Study confirms green tea's antioxidant benefits
By Joanne Yap, TODAY | Posted: 15 January 2008 1058 hrs

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Green tea's reputation as the drink of choice for its rich antioxidant properties has just gone up a notch.

A study conducted by researchers at the University of Arizona found that participants who were given caffeine-free green tea extracts increased the production of detoxification enzymes known as glutathione S-transferase (GST) in the body.

These enzymes are crucial in helping the body defend itself against toxic and cancer-causing compounds found in a person's genetic make-up and in the environment.

According to dietitian Charles Lew from Tan Tock Seng Hospital's Department of Nutrition and Dietetics, green tea contains compounds such as catechins that have antioxidant properties.

It may help reduce the free radical damage that is often associated with certain cancers and cardiovascular diseases.

The drink is more beneficial — compared to other beverages such as coffee, for example — because it contains six times less caffeine than the latter and is virtually calorie-free. Recent studies have also shown that the anti-inflammatory properties of green tea catechins may have a potential therapeutic value in reducing inflammation and slowing cartilage breakdown in cases of rheumatoid arthritis.

Researchers at the university studied 42 healthy individuals who were given four capsules of green tea extract every morning for a month.

They found that the GST levels in participants who had begun the study with the lowest levels of GST increased by 80 per cent, while participants who had low or moderate levels of GST to begin with experienced a slight increase in GST levels.

According to Mr Lew, green tea can be consumed every day if taken in moderation.

"There is currently no consensus on the optimal amount of daily green tea consumption as the catechin content of each type of tea varies depending on factors like where the leaves are grown, how they are processed and prepared," he said.

On average, one cup of green tea contains between 50 and 100mg of catechins.

However, Mr Lew cautioned that not everyone is suited to drinking large amounts of the beverage.

Green tea consumed with food may significantly reduce the absorption of iron from the food. Thus, those who are anaemic should avoid drinking too much of it. And people with a heart condition should check with their doctor before starting a green tea diet.

"It is important to note that antioxidant nutrients (for example, Vitamin C and Vitamin E), phytochemicals (such as catechins, carotenoids) and antioxidant enzymes (GST) work in synergy in the body.

"Thus, it's important to have a well-balanced diet, which includes at least two servings each of fruit and vegetables to ensure optimal antioxidant protection," Mr Lew advised. - TODAY/ar