An estimated 1 in 4 American adults have nonalcoholic fatty liver disease (NAFLD), a condition that could lead to liver damage, cirrhosis, or liver failure,. Because NAFLD can have such grave consequences, researchers are continually searching for ways to keep the liver lean. Scientists from the University of Connecticut have found that a common hot beverage – green tea – is capable of that very feat. While daily ingestion of green tea has been linked to an array of health benefits, this new research adds preventing NAFLD to green tea’s capabilities.
About Nonalcoholic Fatty Liver Disease
Nonalcoholic fatty liver disease (NAFLD) refers to a disease where fat accumulates in the liver of individuals who do not consume excessive amounts of alcohol. Ranging from mild and reversible to severe and irreversible, the wide spectrum of NAFLD is described below:
• Steatosis – A reversible condition, fat infiltrates the liver without evidence of inflammation or scarring.
• NASH – Nonalcoholic steatohepatitis (NASH) is accompanied by inflammation and scarring.
• Cirrhosis – Irreversible advanced scarring of the liver.
Although the exact cause of NAFLD is still unknown, evidence supports a strong connection between fat accumulation in the liver and insulin resistance. Insulin resistance occurs when the normal amount of insulin secreted by the pancreas is not able to remove sugar (glucose) from the blood into the cells for use as energy or storage for future use. One of the consequences of excessive amounts of sugar in the blood is the accumulation of fat in the body’s midsection. Thus, insulin resistance is commonly associated with fat accumulation in the liver. In extreme cases of insulin resistance, diabetes mellitus develops.
Fatty Liver Reduction Strategies
There is currently no single, effective treatment for a fatty liver. However, the following strategies have proven themselves as helpful in reducing NAFLD:
• Loss of excessive weight
• Lowering elevated cholesterol or triglycerides
• Balancing blood sugar levels
While there are a variety of prescription medications to help accomplish these goals, all healthcare experts agree that lifestyle modifications represent the best hope for reducing a fatty liver. The following strategies for weight reduction are typically suggested for those with NAFLD:
• Regular aerobic and weight-bearing exercise
• Low-fat, high fiber diet
• Alcohol abstinence
For those already working with their doctor and heeding lifestyle choices to support a lean liver, there is a common beverage now recognized to help attain a lean liver. Featured on the cover of the February 2009 issue of The Journal of Nutrition, researchers from the University of Connecticut investigated the effects of green tea on NAFLD.
After feeding genetically obese mice green tea extract for six weeks at doses equivalent to about three to seven cups of liquid green tea per day for humans, researchers found that green tea has the following effects:
• Green tea blocks the amount of fat stored in the livers of obese mice that otherwise develop severe fatty liver disease.
• Green tea improves liver function.
• Green tea reverses declines in antioxidant defenses in the liver.
While the specific process by which green tea offers these liver benefits is not yet understood, the researchers are currently exploring whether green tea:
• Interferes with fat absorption,
• Enhances the rate at which fat is used for energy by the liver and
• Blocks fat synthesis in the liver.
For those ready to embrace green tea’s benefits, lead researcher of this study Richard Bruno warns against taking green tea supplements. He advises drinking brewed green tea or eating whole green tea leaves because supplements likely contain only one of this beverage’s active ingredients.
For the estimated 40 million people in the U.S. with fatty liver disease: taking prescribed medications, engaging in regular exercise, eating a low-fat, high fiber diet and abstaining from alcohol can all help their liver. However, this new research indicates that anyone concerned with fat accumulation in his/her liver should also add drinking green tea to his/her daily routine.
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.
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