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Green Tea Extract Lowers Cholesterol in Human Trials
Adapted from Alternative Medicine Review, August, 2003Tea consumption has long been associated with decreased risk of cardiovascular disease, but only recent research has begun to suggest specific biochemical mechanisms that give rise to this benefit. Demonstration of how specific metabolic pathways and cell receptors in the body are necessary to demonstrate scientifically reliable proof that specific chemicals found in tea can reduce cholesterol and improve the ratio of good (HDL) cholesterol to bad (LDL) cholesterol in human beings.
Epidemiologic studies suggest that drinking multiple cups of tea per day lowers low-density lipoprotein cholesterol (LDL), early trials of tea drinking and administration of green tea extract have failed to show any direct impact on lipids and lipoproteins in humans. A research group headed by DJ Maron set out to make this connection clear by studying the impact of a theaflavin-enriched green tea extract on the lipids and lipoproteins of subjects with mild to moderate levels of high cholesterol.
Maron and his team conducted a double-blind, randomized, placebo-controlled, parallel-group trial using outpatient clinics in 6 urban hospitals in China. A total of 240 men and women 18 years or older on a low-fat diet with mild to moderate levels of high cholesterol were randomly assigned a daily capsule containing theaflavin-enriched green tea extract (375 mg) or placebo for 12 weeks. Individuals were then tested for age-adjusted changes in total cholesterol, LDL-C, high-density lipoprotein cholesterol (HDL-C), and triglyceride levels.
After 12 weeks levels of total cholesterol were significantly reduced, and the ratio of HDL and LDL cholesterol were improved to a significant degree. No significant adverse events were observed.
Maron and his researchers concluded that the theaflavin-enriched green tea extract studied was shown an effective adjunct to a low-saturated-fat diet to reduce LDL-C in hypercholesterolemic adults and was well tolerated.
In another Australian study Senior Research Scientist Dr Paul Roach found evidence to support the conclusion that the green tea's high concentration of strong antioxidants catechins increase the liver's LDL receptors, a major mechanism for cholesterol control. This study suggests more than one mechanism may play a role in reducing high cholesterol in human beings.
Other research has shown that the catechin polyphenol in green tea called epigallocatechin gallate (EGCG) is the component that reduces the levels of LDL, also known as bad cholesterol. Aside from reducing cholesterol levels, drinking green tea also raises the levels of the good cholesterol known as HDL. The health benefit of green tea is apparent in one population-based study. It found that men who drink green tea are more likely to have lower levels of total cholesterol compared to those who do not drink green tea.
Studies have also shown the health benefit of green tea when it comes to the reduction of LDL levels. One study revealed that in male smokers, green tea had a considerable effect on their levels of harmful cholesterol. The study showed that the male smokers who drank green tea considerably lowered their blood levels of bad cholesterol.
While more research must be conducted to further confirm the conclusions of these, the results of this study are one more clinical trial demonstrating the efficacy of drinking green tea in lowering the risk of high cholesterol and cardiovascular disease. As always, those who enjoy drinking green tea can take comfort in the results of this study as offering further support for the health benefits of drinking green tea. Individuals with high cholesterol levels may consider adding green tea to a diet of low-saturated fats.
ReferencesCholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial - Recently Published Abstracts - Author Abstract
Alternative Medicine Review, August, 2003 by DJ Maron, GP Lu, NS Cai
Maron D J, Lu GP, Cai NS, et al. Arch Intern Med 2003;163:1448-1453.
Media Release - Ref 2000/273 - Oct 18 , 2000, CSIRO Human Nutrition, Adelaide BC.