea beverage and extract
groups were significantly decreased over the 8-week period, as
shown in Table 3. Compared with age- and gender-matched
controls, no significant differences were noted in body fat,
waist circumference, or blood pressure for the green tea or
extract group.
Fasting Glucose, Lipids, Insulin Resistance,
HbA
1C
, NMR-LSP
Compared with age- and gender-matched controls, green
tea drinkers showed a decreasing trend in LDL-cholesterol and
LDL/HDL (p,0.1, Table 3). Also, data showed an increasing
trend in HDL among green tea drinkers versus controls (p5
0.08, Table 3). No significant differences were noted in fasting
glucose, insulin resistance, HbA
1C
, total cholesterol, or
triglycerides in the green tea group.
The green tea extract group showed no significant
differences in any of these parameters (Table 3). NMR-LSP
revealed an increasing trend in medium HDL particles in green
tea drinkers versus controls (p,0.1). However, green tea
extracts showed no significant differences in lipid particle
concentrations (Table 4).
Oxidative Stress and Plasma Catechins
Compared with age- and gender-matched controls, the
green tea group had a significant reduction in lipid peroxida-
tion measured as MDA and HNE over the 8-week study period
(Table 5); no significant effects were noted in ox-LDL and
MPO versus controls. Biomarkers of oxidative stress were not
affected by green tea extract supplementation.
Green Tea, Body Weight, and Lipid Peroxidation
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION 35
Plasma free catechin levels of EGC, EGCG, and ECG were
detectable and increased significantly in both green tea and
green tea extract groups compared with age- and gender-
matched controls, although the increase was greater in the tea
Table 2. Baseline Characteristics of Subjects (n 535) Enrolled in the Green Tea Study
1
Variable Control Green Tea Green Tea Extracts
N121310
Gender (female/male) 10/2 10/3 7/3
Age (years) 44.6 63.2 (25–63) 42.8 62.6 (28–59) 39.5 63.0 (27–52)
Weight (kg) 102.7 66.6 (76–154) 96.4 64.7 (67–123) 106.2 67.5 (69–138)
Body mass index (kg/m
2
) 36.4 62.8 (25–61) 34.6 61.5 (28–45) 38.0 62.3 (25–46)
Body fat (%) 44.0 63.4 (23–63) 42.0 62.8 (24–53) 42.0 62.8 (25–53)
Waist circumference (inches) 42.5 62.0 (35–55) 41.3 61.1 (35–47) 45.3 62.5 (37–58)
Systolic blood pressure (mmHg) 130 62.6 (113–141) 132 63.5 (119–161) 128 63.3 (114–150)
Diastolic blood pressure (mmHg) 80.0 62.1 (69–90) 83.0 62.2 (71–95) 82.0 61.7 (75–91)
Glucose (mg/dL) 90.0 64.1 (65–113) 89.0 63.2 (73–112) 85.0 62.8 (72–104)
Hemoglobin A
1C
(%) 5.6 60.1 (5.1–6.3) 5.5 60.1 (5.1–6.3) 5.5 60.1 (4.6–6.1)
Triglycerides (mg/dL) 129 621.0 (62–271) 175 625.0 (53–404) 161 626.6 (53–314)
Total cholesterol (mg/dL) 212 610.5 (158–264) 193.5 611 (143–283) 170 615 (108–249)*
LDL-cholesterol (mg/dL) 144 69.5 (91–206) 122 610.4 (84–196) 100 610.0(54–146)*
HDL-cholesterol (mg/dL) 42.0 62.0 (34–52) 40.0 62.1 (27–47) 38.0 65.0 (21–76)
LDL/HDL 3.5 60.3 (2.1–5.3) 3.1 60.3 (1.9–4.9) 3.0 60.3 (1.2–5.0)
HOMA
IR
3.0 60.4 (0.8–5.6) 3.0 60.4 (1.1–5.9) 3.2 60.6 (0.6–6.4)
Oxidized LDL (U/L) 104 610.6 (33–186) 104 67.2 (42–135) 91 69.1 (49–133)
Myeloperoxidase (mg/L) 70 64.7 (32–98) 63.3 62.8 (50–78) 74 64.2 (56–100)
Malondialdehyde and hydroxynonenal (mM) 1.14 60.02 (1.0–1.3) 1.2 60.04 (1.0–1.4) 1.2 60.04 (1.1–1.4)
Catechins (EGC, EGCG, ECG) (mmol/L) ND ND ND
1
Values represented as mean 6standard error (range).
* Significantly different from control (p,0.05).
