Green tea extract given to lab rats over a 10-week span increased the amount of time the animals could swim before becoming exhausted by as much as 24%.

Green tea’s catechins appear to stimulate the use of fatty acids by liver and muscle cells. In muscle cells, the ability to burn more fat translates into a reduction in the rate at which glycogen, the form in which carbohydrates are stored for ready access in muscle, is used up, thus allowing for longer exercise times. Green tea’s effect on muscle cells’ ability to take in and burn fatty acids, speeding up fat breakdown, is also thought to be the reason why it helps weight loss.

The idea for the experiment came from the fact that skeletal muscles utilize carbohydrates, lipids (fats) and amino acids (protein) as energy sources, but the ratio in which they are used varies with the intensity and type of the exercise, and the level of the individual’s fitness. During endurance exercise, the use of too much carbohydrate is undesirable because it triggers insulin secretion, which, in turn, both inhibits the burning of fatty acids and stimulates lactic acid production. (Lactic acid buildup is what causes that sore achy feeling in your muscles when you exercise.) Conversely, enhanced availability and utilization of free fatty acids reduces carbohydrate utilization, which in turn spares glycogen (the form in which carbohydrates are stored in muscle for quick use) and suppresses lactic acid production, resulting in an increase in endurance.”

Drinking a single cup of green tea before exercise, however, will not be effective. One single, higher “dose” of green tea did nothing to improve lab rats’ performance. The animals had to receive green tea daily, and endurance increased gradually over the 10 weeks of the study.

To match the beneficial effect on test animals’ endurance capacity seen in the experiments, the researchers estimate a 165-pound athlete would need to drink about 4 cups of green tea daily.

A new study shows high doses of the green tea ingredient — known as epigallocatechin-3-gallate (EGCG) — significantly reduced the formation of beta-amyloid proteins in the brains of mice that were altered to develop Alzheimer’s disease. An abnormal buildup of beta-amyloid plaque in the brain is implicated in the nerve damage and memory loss seen in Alzheimer’s disease.

EGCG is one of a group of antioxidants called flavonoids found in plants. They have been linked to a variety of health benefits seen in diets rich in fruits and vegetables, such as protecting against cancer or reducing the risk of heart disease.

Antioxidant May Protect Brain

In the study, published in the Journal of Neuroscience, researchers studied the effects of treating mice genetically altered to develop Alzheimer’s disease with high doses of the green tea antioxidant.

After several months of daily injections of EGCG, the results showed that the nerve cells of treated mice generated as much as 54% fewer beta-amyloid protein than nontreated mice nerve cells.

“The findings suggest that a concentrated component of green tea can decrease brain beta-amyloid plaque formation,” says researcher Jun Tan, PhD, MD, director of the Neuroimmunology Laboratory at the University of South Florida, in a news release. “If beta-amyloid pathology in this Alzheimer’s mouse model is representative of Alzheimer’s disease pathology in humans, EGCG dietary supplementation may be effective in preventing and treating the disease.”

The US Cancer institute has published fact sheet entitled ‘tea and cancer prevention’, the key points are featured below. It seems to refelct very positively that green tea consumption aids cancer prevention.

Tea drinking is an ancient tradition dating back 5,000 years in China and India. Long regarded in those cultures as an aid to good health, researchers now are studying tea for possible use in the prevention and treatment of a variety of cancers. Investigators are especially interested in the antioxidants-called catechins-found in tea.

1. What are antioxidants?

The human body constantly produces unstable molecules called oxidants, also commonly referred to as free radicals. To become stable, oxidants steal electrons from other molecules and, in the process, damage cell proteins and genetic material. This damage may leave the cell vulnerable to cancer. Antioxidants are substances that allow the human body to scavenge and seize oxidants. Like other antioxidants, the catechins found in tea selectively inhibit specific enzyme activities that lead to cancer. They may also target and repair DNA aberrations caused by oxidants (1).

2. What is the level of antioxidants found in tea?

All varieties of tea come from the leaves of a single evergreen plant, Camellia sinensis. All tea leaves are picked, rolled, dried, and heated. With the additional process of allowing the leaves to ferment and oxidize, black tea is produced. Possibly because it is less processed, green tea contains higher levels of antioxidants than black tea.

Although tea is consumed in a variety of ways and varies in its chemical makeup, one study showed steeping either green or black tea for about five minutes released over 80 percent of its catechins. Instant iced tea, on the other hand, contains negligible amounts of catechins (1).

3. What are the laboratory findings?

In the laboratory, studies have shown tea catechins act as powerful inhibitors of cancer growth in several ways: They scavenge oxidants before cell injuries occur, reduce the incidence and size of chemically induced tumors, and inhibit the growth of tumor cells. In studies of liver, skin and stomach cancer, chemically induced tumors were shown to decrease in size in mice that were fed green and black tea (1, 2).

4. What are the results of human studies?

Although tea has long been identified as an antioxidant in the laboratory, study results involving humans have been contradictory. Some epidemiological studies comparing tea drinkers to non-tea drinkers support the claim that drinking tea prevents cancer; others do not. Dietary, environmental, and population differences may account for these inconsistencies.

Two studies in China, where green tea is a mainstay of the diet, resulted in promising findings. One study involving over 18,000 men found tea drinkers were about half as likely to develop stomach or esophageal cancer as men who drank little tea, even after adjusting for smoking and other health and diet factors (3). A second study at the Beijing Dental Hospital found consuming 3 grams of tea a day, or about 2 cups, along with the application of a tea extract reduced the size and proliferation of leukoplakia, a precancerous oral plaque.

5. Is NCI evaluating tea?

National Cancer Institute (NCI) researchers are also investigating the therapeutic use of green tea. One recently completed but unpublished NCI trial studied the antitumor effect of green tea among prostate cancer patients. The 42 patients drank 6 grams of green tea, or about 4 cups, daily for four months.

Other ongoing NCI studies are testing green tea as a preventive agent against skin cancer. For example, one is investigating the protective effects of a pill form of green tea against sun-induced skin damage while another explores the topical application of green tea in shrinking precancerous skin changes.