Green Tea Medical Benefits
Hear What Scientists Say

Green tea is booming. According to the Tea Association, 2006 was the 15th consecutive year that consumers bought more tea than ever. Retail supermarket sales neared 2 billion dollars.

Are the consumers right? Many people are already taking green tea medical benefits for granted. What do the scientists say? How much is proven? Which products are more credible?

There are many questions. But first, lets try to understand the allure of green tea.

Green tea medical benefits have been quoted in ancient Chinese texts for as long as people have been drinking it.

Pharmacist Chen Zang famously remarked:

Every medicine is the only medicine for a specific disease, but tea is the medicine for all causes.

But it is only recently that scientists have started to pay attention.

“Scientific investigations of tea compounds began less than 30 years ago, and most have been conducted in just the past 5 years,” says Hasan Mukhtar and his co-authors in the July issue of the journal Life Sciences.

"As a nutrition scientist, I consider tea as a healthy choice for three reasons:

It meets hydration needs, it has no calories and it's really rich in phytonutrients (plant-based substances) that we know provide some human health benefits."

Dr. Jeffrey Blumberg, Director of the Antioxidants Research Laboratory at Tufts University in Boston, Mass, continues to say:

"Tea has more of the catechins (a group of phytochemicals that act as antioxidants) than any food I am aware of. It is far and away the biggest, richest best source of those phytonutrients, and it's a pleasant, aromatic and flavourful beverage." 

"The most fascinating thing is, to my knowledge, there is no other natural product known that has such diversified effects," says Hasan Mukhtar, vice chair of dermatology at the University of Wisconsin-Madison.

Think of an ailment. Chances are some research suggests tea might protect against it.

Most green tea medical benefits studies are either population or laboratory based.

A population study may show that cancer is less common in countries where people drink a lot of green tea. A laboratory study is conducted in petri dishes or animals.

None of which provide conclusive evidence. The most conclusive evidence would come from human trials, but not many of them have been conducted.

It is still in the early days. After all, the scientific evidence snowballs have just begun to roll in the last 5 years.

“Drinking tea can't hurt, and, most likely, it can help,” says Mukhtar and other tea researchers. They point to the tea’s 5,000-year track record of safety.

Here are some of the more talked-about of green tea medical benefits, coming from the mouths of scientists themselves.

“Tea polyphenols, as compounds with antioxidant activity, may protect against heart disease and a variety of cancers,” Mukhtar says.

Public health nutritionist Dr. Carrie Ruxton, and colleagues at Kings College London, looked at published studies on the health effects of tea consumption.

They found clear evidence that drinking 3 to 4 cups of tea a day can cut the chances of having a heart attack. 

"Drinking tea is actually better for you than drinking water. Water is essentially replacing fluid. Tea replaces fluids and contains antioxidants so it's got two things going for it," says Dr. Ruxton.

Claire Williamson of the British Nutrition Foundation said: "Studies in the laboratory have shown potential health benefits."

The evidence in humans is not as strong and more studies need to be done. But there are definite potential health benefits from the polyphenols in terms of reducing the risk of diseases such as heart disease and cancers.

"In terms of fluid intake, we recommend 1.5-2 litres per day and that can include tea. Tea is not dehydrating. It is a healthy drink."

Mukhtar’s own research has shown that green and black tea, when substituted for drinking water, inhibits the growth of human prostate cancer cells implanted in mice.

He reported that topical application or ingestion of green tea polyphenols protects against skin cancer in mice.

“Green tea compounds positively affect genes involved in cancer susceptibility and DNA repair, although not everyone will respond equally well,” says Iman Hakim, a professor at the Arizona Cancer Center at the University of Arizona.

“An ongoing clinical trial of former and current smokers with chronic obstructive pulmonary disease has found a significant improvement in levels of HDL, or good, cholesterol in volunteers given tea as opposed to a placebo drink.”

"If tea proves to be good, it might be good to switch the kids to tea," says Hakim, who notes that tea contains less caffeine than coffee.

John Foxe, professor of neuroscience, biology and psychology at City College of the City University of New York, has conducted clinical trials of theanine, an amino acid in tea that, unlike polyphenols, is small enough to cross the blood/brain barrier.

"Probably quite a lot of people have heard tea has cardiovascular effects," says Foxe, whose work was financed by Unilever, maker of Lipton tea.

"But that's not why people drink tea. They drink it because it makes them feel good."

“People who drank a solution containing about as much theanine as 10 cups of tea were able to focus better on tasks than those who drank a placebo solution,” says Foxe at an international symposium on tea and human health in Washington.

“As little as 100 milligrams of theanine enabled people to focus better on complicated tasks, but only when consumed with 60 milligrams of caffeine — a combination found in roughly 4 cups of green tea,” says Foxe more recently.

"There was a profound synergistic effect," he says. "My take is, we're all self-medicating with this."

“Green tea seems to have more health cachet than black tea, perhaps because it has been the focus of more research. Although not as well-studied as green tea, black tea probably is at least as beneficial,” says Mukhtar.

He drinks 2 cups of black tea and 2 of green a day.

Just because drinking tea might be good for you doesn't mean adding tea extract to cereal and other foods or to dietary supplements is beneficial.

"A lot of that is gimmick," Mukhtar says of products that tout tea extract as an ingredient.

"There are not very many studies on tea supplements, yet the few we have suggest they are mimicking some of the cardio and cancer benefits established in tea studies," says Dr. Jeffrey Blumberg.

"You are going to get some of the same benefits from tea extracts, but they are not the same thing."

"I have a slight bias as a nutrition scientist. Mother Nature put a lot of different beneficial chemicals and compounds in tea so why not take advantage of all of them?" 

"By definition, supplements are 80 to 90 percent concentrated polyphenol extracts, primarily EGCG, a powerful antioxidant, but as far as I know, theanine amino acid is not in extracts, and theanine is what helps you to focus your attention on a task or relax."

A paper published in April about green tea medical benefits suggests one danger of such products with high doses of green tea extracts.

"There are quite a few case reports on liver damage due to taking supplements that contain tea extracts," says biochemist Chung Yang, a Rutgers University cancer researcher who co-wrote the paper in the journal Chemical Research Toxicology.

“Liver function returned to normal when those affected stopped taking the supplements.

In addition, studies in rodents and dogs suggest that high doses of tea catechins can damage the kidneys and intestine as well as the liver.

”Tea drinkers shouldn't worry, though", Yang emphasises: "It's very clear, there are no published reports concerning toxicity due to tea consumption." 

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