July 16th, 2007
The green tea leaf is regarded very highly around the world and has been linked to an overwhelming array of health benefits. Find out how anyone interested in supporting liver health and preventing liver fibrosis can benefit from the moderate consumption of green tea.
by Nicole Cutler, L.Ac.
In addition to preventing hardening of the liver, the following claims about green tea are backed by clinical research:
· In 1994, the Journal of the National Cancer Institute published results of an epidemiological study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly 60 percent.
· University of Purdue researchers concluded that a compound in green tea inhibits the growth of cancer cells.
· Numerous studies demonstrate that green tea lowers total cholesterol levels, as well as improving the ratio of HDL (good) cholesterol to LDL (bad) cholesterol.
The Secret Ingredient
Green tea’s many health benefits are owed to its richness in catechin polyphenols, particularly epigallocatechin gallate (EGCG). A powerful antioxidant, EGCG kills cells gone awry, without harming healthy tissue. In addition to lowering LDL cholesterol levels, EGCG has been shown to inhibit the formation of harm-causing blood clots.
At the 2006 Annual Association for the Study of Liver Diseases meeting, researchers revealed proof that EGCG contributes to the inhibition of two liver disease progression indicators, oxidative stress and inflammation. Two separate studies prompted this conclusion as described below:
Study 1 = Mice were injected with the known liver toxin, carbon tetrachloride, to artificially induce inflammation and liver cell oxidation. Some of these rodents also received EGCG injections. The group receiving EGCG had markedly reduced liver inflammation and damage than the group receiving only carbon tetrachloride. Researchers concluded that EGCG slowed artificially induced liver fibrosis.
Study 2 = Laboratory rats were fed a diet high in fat to simulate non-alcoholic fatty liver disease (NAFLD). A portion of the rats with simulated NAFLD were also given EGCG. The NAFLD rats showed significant fatty changes, necrosis and liver inflammation. However, those receiving EGCG experienced significantly less liver injury.
Based on the results of both studies, the researchers suggested that green tea polyphenols may be a useful therapeutic agent for hepatic fibrosis and a useful supplement for NAFLD.
More About Polyphenols
Green tea’s ingredients have been the focus of liver health research for years:
· In the October 2005 issue of International Journal of Molecular Medicine, Japanese researchers found that EGCG inhibited collagen production and suppressed collagenase activity, making it of therapeutic potential for treating liver fibrosis.
· In the November 2003 edition of American Journal of Physiology, Gastrointestinal and Liver Physiology, researchers concluded that polyphenols from green tea scavenge oxygen radicals and prevent activation of stellate cells, thereby minimizing liver fibrosis.
· In the September 2004 edition of American Journal of Clinical Nutrition, researchers concluded that green tea polyphenols reduce the severity of liver injury in association with lower concentrations of lipid peroxidation and proinflammatory nitric oxide-generated mediators.
Green is Great
There are many kinds of tea, each with its own set of characteristics. Green, oolong and black teas all come from the leaves of the Camellia sinensis plant. Unlike oolong and black tea leaves, green tea leaves are steamed, preventing the EGCG compound from being oxidized. By contrast, black and oolong tea leaves are made from fermented leaves. The fermentation converts EGCG into other compounds that are not nearly as effective in preventing and fighting various diseases.
In the past, there have been cautions against the regular consumption of green tea due to its caffeine content. Containing less caffeine than the average small cup of coffee, which contains 100 mg of caffeine, a similarly sized cup of green tea has between 30 and 60 mg. Despite this comparatively low caffeine content, individuals sensitive to caffeine may still experience difficulty sleeping when consuming green tea.
While confirming green tea’s liver protective properties, a 2006 University of Toronto study also suggests that excessive amounts of green tea’s polyphenols can actually harm the liver. Although researchers concluded that drinking green tea can help protect the liver from injury, they also cautioned against concentrating polyphenols into an EGCG pill.
The preparation of green tea also appears to make a therapeutic difference. In order to extract tea’s enormous health benefits, nutrition expert Paul Pitchford reminds us not to make it too strong. In fact, Pitchford says, “The second infusion of the tea leaves is often the most appreciated for its subtlety because the tannic acids in the tea do not overpower the infusion. Much of the negative value of tea will not exist in this milder version.”
Experts claim that when brewed to be strong, the polyphenols providing green tea’s health benefits can ruin the tea’s flavor and make it gassy. The following suggestions provide a general guide for brewing an optimal cup of green tea:
· Use one tea bag, or 2 – 4 grams of tea, per cup.
· Fill a kettle with cold water and bring to a boil.
· Remove kettle from the heat and allow it to stand for up to 3 minutes.
· Pour the heated water over the tea bag or tea leaves, 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.
While it is prudent to maintain moderation in all that we ingest, there is plenty of proof directing us to green tea consumption. Drinking properly prepared green tea is a simple and effective way to naturally protect against liver fibrosis.
Chen JH, Tipoe GL, et al., Green tea polyphenols prevent toxin-induced hepatotoxicity in mice by down-regulating inducible nitric oxide-derived prooxidants, American Journal of Clinical Nutrition, September, 2004.
Guyton KZ, Kensler TW, Prevention of liver cancer, Current Oncology Reports, November, 2002.
Nakamuta, M, et al., Epigallocatechin-3-gallate, a polyphenol component of green tea, suppresses both collagen production and collagenase activity in hepatic stellate cells, International Journal of Molecular Medicine, October 2005.
Pitchford, Paul, Healing with Whole Foods, North Atlantic Books, Berkeley, CA, 1993.
Zhong Z, Froh M, et al., Polyphenols from Camellia sinenesis attenuate experimental cholestasis-induced liver fibrosis in rats, American Journal of Physiology, Gastrointestinal and Liver Physiology, November, 2003.
www.chinesefood.about.com, The Miracle of Green Tea, About Inc., 2006.
www.hivandhepatitis.com, Can Green Tea Help Ameliorate Liver Fibrosis?, hivandhepatitis.com, 2006.
www.medicalnewstoday.com, Green Tea Polyphenols May Cause Liver Damage In High Doses, MediLexicon International, Ltd., February 2006.
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