ECG 5epicatechin gallate, EGC 5epigallocatechin, EGCG 5epigallocatechin gallate, HDL 5high-density lipoprotein, HOMA
IR
5homeostasis model assessment of
insulin resistance, LDL 5low-density lipoprotein, ND 5nondetectable.
Table 3. Pairwise Comparisons of Differences in Anthropo-
metrics, Blood Pressure, and Clinical Variables within Age-
and Gender-Matched Trios between 0 and 8 Weeks
1
Variable
Green Tea
versus Control
Green Tea Extracts
versus Control
Pairs (n) 11 7
Weight (kg) 22.5 60.7* 21.9 60.6
{
Body mass index (kg/m
2
)20.9 60.3* 20.7 60.2
{
Body fat (%) 20.3 60.9 0.2 61.3
Waist circumference
(inches) 0.4 60.9 21.6 61.0
Systolic blood pressure
(mmHg) 0.4 64.9 6.0 65.6
Diastolic blood pressure
(mmHg) 23.0 63.3 23.1 61.9
Glucose (mg/dL) 1.3 67.2 22.4 69.1
Hemoglobin A
1C
(%) 0.3 60.2 0.2 60.1
Triglycerides (mg/dL) 214.8 634.3 23.0 615.8
Total cholesterol (mg/dL) 20.7 65.2 211.4 69.9
LDL-cholesterol (mg/dL) 210.4 64.9
"
214.7 67.2
HDL-cholesterol (mg/dL) 3.0 61.7
l
21.1 62.6
LDL/HDL 20.4 60.2
j
20.3 60.2
HOMA
IR
0.2 60.6 0.7 60.7
1
Data represented as mean 6standard error.
* Significantly different from control (p#0.01).
{Significantly different from control (p,0.05).
l,",jp,0.1.
HDL 5high-density lipoprotein, hemoglobin A
1C
5glycated hemoglobin,
HOMA
IR
5homeostasis model assessment of insulin resistance, LDL 5low-
density lipoprotein, HOMA
IR
5homeostasis model assessment of insulin
resistance.
Table 4. Pairwise Comparisons of Differences in NMR-Based
Lipid Particle Concentration within Age- and Gender-Matched
Trios between 0 and 8 Weeks
1
Variable
Green Tea
versus Control
Green Tea Extracts
versus Control
Pairs (n) 11 7
Large VLDL and chylomicron
particles (nmol/L) 20.1 65.5 2.2 63.7
Medium VLDL particles
(nmol/L) 21.7 66.6 20.3 615.4
Small VLDL particles (nmol/L) 4.4 613.0 20.4 611.0
Large LDL particles (nmol/L) 165.4 6179.5 2177.7 6201.3
IDL particles (nmol/L) 55.1 644.7 214.0 647.0
Small LDL particles (nmol/L) 85.0 6266.4 281.6 6383.7
Large HDL particles (mmol/L) 1.1 61.3 20.4 62.5
Medium HDL particles (mmol/L) 3.4 61.7* V0.1 68.1
Small HDL particles (mmol/L) 21.6 62.4 6.4 64.6
VLDL mean particle size (nm) 0.1 64.7 1.2 63.7
LDL mean particle size (nm) 0.5 60.4 20.2 60.6
HDL mean particle size (nm) 0.4 60.3 20.2 60.3
1
Data represented as mean 6standard error.
* Significantly different from control (p,0.1).
HDL 5high-density lipoprotein, IDL 5intermediate-density lipoproteins, LDL
5low-density lipoprotein, VLDL 5very low–density lipoprotein.
Green Tea, Body Weight, and Lipid Peroxidation
36 VOL. 29, NO. 1
group than in those taking green tea extracts (Table 5). EC
levels were below the detection limits of our assay procedures.
No significant differences in dietary nutrient intakes were
noted at screen and at 8 weeks of the study (Table 6). All blood
reports were reviewed by the GCRC physician at screen and at
4 and 8 weeks, and no significant side effects were noted in
relation to the study. No effects were seen in safety parameters,
including hematology and liver, renal, and thyroid function
tests, in control, green tea, and extract groups.
DISCUSSION
To our knowledge, the study reported here is the first to
show that green tea beverage and extract supplementation for
8 weeks leads to a significant weight loss in obese subjects
with MeS compared with age- and gender-matched controls.
