The Green Tea Reference Library
Green tea on obesity
(1) Daily consumption of green tea containing 690 mg
catechins for 12 wk reduced body fat in humans significantly.
BACKGROUND: Catechins, the major component of green tea
extract, have various physiologic effects. There are few studies, however,
on the effects of catechins on body fat reduction in humans. It has been
reported that the body mass index (BMI) correlates with the amount of
malondialdehyde and thiobarbituric acid-reactive substances in the blood.
OBJECTIVE: We investigated the effect of catechins on body fat reduction
and the relation between oxidized LDL and body fat variables. DESIGN:
After a 2-wk diet run-in period, healthy Japanese men were divided into 2
groups with similar BMI and waist circumference distributions. A 12-wk
double-blind study was performed in which the subjects ingested 1 bottle
oolong tea/d containing 690 mg catechins (green tea extract group; n = 17)
or 1 bottle oolong tea/d containing 22 mg catechins (control group; n =
18). RESULTS: Body weight, BMI, waist circumference, body fat mass, and
subcutaneous fat area were significantly lower in the green tea extract
group than in the control group. Changes in the concentrations of
malondialdehyde-modified LDL were positively associated with changes in
body fat mass and total fat area in the green tea extract group.
(2) Green tea modulates the glucose uptake and
suppresses the expression of adipogenesis-related transcription factors,
as the possible mechanisms of its anti-obesity actions.
To investigate mechanisms of the anti-obesity actions of green tea in vivo, rats were given green tea instead of drinking water for 3 weeks. It was confirmed that green tea reduced adipose tissue weight without any change in body weight, other tissue weights, and food and water intakes. Green tea also significantly reduced the plasma levels of cholesterols and free fatty acids. Certain catechins existed in the plasma at 0.24 microM under our experimental conditions, though most of them existed as conjugated forms. For mechanisms of the anti-obesity actions, green tea significantly reduced glucose uptake accompanied by a decrease in translocation of glucose transporter 4 (GLUT4) in adipose tissue, while it significantly stimulated the glucose uptake with GLUT4 translocation in skeletal muscle. Moreover, green tea suppressed the expression of peroxisome proliferator-activated receptor gamma and the activation of sterol regulatory element binding protein-1 in adipose tissue. In conclusion, green tea modulates the glucose uptake system in adipose tissue and skeletal muscle and suppresses the expression and/or activation of adipogenesis-related transcription factors, as the possible mechanisms of its anti-obesity actions.
(3) Green tea caused glycerol release from the fat
cells, a mechanism for obesity control.
The influence of catechins in green tea on lipolysis in fully differentiated 3T3-L1 cells was studied and glycerol release into the buffer, cytosol and residual triglyceride were measured.The addition of (-)-epigallocatechin-3-gallate (EGCG) stimulated glycerol release into the cytosol significantly after incubation for 4 h, but had no effect on that into the buffer. However, (+)-catechins did not produce a significant increase in lipolysis. These data suggested that EGCG has strong lipolytic activity.
(4) Raederstorff DG, Schlachter MF, Elste V, Weber P. Effect of EGCG on lipid absorption and plasma lipid levels in rats. J Nutr Biochem. 2003 Jun;14(6):326-32.
Catechins, compounds derived from green tea, have been shown to reduce plasma cholesterol levels and the rate of cholesterol absorption. We investigated the dose response and the mechanism of action of epigallocatechin gallate (EGCG) on these parameters in rats. Wistar rats were fed a diet high in cholesterol and fat containing either none, 0.25% (0.2 g/day/kg BW), 0.5% (0.4 g/day/kg/BW) or 1.0% (0.7 g/day/kg BW) of EGCG. After 4 weeks of treatment, total cholesterol and low density lipoprotein plasma levels were significantly reduced in the group fed 1% EGCG when compared to the no treatment group. Plasma triglycerides and high-density lipoprotein levels did not change significantly. Following a single oral application of a liquid test-meal, intestinal cholesterol absorption in Wistar rats was 79.3% in the control group. In the group treated with 0.1 g/kg BW EGCG intestinal cholesterol absorption decreased to 73.7% and in the group treated with 0.5 g/kg BW of EGCG intestinal cholesterol absorption fell significantly to 62.7% (P = 0.005). Total fat absorption was very efficient in the control group (99.5% of the applied dose) and decreased significantly but moderately in the group treated with the highest doses of EGCG (0.75, 1 g/kg BW). In an in-vitro biliary micelle model, the addition of 55 microM to 1300 microM EGCG not only decreased cholesterol solubility dose-dependently in these micelles but also altered the size of the mixed lecithin/taurocholate/cholesterol micelles as demonstrated by light scattering. This study provides evidence suggesting that the cholesterol-lowering effect of green tea is mainly elicited by EGCG, one of the most abundant catechins contained in green tea. It is suggested that one of the underlying mechanisms by which EGCG affects lipid metabolism is by interfering with the micellar solubilization of cholesterol in the digestive tract, which then in turn decreased cholesterol absorption.
