Second to water, tea is the most widely consumed drink in the world. For hundreds of years millions of people have appreciated and revered tea for its refreshing taste and its ability to complement a myriad of food flavors. The common plant, Camilla sinensis, has had an uncommon impact.
Once again tea is back in the news. Health benefits have been associated with tea for centuries, but the claims haven’t been scientifically investigated. Now over a decade of research has produced an intriguing body of evidence about the nearly miraculous health benefits of tea ranging from slowing down the aging process, boosting metabolism aiding in weight loss, to reducing the risk of cancer and heart disease.
Most potent for effectiveness appears to be green tea, which is rich in catechin polyphenols, particularly epigallocatechin gailate (EGCG). EGCG is an antioxidant with a powerful wallop.
Antioxidants are substances that scavenge free radicals; counteracting the damaging effects of oxidation in tissue. Free oxidizing radicals are a normal condition in our bodies. But environmental toxins from multiple sources like cigarette smoke, air pollution and ultraviolet radiation spike the number of these particles. Many in the scientific community believe free radicals not only contribute to the aging process, but also lead to numerous health maladies.
Antioxidants such as the polyphenols in green tea neutralize free radicals and may reduce or even help to prevent some of the damage they wreak. All types of teas possess EGCG, but green tea reportedly contains the highest concentration and is considered to be the best food source for EGCG. The secret lies in the processing method. Green tea leaves are withered and steamed preventing the EGCG compound from oxidizing. Whereas black and oolong tea leaves are fermented, resulting in the EGCG being converted into other compounds that aren’t nearly as effective.
Several studies indicate the antioxidant properties of all teas may be effective in blocking the oxidation of LDL (bad) cholesterol and increasing the HDL (good) cholesterol and thus improving artery function. Some researchers estimate drinking 3 cups of green tea a day decreases the risk of heart disease by 11 %. A Dutch study of more than three thousand men and women found the more tea consumed, the less severe the clogging of the heart’s blood vessels, especially in women.
However the FDA rejected a petition by the Tea Industry in 2006 to allow tea labels to claim green tea reduces the risk of heart disease.
The few large scale human studies which have focused on green tea’s impact on heart disease and cancer are promising, but many of those were conducted in the East where green tea is a dietary mainstay. “The outcomes are likely influenced by other life styles such as high consumption of fish and soy protein,” says cardiologist Nieca Goldberg MD, director of the New York University Women’s Heart Center.
Studies in China have shown the more green tea participants drank, the lower the risk of developing stomach cancer, esophageal, prostate, colon and pancreatic cancer. While green tea polyphenols inhibited growth of human lung cancer cells in test tubes, clinical studies have yet to demonstrate the link between tea consumption and lung cancer in people.
An article in the Scientific Daily, February 2010, reported a finding published by the Journal of Agriculture and Food Chemistry. This study done with laboratory rats confirmed that the healthful substances found in green tea do pass from the stomach and gastrointestinal tract into eye tissue. This raises the possibility that green tea may protect against glaucoma and other common eye diseases.
One area with a bright prognosis is weight loss. Green tea and its extract have been shown to boost metabolism in addition to lowering bad cholesterol. Studies suggest that drinking 3-5 cups of green tea a day burns 70 to 80 additional calories, resulting in a weight loss of 7 pounds a year. The magic is the combination of caffeine and green tea’s high content of EGCG. Caffeine has long been used in weight loss products, because it stimulates thermogenesis which is the process the body uses to produce energy. In addition EGCG also boosts thermogenesis i.e. the rate of metabolism. Furthermore there is a study suggesting EGCG may inhibit the digestion of carbohydrates by up to 25%. Both a Dutch study and a Japanese study seem to confirm the combination of green tea and caffeine improved weight loss and maintenance in overweight individuals.
Even though studies are still on going and results and statistics vary, the emerging research of the connection between tea, particularly green tea and specific health benefits is promising.
“Taken altogether the evidence certainly suggests that incorporating at least a few cups of green tea every day will positively affect your health,” says Diane McKay, PHD, a Tufts University scientist who studies antioxidants.