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The Truth about Green Tea

A Health Powerhouse or Mostly Hype?
  -- By Becky Hand, Licensed and Registered Dietitian
Whether you drink it as a hot beverage to ward off Old Man Winter or iced to cool off on a hot summer day, tea is an invigorating drink that people around the world consume in copious amounts. In America alone, each person drinks approximately 155 cups of tea per year! And as researchers discover more health benefits from those little leaves, tea sales continue to climb. But we're not just drinking tea; its extracts are becoming popular supplements and additions to other foods and drinks.

If you drink tea because you enjoy the taste, great. But if you're buying foods or supplements that contain tea extracts, thinking they'll help lower your risk for cancer and heart disease, speed your metabolism, or help you lose weight as many products claim, think again. Let's look at what research (and common sense) really tells us about tea, tea extracts and supplements, and what they can—and can't—do for your health.

First Things First: What is Tea?
Technically, only one plant provides the leaves to make what we know as tea: Camellia sinensis. The difference in the flavor, color, and name of the tea depends on how the leaves are processed. There are four basic types of tea: Many other hot and cold drinks are referred to as "tea," but unless they are made with Camellia sinenesis, they are not true teas; they are herbal teas (made from a variety of other plants, flowers and herbs). Some herbal teas may offer health benefits, but you cannot assume that the health benefits of one type of tea apply to any other variety. <pagebreak>

Components of Tea: Catechins and Caffeine
Flavonoids are dietary compounds found in tea and other foods such as wine, cocoa, fruits and vegetables. Flavonoids determine the color and taste of food and may be involved in healthy body functions. The average U.S. adult consumes 189.7 milligrams of flavonoids each day, most of which (157 mg to be exact) come from tea. While there is currently no recommendation for flavonoid consumption, experts are in the initial stages of discussion regarding recommendations for these dietary components. Tea contains approximately 100-300 milligrams of flavonoids per serving, depending on the type of tea. The main type of flavonoids found in tea are catechins. Because the green tea variety is less processed, it contains more catechins than black tea does. Therefore green tea and green tea extracts have received the most research regarding possible health benefits and will be the focus of this particular article. Research has primarily investigated the health benefits of catechins such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).

Green tea also contains 2% to 4% caffeine or about 10-80 milligrams per cup. (For reference, a cup of regular coffee contains 95 mg of caffeine, while 1 oz. of dark chocolate contains 23 mg.) Caffeine has also been the topic of many research studies regarding the health benefits of green tea.

Health Benefits of Green Tea: What the Research Really Shows

The research to date indicates that green tea is likely effective for: Research to date shows that green tea might be effective for:
Currently, there is not enough evidence to say that green tea has the following health benefits: <pagebreak>
More research is needed in the areas of cardiovascular disease, hypertension, and osteoporosis before we can make any claims about green tea's effects on these conditions. <pagebreak>

How to Get the Health Benefits of Green Tea
While green tea is rich in antioxidants, studies have shown that the bottled varieties of tea don't even come close to the antioxidant levels you'll find in home-brewed green tea. Researchers found as few as 3 milligrams of flavonoids in premade (bottled) teas, compared with up to 150 milligrams in the kind that is brewed at home. To get the most of your tea, steep it at home for 6-10 minutes, then enjoy it either hot or iced. (This will save you money, too!)

It should be noted that green tea extracts and green tea supplements have not been as widely studied as the fresh-brewed beverage itself has been. Most research on the health benefits of tea applies to tea drinking alone. Whether any of these benefits can be achieved by taking a pill or extract, drinking an energy drink with EGCG added, or eating a packaged food product that contains extracts of green tea is questionable. Many of these products contain so little green tea that they'd offer no benefit at all. Others may contain high levels that can be unhealthy (see warnings below). Your best bet is to stick with a fresh-brewed cup of tea and not spend extra on costly functional foods or supplements.

Warnings with Green Tea and Green Tea Extracts
Beverage experts suggest no more than 5 cups (40 ounces) of tea daily for a healthy adult, for a maximum intake of no more than 400 milligrams of caffeine daily. While green tea is likely safe for most adults in moderate amounts, too much green tea can bring about side effects due to the caffeine content. Side effects can vary from mild to moderate headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, and dizziness. Excessive consumption of tea can also bring on stomach upset or constipation. And believe it or not, extremely high doses of green tea can be fatal! Here are a few additional cautions of which to be aware. In 2006, the FDA rejected a petition to allow a new "health claim" on food packaging labels regarding green tea usage and various risk factors of heart disease. For a company to put a health claim like this on a package requires substantial scientific evidence and the FDA felt the research was non-conclusive. However, "function" claims are allowed. A function claim describes how a food or food ingredient affects the body, but cannot mention a disease. Function claims are not pre-approved by the FDA and do not require scientific evidence, and they appear constantly on food labels, even when there is no evidence to back them up. You may have seen numerous function claims about green tea on a variety of products that contain green tea, green tea extracts, and EGCG. Beware of these products! Excessive intake of green tea extracts used in supplements, and added to foods and beverages may bring about liver toxicity and other liver problems in some cases. Talk to your doctor before using any food product, beverage or supplement that has been fortified with green tea extracts or EGCG.

Brew Up a Cup
Taken all together, there does appear to be some health benefits in that little cup of green tea. A few cups a day could have a positive effect on your health. It's probably not going to cure any disease, and should not be consumed as a drug; but as part of your overall healthy diet, drink up!

Sources:
Degradation of Green Tea Catechins in Tea Drinks, from Journal of Agriculture and Food Chemistry
Effect of Green Tea Catechins with or without Caffeine on Anthropometric Measures: A Systematic review and Meta-Analysis, from American Journal of Clinical Nutrition
Estimated Dietary Flavonoid Intake and Major Food Sources of U.S. Adults, from The Journal of Nutrition
Green Tea, from Natural Medicines Comprehensive Database