Our observations are consistent with previous findings in the
Asian population, in which green tea catechin supplementation
was shown to reduce body weight and body fat in overweight
and obese subjects [35–37]. However, it should be noted that in
comparison with these studies, subjects in our trial had higher
body weight and BMI, which may explain the fact that a
significant weight loss was observed over a shorter time
(8 weeks) versus previously reported findings in a 12-week
period [35–37]. This may suggest that the effects of green tea
may be more pronounced in subjects with clinically significant
obesity (BMI .35) with features of MeS than in healthy or
overweight adults. Studies reported by Hill et al. [38] and Maki
et al. [39] show that green tea catechin supplementation
together with exercise reduces abdominal fat and improves
features of MeS, such as fasting glucose and triglycerides, in
overweight or obese adults. The longer study duration
(12 weeks), the supervised exercise sessions, and the larger
sample size in these previous studies may explain the lack of
significant effects of green tea supplementation on fasting
glucose, insulin resistance, HbA
1c
, and triglycerides in our
study. However, in our study, green tea beverage supplemen-
tation showed a decreasing trend in LDL-cholesterol levels
while an increasing trend in HDL and medium HDL particle
concentrations was noted, suggesting an improvement in lipid
profile following green tea ingestion.
Because all subjects recruited in our study were from
OUHSC campus and were within close geographic proximity
of GCRC, subjects in the green tea beverage group were able
to come 5 days a week to drink their first 2 cups of tea at the
clinic, thus leading to high compliance among the green tea
drinkers. Also, the significant weight loss in the green tea
extract group further substantiates the fact that both beverage
and encapsulated forms of green tea catechins have weight loss
effects in obese subjects with MeS. Little is known about the
antiobesity effects of green tea, and the postulated hypothesis
states an inhibition of the catecholamine noradrenaline by
green tea extracts, thereby prolonging lipolysis leading to fat
oxidation and weight loss [40]. The lack of effect on blood
pressure seen with green tea intervention may be explained by
the fact that significant numbers of our sample (54% in the
green tea group and 60% in the green tea extract group) were
on stable blood pressure medications that could have masked
the reported antihypertensive effects of green tea [6,16].
A significant decrease in lipid peroxidation as MDA and
HNE among green tea drinkers in our study confirms the
antioxidant effects of green tea catechins, which have been
previously reported [19–21]. Thus, this decrease in oxidative
stress due to green tea beverage supplementation in obese
subjects with MeS may be significant in reducing the risks of
cardiovascular disease in this at-risk population. The lack of
effect of green tea extracts on biomarkers of oxidative stress
may be explained by the smaller sample size in this group
compared with the green tea beverage group and may indicate
the greater bioactivity of green tea beverage versus encapsu-
lated extracts. The green tea catechins were bioavailable in
both tea and extract groups, suggesting subject compliance. It
is interesting to note that our data showed that EGC was most
bioavailable, followed by EGCG, then ECG, confirming the
previous findings of lower plasma bioavailability of EGCG
compared with EGC [41,42]. Also, postprandial studies in
healthy subjects provided a single dose of green tea catechins
have shown peak concentrations within 2 hours and rapid
decline within 10–15 hours [42,43]. In contrast to these
postprandial studies, we provided equal dosing of green tea
catechins at 2 time points at least 6–8 hours apart, daily for
8 weeks, in subjects with MeS. Also, the total quantity of
catechins in our study was greater than in the doses provided
by Henning et al. [42] and in 2 of 3 doses given by Chow et al.
[43]. Thus, we were able to detect very low concentrations of
Table 5. Pairwise Comparisons of Differences in Markers of
Oxidative Stress and Plasma Catechins within Age- and
Gender-Matched Trios between 0 and 8 Weeks
1
Variable
Green Tea
versus Control
Green Tea Extracts
versus Control
Pairs (n) 11 7
Oxidized LDL (U/L) 215.6 610.86 10.0 614.1
Myeloperoxidase (mg/L) 224.8 616.7 27.4 619.2
Malondialdehyde and
hydroxynonenal (mM) 20.39 60.06* 20.11 60.05
Epigallocatechin (mmol/L) 0.09 60.008* 0.088 60.01*
Epigallocatechin gallate
(mmol/L) 0.036 60.004* 0.029 60.006
{
Epicatechin gallate (mmol/L) 0.003 60.0003* 0.002 60.0001*
1
Data represented as mean 6standard error.
* Significantly different from control (p,0.001).
{Significantly different from control (p,0.01).
LDL 5low-density lipoprotein.
Green Tea, Body Weight, and Lipid Peroxidation
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION 37
gallated catechins by using a 10–12 hour fasting blood sample,
indicating a possible delay in plasma clearance affected by
dose and frequency of dosing, as well as possible differences in
green tea catechin metabolism, among subjects with or without
MeS. This also suggests the need for a constant dietary supply
of flavonoid-rich foods and beverages to maintain adequate
plasma levels for cardiovascular health benefits.
