Green tea is made solely from the leaves of Camellia sinensis that have undergone minimal oxidation during processing. Tea has been cultivated for centuries, beginning in India and China. Today, tea is the most widely consumed beverage in the world, Hundreds of millions of people drink tea, and studies suggest that green tea in particular has many health benefits.
In 1994 the Journal of the National Cancer Institute published the results of an epidemiological study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly sixty percent. University of Purdue researchers recently concluded that a compound in green tea inhibits the growth of cancer cells. There is also research indicating that drinking green tea lowers cholesterol levels.
Health Benefits of Green Tea
Clinical studies that look at populations of people indicate that the antioxidant properties of green tea may help prevent atherosclerosis, particularly coronary artery disease. Population-based studies are studies that follow large groups of people over time or studies that compare groups of people living in different cultures or with different diets.
Several population-based clinical studies have shown that both green and black teas may help protect against cancer. For example, cancer rates tend to be low in countries such as Japan where people regularly consume green tea. However, it is not possible to know for sure from these population-based studies whether green tea actually prevents cancer in people. The polyphenols in tea, especially green tea, may play an important role in the prevention of cancer. Researchers also believe that polyphenols help kill cancerous cells and stop them from growing.
Research shows that green tea lowers total cholesterol and raises HDL (“good”) cholesterol in both animals and people. One population-based clinical study found that men who drink green tea are more likely to have lower total cholesterol than those who do not drink green tea.
Green tea has been used traditionally to control blood sugar levels. Green tea may help regulate glucose in the body. A few small clinical studies have found that taking a green tea extract daily lowered the hemoglobin A1c level in people with borderline diabetes.
Population-based clinical studies have shown that men who drink more than 10 cups of green tea per day are less likely to develop liver problems. Green tea also seems to protect the liver from the damaging effects of toxic substances such as alcohol. Animal studies have shown that green tea helps protect against liver tumors in mice.
Clinical studies suggest that green tea extract may boost metabolism and help burn fat. One study found that the combination of green tea and caffeine improved weight loss and maintenance in people who were overweight and moderately obese. Some researchers think that substances in green tea known as catechins are responsible for the herb’s fat-burning effect.
To date, the only negative side effect reported from drinking green tea is insomnia due to the fact that it contains caffeine. However, green tea contains less caffeine than coffee: there are approximately thirty to sixty mg. of caffeine in six – eight ounces of tea, compared to over one-hundred mg. in eight ounces of coffee
How to Brew a Cup of Green Tea
Producing the perfect cup of green tea is a tricky process. If not handled properly, those same polyphenols that provide health benefits can ruin the flavor, making the tea taste “grassy.” It’s particularly important not to overbrew green tea. While it’s best to follow the manufacturer’s instructions for each variety of green tea, here are some general instructions:
- Use one tea bag, or 2 – 4 grams of tea*, per cup.
- Fill a kettle with cold water and bring to a boil.
- After unplugging the kettle, allow it to stand for up to 3 minutes.
- Pour the heated water over the tea bag or tea, and allow it to steep for up to 3 minutes. If using a tea bag, remove the bag.
- Allow the tea to cool for three more minutes.
*One to two teaspoons, depending on the variety of green tea you are brewing.