| The Benefits of Green Tea |
By now you have heard about the potential health benefits of drinking green tea. Unlike many other natural supplements, there has actually been a great deal of research going on regarding its benefits. Green, black and oolong teas all come from the same plant. Their differences lie in how long they are fermented for. Black tea is fermented the longest. Oolong tea is partially fermented and green tea is not fermented at all.1 Many of the health benefits of green tea are thought to be partially due to the fact that green tea is not fermented, leaving the plant's beneficial chemicals in tact. However, many of the same health benefits that have been attributed to green tea have also been linked to black and oolong teas as well. Heart and Blood Vessel Benefits There is evidence available that suggests drinking green tea is associated with such benefits as decreasing the risk of stroke, improving the blood cholesterol panel and decreasing the incidence of blood clots. One study showed the more green tea consumed, the better that person's cholesterol panel was likely to be.2 This study is supported by others that suggest that at least one 8 ounce cup of green tea daily may be needed to see a benefit in your cholesterol panel. Drinking over 20 ounces (almost three 8 ounce cups) Despite these studies that suggest drinking green tea can benefit cardiovascular health, there are studies that did not show an improvement. These were smaller, short-term studies. For this reason, the FDA concluded that there is not enough evidence to allow green tea producers to claim these benefits on their label. Cancer Prevention There are some studies that suggest that green tea may reduce the risk of certain cancers. Unfortunately, many of these studies were poorly conducted. Other studies are conflicting. There is one large study that was much more well-designed that showed that drinking black tea reduced the risk of ovarian cancer. Two cups daily was needed to reduce the risk of this cancer in half.5 Another study suggested that drinking 10 cups of green tea daily was associated with a decreased risk of gastric cancer.1 The FDA's official stance is that based on the evidence, it is unlikely that green tea consumption reduces the risk of breast or prostate cancer. They also concluded that there is not enough evidence to allow producers to make any claims related to cancer prevention on the label of any green tea product. Obesity There has been evidence that suggests that EGCG, one of the substances in green tea, may increase metabolism and suppress appetite.6 More studies are still needed to confirm these findings. You will find green tea or EGCG in many weight loss supplements. Diabetes Japanese studies suggest that consuming green tea may help decrease the risk of type 2 diabetes. At least six cups daily was associated with a two-thirds reduction in risk of type 2 diabetes versus those who consumed one cup or less.7 It is unclear if it is the caffeine content or another constituent of green tea that is responsible for this effect. It is probably not the caffeine as other studies have shown that large amounts of caffeine can be associated with worsening of insulin resistance and blood sugar control in diabetics.1 Osteoporosis Green tea may help strengthen bones and prevent osteoporosis. More studies are needed but preliminary data shows that 10 years of green tea consumption is associated with higher bone mineral density. This is an interesting finding in that many other studies have shown that caffeine may be associated with bone loss. Perhaps the effects of the good chemicals in green tea are enough to overcome its caffeine content? Only after further studies on the subject will be know for sure. What About Side Effects and Drug Interactions? There are few side effects reported with green tea. There have been a few cases of liver toxicity while taking green tea extracts in pill form, however, it is unclear if the green tea was the cause of the toxicity.1 People who are prone to bleeding or are taking 'blood thinners' should use caution when consuming green tea. Green tea may inhibit your blood's ability to clot, putting some people at risk for bleeds. Green tea does have caffeine in it which can lead to irritability, nervousness, headaches and anxiety in some people. When taken with certain other medications (like cimetidine (Tagamet), Diflucan, or verapamil) the effects of any caffeine that you have ingested can be amplified.1 Green tea may interact with other medications such as theophylline and warfarin (Coumadin). Green tea can increase theophylline levels in the body. Green tea also has a high vitamin K content which can affect how well your warfarin works. If you are taking theophylline or warfarin and take green tea, it is extremely important that you consult with your doctor so that the doses of these medications can be adjusted if needed.1 Conclusion Preliminary data seems to suggest that green tea consumption may benefit a variety of conditions. While more evidence is needed, green tea appears to be fairly safe. Because of the potential for liver toxicity with green tea supplements in the pill form, it may be best to stick with green tea beverages for now. Beware of green teas that combine other herbal ingredients that have an unknown safety profile. Certain other herbs that are considered safe by the FDA include chammonile, spearmint, and peppermint.1
Author: Christi Larson, Pharm. D. Dr. Larson is a Clinical Infusion Pharmacist, author of Empowered Medicine; A Guide for Consumers and creator of www.empoweredmedicine.com. You can read more about her by visiting www.EmpoweredMedicine.com and clicking on the 'About Us' tab. EmpoweredMedicine.com is committed to providing evidence-based medical information.
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