The dietary data reveal low intakes of micronutrients,
specifically, vitamins C and E, in our subjects, which were
significantly below dietary reference intakes [44]. This is
mainly due to the participants’ inadequate intakes of specific
food groups containing vitamins C and E, such as fresh fruits,
vegetables, whole grains, and nuts, and frequent intakes of
convenience foods, which are poor sources of these nutrients.
Furthermore, adults in Oklahoma have a typically low fruit and
vegetable consumption, which may lead to low intakes of
micronutrients [45]. Although underestimation of portion sizes
reported by the participants may also be a contributing factor,
in general, most of the U.S. population does not meet the
recommendations for vitamins C and E (tocopherols) because
of poor food choices [46,47]. Thus, green tea supplementation
may be an effective source of antioxidants and antiobesity
Table 6. Dietary Nutrient Intakes at 0 and 8 Weeks
1
Variable
2
Control Green Tea Green Tea Extracts
N11117
Calories (kcal)
0 week 1900.31 6148.35 1911.34 6247.78 1986.82 6268.93
8 week 1842.76 6109.09 1935.78 6285.85 2088.63 6320.53
Carbohydrates (g)
0 week 222.21 632.65 218.75 634.68 229.40 645.82
8 week 213.98 622.65 223.08 646.13 220.67 642.84
Proteins (g)
0 week 71.73 615.13 82.43 614.51 82.51 66.40
8 week 69.82 616.21 79.06 68.95 84.50 615.5
Total fats (g)
0 week 81.45 613.65 81.44 616.83 82.0 66.63
8 week 72.44 68.13 84.73 613.56 85.1 610.6
Saturated fatty acids (g)
0 week 24.35 64.62 25.20 61.46 31.0 68.1
8 week 22.66 62.54 27.18 64.75 32.5 68.8
Monounsaturated fatty acids (g)
0 week 20.25 64.38 19.50 64.64 20.31 65.50
8 week 17.04 63.52 16.30 63.95 16.07 63.22
Polyunsaturated fatty acids (g)
0 week 12.05 62.68 11.04 63.44 10.82 63.67
8 week 10.49 62.14 10.05 64.38 9.67 62.62
Dietary fiber (g)
0 week 17.20 63.88 19.63 64.24 16.40 66.60
8 week 14.80 62.27 15.72 63.50 14.63 65.70
Vitamin A (IU)
0 week 2485.65 6617.85 2354.33 6237.86 2635.95 6249.74
8 week 2851.37 6583.73 2129.65 6437.93 2963.67 6274.69
Vitamin C (mg)
0 week 43.61 616.7 49.21 613.51 52.75 620.8
8 week 37.84 67.32 44.57 615.83 55.44 615.7
Vitamin E (mg)
0 week 2.47 60.93 3.20 60.84 3.25 60.93
8 week 2.20 60.58 4.36 60.93 2.78 60.74
1
Data represented as mean 6standard error.
2
p.0.05 for all variables.
Green Tea, Body Weight, and Lipid Peroxidation
38 VOL. 29, NO. 1
agents in subjects with MeS and inadequate micronutrient
consumption.
Our study has certain limitations. Our subjects were
recruited solely from the University of Oklahoma campus to
ensure compliance in the green tea beverage group and
therefore cannot be generalized to a larger population. Study
results could be influenced by any changes in physical activity
patterns that were not sufficiently monitored in the study,
except for the fact that participants during follow-up visits
were reminded not to change their usual diet and lifestyle.
Furthermore, differences in follow-up schedule between the
green tea beverage and extract groups may confound the lack
of significant effects in the latter.
In conclusion, this study shows beneficial effects of green
tea beverage and green tea extract supplementation on
cardiovascular risk factors in obese subjects with MeS.
Because our test agents were commercially available green
tea and green tea extracts, our study findings indicate the
benefits of a feasible and cost-effective cardioprotective
dietary intervention for the general public. Further investiga-
tion is clearly warranted to determine the mechanisms of
weight loss effects of green tea catechins in larger trials, to
define optimal dosing for cardiovascular benefit, and to
determine differences in beneficial effects among diverse
populations and subjects with varying degrees of metabolic
risk factors.
ACKNOWLEDGMENTS
The authors wish to thank Kavitha Penugonda for her
technical assistance in plasma catechin analyses, all OUHSC
employees for their participation in the study, and the
Bionutrition staff at GCRC for administration of intervention
and patient follow-up. This work was supported in part by the
University of Oklahoma Health Sciences Center General
Clinical Research Center grant M01-RR14467, National
Center for Research Resources, National Institutes of Health.
It was also supported by the College of Human Environmental
Sciences, Oklahoma State University.
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