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Drink Up? Study Re-evaluates the Antioxidant Benefits of Green Tea.

Do we really need to start brewing cups of green tea? On March 25, 2004 the American Heart Association’s journal, Circulation, published the results of a study exploring the effects of the antioxidant found in green tea on present and future arterial plaque buildup. As heart disease and stroke remain the No. 1 and No. 3 causes of death among Americans determining the effectiveness of antioxidants on the prevention and elimination of plaque buildup in arteries is crucial. Evidently, the timing of antioxidant treatment is key.

By: Lesley Michael

May 27th, 2004

Browsing through your local drugstore you’ve probably seen plenty of products, supplements, and literature describing the health benefits of antioxidants. Is this just a smart marketing tactic or can antioxidants actually help prevent cardiovascular diseases and cancers? While breakfast cereals, fresh produce, and ketchup bottles now boast colorful labels denoting the presence of Vitamins A, C, and E, lycopene, and beta-carotene, do these antioxidants deserve all the limelight? 

First things first…a crash course on antioxidants.

Naturally found in brightly colored fruits and vegetables, nuts, and grains, antioxidants remain the subject of many research studies, as their specific benefits have yet to be consistently supported. The National Cancer Institute explains that antioxidants prevent cellular damage to DNA and other molecules because they block the harmful effects of free radicals.

Free radicals are the by-products of natural cell-processes in which molecules are left unstable and without complete outer-electron shells. For example, after normal cellular metabolism a leftover oxygen particle (the most common free radical) will try to steal electrons from other molecules, causing damage and destruction. The formation of free radicals is also attributed to exposure to tobacco smoke and radiation. This free radical damage irreversibly builds up and can lead to major health risks including cancers and diseases affecting the organs of the body.

Antioxidants successfully bind to these free radicals and neutralize them before damage is caused to surrounding molecules

Researchers at Cedars-Sinai Medical Center designed a study that evaluated the effects of epigallocatechin-3-gallate (EGCG) on early and late stages of plaque buildup in the arteries of mice predisposed to increased levels of plaque formation. EGCG is a potent antioxidant found in green tea and is effective in protecting cells and DNA from damage linked to heart disease and cancers.

Cardiovascular diseases are often times treated with EGCG because it is thought to prevent oxidation in the arteries, which produces free radicals and eventually leads to the growth of plaque deposits and a greater incidence of heart disease.

Because past human trials have only looked at the effects of antioxidants after significant plaque buildup had already occurred, scientists at Cedars-Sinai Medical center proposed that antioxidants may only have effects on preventing future buildup and not on eliminating plaque already produced. The team’s cardiologist, Kuang-Yuh Chyu, MD, PhD, explained to HealthDay News, "Most animal experiments evaluating the effects of antioxidants are started when the animals are young. Randomized clinical trials typically enroll adult patients with varying stages of plaques." Chyu continued, "This discrepancy supports speculation that antioxidant treatment affects early but not later stages of plaque development."

Plaque levels were assessed and compared 5, 21 and 42 days after the animals were inflicted with an injury to their main artery, producing significant levels of plaque buildup. After three weeks, animals treated with the green tea extract had 55% less plaque than those animals not given EGCG. By six weeks, they had 73% less plaque. However, the antioxidant introduced to the matured plaque buildup did not erase previous damage, it only inhibited growth.

Thus the study concluded that therapeutic benefits of antioxidants are only present when introduced during the earliest stages of plaque buildup in arteries. Instead of treating existing diseases with antioxidant therapy, it is beneficial to follow a preventative approach and begin incorporating antioxidants into your diet before serious problems arise.

Further studies including human subjects that examine the role of antioxidants are expected to be complete within the next 2-5 years. More information on these studies is available at ClinicalTrials.gov.

In the meantime…drink up and enjoy a nice, hot cup of green tea!

References:

“Differential Effects of Green Tea–Derived Catechin on Developing Versus Established Atherosclerosis in Apolipoprotein E–Null Mice,” Circulation: Journal of the American Heart Association. May 25, 2004.

“Green Tea Helps Keep Arteries Clear,” HealthDay News. May 24, 2004.

The National Cancer Institute’s Fact Sheet on Antioxidants. January 8, 2003.

“Antioxidant chemistry if green tea catechins,” Clinical Research in Toxicology. 13(9):801-10, September 2000.