Green tea is made solely with the leaves of Camellia sinensis. It is indigenous to China but is now associated with many cultures throughout Asia. There are three main varieties of tea — green, black, and oolong. The difference between the teas is in their processing. Green tea is made from unfermented leaves and reportedly contains the highest concentration of powerful antioxidants called polyphenols. These compounds have been linked to lower rates of a number of diseases and conditions including oxidative stress, heart disease, digestive problems and cancer. They may even help you lose weight. Long used as part of traditional Chinese medicine, increasing scientific analysis mean that the benefits of green tea are now becoming well known in the West.
Benefits of green tea
Today, tea is the most widely consumed beverage in the world, second only to water. Billions drink tea, and studies suggest that the benefits of green tea, in particular, are substantial and widespread. The flavonoids (antioxidants) in green tea scavenge free radicals — damaging compounds in the body that alter cells, tamper with DNA, and can trigger the development of cancer. Free radicals occur naturally in the body, but environmental toxins also give rise to these damaging particles. Several studies have found that free radicals contribute to the aging process (called the “free-radical theory of aging) well as the development of a number of other health problems, including cancer and heart disease. In traditional Chinese and Indian medicine, practitioners used green tea as a stimulant, diuretic (to promote the excretion of urine), astringent (to control bleeding and help heal wounds), and to improve heart health. Other traditional benefits of green tea include treating flatulence (gas), regulating body temperature and blood sugar, promoting digestion, and improving mental clarity.
The healthy benefits of green tea are largely attributed to polyphenols. Polyphenols are chemicals with potent antioxidant properties. In fact, the antioxidant effects of polyphenols appear to be greater than that of vitamin C. The polyphenols in green tea also give it a somewhat bitter flavor. Polyphenols contained in teas belong to a class of compounds called catechins. Green tea contains six primary catechin compounds: catechin, gallaogatechin, epicatechin, epigallocatechin, epicatechin gallate, and apigallocatechin gallate (also known as EGCG). EGCG is the most studied polyphenol component in green tea and also the most active. Green tea also contains alkaloids including caffeine, theobromine, and theophylline. These alkaloids provide green tea’s stimulant effects. L-theanine, an amino acid compound found in green tea, has been studied for its calming effects on the nervous system.
- Boost the metabolism: Clinical studies have suggested that green tea extract may boost metabolism and help burn fat. A study performed at Birmingham (UK) University, showed that average fat oxidation rates were 17% higher after ingestion of green tea extract than after ingestion of a placebo. Other studies have shown that consumption of green tea lowered blood pressure and cholesterol. Some researchers speculate that the caffeine and the polyphenols, specifically the catechins, are responsible for the herb’s fat-burning effects.
- Lowers cholesterol: Research shows that the benefits of green tea lower total cholesterol and raises High-Density Lipoprotein (HDL) or “good” cholesterol. Results from one animal study suggest that polyphenols in green tea may block the intestinal absorption of cholesterol and promote its excretion from the body. In another small study of male tobacco smokers, researchers found that the benefits of green tea significantly reduced blood levels of harmful Low-Density Lipoprotein (LDL) or “bad” cholesterol.
- Stabilizes blood sugar: Green tea has been used traditionally to control blood sugar levels in the body. Animal studies suggest that green tea may help prevent the development of Type 1 diabetes and slow its progression once it has developed. People with type 1 diabetes produce little or no insulin, a hormone that converts glucose (sugar), starches, and other foods into energy needed for daily life. Green tea may help regulate glucose in the body, and can be a healthy staple of a diabetic diet.
- Reduces inflammation: The benefits of green tea may help reduce inflammation associated with Crohn’s disease and ulcerative colitis, the two types of Irritable Bowel Disease (IBD).
- Atherosclerosis: The antioxidant benefits of green tea may help prevent atherosclerosis and, in particular, coronary artery disease, according to studies. Researchers have found that the benefits of green tea reduce the risk of heart disease by lowering cholesterol and triglyceride levels. In fact, researchers estimate that the rate of heart attack decreases by 11% with consumption of 3 cups of tea per day.
- Cancer: Clinical studies suggest that the polyphenols in tea, especially green tea, may play an important role in the prevention of cancer. Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells, although studies on humans have had conflicting findings. Green tea polyphenols have been shown to inhibit the growth of human lung cancer cells in test tubes, few clinical studies have looked at the link between drinking green tea and lung cancer in people.
- Liver disease: Studies have found that men who drink more than 10 cups of green tea per day are less likely to develop disorders of the liver. The benefits of green tea also seem to protect the liver from the damaging effects of toxic substances such as alcohol. A study on mice has shown that green tea helps protect against the development of liver tumors. Results from several studies suggest that one of the polyphenols present in green tea, known as catechin, may help treat viral hepatitis (inflammation of the liver from a virus).
- Inflammatory Bowel Disease (IBD): The benefits of green tea may help reduce inflammation associated with Crohn’s disease and ulcerative colitis, the two types of IBD. If green tea proves to be helpful for preventing colon cancer, this would be an added benefit for those with IBD because they are at risk for colon cancer. However, studies that examine the link between green tea and colorectal cancer have been conflicting – some find that green tea lowers the risk, while others find it has no benefit, and a few find it slightly increases the risk.
- Diabetes: Green tea has been used traditionally to control blood sugar in the body. Green tea is known to help prevent the development of type 1 diabetes and slow the progression once it has developed. People with type 1 diabetes produce little or no insulin, a hormone that converts glucose (sugar), starches, and other foods into energy needed for daily life. The benefits of green tea may help regulate glucose in the body. A few small clinical studies have found that daily supplementation of the diet with green tea extract powder lowered the hemoglobin A1C level, a marker for blood glucose levels, in individuals with borderline diabetes.
- Sensitivity to caffeine: Green tea has about the same caffeine as black tea, or about 24-40 mg per 8 oz cup. (The exact amount depends on the type of tea, how long it is steeped for, etc). Some people are more sensitive to caffeine. If your caffeine consumptions totals more than 500 mg per day, according to the Mayo Clinic, you may want to consider cutting back.
- Gluten intolerance: Green tea is gluten free, however some manufacturers may expose it to gluten products during the manufacturing. Trader Joe’s, Teavanna, Celestial Seasonings, Yogi Pure Green Decaf, Tazo, and Salada Green Tea all claim to be gluten-free.
Green tea has been used for thousands of years for its calming, restorative and medical benefits as part of traditional Chinese medicine. Growing scientific research have shed light on its many beneficial health benefits. Green tea is a stimulant, and contains caffeine, so you should be careful not to drink too much, especially before bed, or if you are pregnant.