(5) Hasegawa N, Yamda N, Mori M. Powdered green tea has antilipogenic effect on Zucker rats fed a high-fat diet. Phytother Res. 2003 May;17(5):477-80.
The effect of powdered green tea on the lipid metabolism was studied in male Zucker rats fed a 50% sucrose diet containing 15% butter. The oral treatment of 130 mg powdered green tea per day depressed body weight increase and various adipose tissue weights but food intake was unaffected. The treatment also slightly increased the plasma triglycerides. These effects were likely mediated by the inhibition of lipogenesis in the adipose tissues. The experimental group had a higher concentration of liver total lipid, triglycerides and plasma protein, and lower liver weights than the controls. This may be due to lipid deposition in the liver because of the reduction in adipose tissue weights. It was found that powdered green tea lowered the plasma total cholesterol but liver total cholesterol was unaffected. The results indicate that the hypocholesterolemic activity of powdered green tea might be due to the inhibition of the synthesis of cholesterol in the liver.
(6) Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr. 2000 ;72:1232-1234.
BACKGROUND: Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system. OBJECTIVE: We investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-h energy expenditure (EE) and fat oxidation in humans. DESIGN: Twenty-four-hour EE, the respiratory quotient (RQ), and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men. On 3 separate occasions, subjects were randomly assigned among 3 treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner. RESULTS: Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%; P < 0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P < 0.001) without any change in urinary nitrogen. Twenty-four-hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo (40%, P < 0.05). Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines. CONCLUSIONS: Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.
(7) Loest HB, Noh SK, Koo SI. Green tea extract inhibits the lymphatic absorption of cholesterol and alpha-tocopherol in ovariectomized rats. J Nutr 2002;132:1282-1288.
Evidence indicates that green tea consumption lowers the serum level of cholesterol (CH). This study was conducted to determine whether green tea lowers the intestinal absorption of CH and other lipids in ovariectomized (OX) rats. OX rats with lymph duct cannulae were infused at 3.0 mL/h for 8 h via an intraduodenal catheter with a lipid emulsion containing (14)C-cholesterol ((14)C-CH) and alpha-tocopherol (alphaTP) without (GT0) or with green tea extract standardized to 42.9 mg (GT1) or 120.5 mg (GT2) of total catechins in PBS (pH 6.5). Green tea extracts dose-dependently reduced (P < 0.05) the lymphatic absorption of (14)C-CH. The cumulative absorptions of (14)C-CH in rats infused with GT0, GT1 and GT2 were 36.3 +/- 1.1, 20.7 +/- 4.3 and 4.8 +/- 4.1% dose, respectively. The percentage distribution of esterified CH did not differ between rats infused with GT0 and GT1 (80.2 +/- 2.3% vs. 79.0 +/- 1.7%), but was significantly lower in those given GT2 (69.1 +/- 6.8%). The absorption of alphaTP also was significantly reduced by GT1 (736.5 +/- 204.9 nmol, 20.8 +/- 5.8% dose) and GT2 (281.0 +/- 190.8 nmol, 7.9 +/- 5.4% dose) compared with GT0 (1048.8 +/- 174.9 nmol, 29.6 +/- 4.9% dose). The absorption of fat was significantly increased by GT1 (862.6 +/- 151.1 micromol) but lowered by GT2 (557.9 +/- 252.2 micromol) relative to GT0 (717.7 +/- 39.1 micromol). The findings provide direct evidence that green tea has a profound inhibitory effect on the intestinal absorption of CH and alphaTP in OX rats. Whether the inhibitory effect of green tea extract is attributable to a specific catechin(s) and other components in green tea remains to be determined.
(8) Yang TT, Koo MW. Chinese green tea lowers cholesterol level through an increase in fecal lipid excretion. Life Sci 2000;66:411-423.
Lung Chen Tea, a Chinese green tea, has been found to lower serum and liver cholesterol. In this study, its dose response and mechanisms of action on cholesterol lowering in diet-induced hypercholesterolemic Sprague-Dawley rats were investigated. The activities of three major lipid metabolizing enzymes, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-Co A) reductase, cholesterol 7alpha-hydroxylase and fatty acid synthase (FAS), as well as fecal excretion of bile acids and cholesterol were examined. Lung Chen Tea administration for eight weeks significantly lowered the serum cholesterol in the 2% and 4% groups. The activities of the three enzymes were not affected by Lung Chen Tea, but the fecal bile acids and cholesterol excretions were significantly increased. These results demonstrated that Lung Chen Tea lowered plasma cholesterol by increasing fecal bile acids and cholesterol excretion. Further investigation is required to evaluate the exact mechanisms of action of Lung Chen Tea.
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