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Green Tea and Metabolic Syndrome
Metabolic syndrome, formerly known as “Syndrome X,”
is a combination of medical disorders that increases a person’s risk of
developing coronary heart disease, atherosclerosis, stroke and type 2
diabetes. The syndrome’s own risk factors include abdominal obesity,
insulin resistance, elevated blood glucose, high triglycerides, high
total cholesterol, low HDL cholesterol, high blood pressure,
inflammation, and excessive clotting factors in the blood. When doctors
observe some or all of these symptoms in the same person, warning bells
should go off because heart disease and diabetes are on the horizon, if
not already present.
The root causes of metabolic syndrome are
overweight/obesity, lack of physical activity and genetic factors. Considering
our increasingly sedentary lifestyles and alarming rise in obesity rates, it's
no surprise that metabolic syndrome is becoming more common in the United
States, and currently affects some 50 million Americans.
The good news is that a number of studies have found that
green tea catechins can reduce many of the risk factors for metabolic syndrome.
For example, the catechins have been shown to reduce body fat,1 lower
blood sugar,2 decrease triglycerides,3 lower cholesterol,4
lower blood pressure,5 and lessen the activity of clotting factors in
the blood.6 So shouldn’t green tea, by all rights, also help ward off
metabolic syndrome, which is the sum of these parts?
According to animal studies, green tea seems to do just
that. In mice fed a high-fat diet for 16 weeks supplemented with EGCg, there was
a reduction in weight gain, percent body fat and abdominal fat, and a decrease
in insulin resistance, cholesterol and liver triglycerides.7 However,
in human trials the results have been less-than-stellar. In a group of people
with diabetes or borderline diabetes, 2 months of daily supplementation with
500mg green tea polyphenols lowered body weight, blood pressure, blood glucose
and insulin levels, among other markers of metabolic syndrome, but these results
did not differ significantly from the control group.8 In a study of
overweight or obese males taking 400 mg of EGCg twice daily for 8 weeks, no
significant changes in metabolic risk factors were seen except a reduction in
blood pressure.9 However, it could be that the doses were too small
or the treatment didn’t last long enough.
We need more well-controlled, long-term human studies of
green tea's effects on metabolic syndrome before any clear-cut conclusions can
be made. In the meantime, since green tea does seem to have beneficial
effects on the individual symptoms of metabolic syndrome, it makes sense to
continue drinking it, and often!
1Nagao
T, Komine Y, Soga S, et al. Ingestion of a tea rich in catechins leads to a
reduction in body fat and malondialdehyde-modified LDL in men. American
Journal of Clinical Nutrition 2005;81(1):122-9.
2Polychronopoulos
E, Zeimbekis A, Kastorini CM, et al. Effects of black and green tea consumption
on blood glucose levels in non-obese elderly men and women from Mediterranean
Islands (MEDIS epidemiological study). Eur J Nutr 2008;47(1):10-6.
3
Unno T, Tago M, Suzuki Y, et al. Effect of tea catechins on postprandial plasma
lipid responses in human subjects. British Journal of Nutrition
2005;93(4):543-47.
4Tokunaga
S, White IR, Frost C, et al. Green tea consumption and serum lipids and
lipoproteins in a population of healthy workers in Japan. Annals of
Epidemiology 2002;12(3):157-65.
5Yang
YC, Lu FH, Wu JS, et al. The protective effect of habitual tea consumption on
hypertension. Archives of Internal Medicine 2004;164(14):1534-40.
6Kang
WS, Lim IH, Yuk DY, et al. Antithrombotic activities of green tea catechins and
(-)- epigallocatechin gallate. Thromb Res 1999;96(3):229-37.
7Bose
M, Lambert JD, Ju J, et al. The major green tea polyphenol,
(-)-epigallocatechin-3-gallate, inhibits obesity, metabolic syndrome and fatty
liver disease in high-fat-fed mice. J Nutr 2008;138(9):1677-83.
8Fukino
Y, Shimbo M, Aoki N, et al. Randomized controlled trial for an effect of green
tea consumption on insulin resistance and inflammation markers. J Nutr Sci
Vitaminol (Tokyo) 2005;51(5):335-42.
9Brown
AL, Lane J, Coverly JH, et al. Effects of dietary supplementation with the green
tea polyphenol epigallocatechin-3-gallate on insulin resistance and associated
metabolic risk factors: randomized controlled trial. Br J Nutr
2009;101(6):886-94.
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Nadine Taylor, M.S., R.D. presents
GreenTeaLibrary.com, the most
comprehensive collection of scientific information describing the
health benefits of green tea.
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