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What’s in Your Green Tea?

(2014-04-29 13:44:28) 下一个
http://articles.mercola.com/sites/articles/archive/2013/07/03/green-tea-benefits.aspx

Green tea, prized for many generations in China, Japan and even Britain, has made a name for itself in the US, where many now drink it daily due to its many associated health benefits.

However, while green tea is recognized as an abundant source of epigallocatechin-3-gallate (EGCG), a catechin polyphenol, and other antioxidants, not all green teas are created equal.

If you’re drinking green tea hoping to increase your antioxidant levels, you should know that some green tea brands contain very little antioxidants, while others may contain significant amounts of lead.

One Variety of Tea Tested Contained Almost No EGCG

EGCG is easily the most talked-about green tea compound. As one of the most powerful antioxidants known, the health benefits of EGCG include a lower risk of heart attack and stroke, glaucoma, high cholesterol and more. Several studies have also found that EGCG can improve exercise performance, increase fat oxidation, and may help prevent obesity, as it’s known to have a regulatory effect on fat metabolism.

If you drink green tea, you probably assume you’re getting a healthful dose of EGCG with each cup, but new research shows that’s not necessarily the case. An analysis of the strength and purity of more than 20 green tea products by ConsumerLab.com found that EGCG levels in bottled green tea can range from just 4 milligrams (mg) per cup to 47 mg, while brewable green tea (from tea bags, loose tea or a K-cup) contained levels ranging from 25 mg to 86 mg per serving.1

One variety, bottled Diet Snapple Green Tea, reportedly contained almost no EGCG, while Honest Tea Green Tea with Honey contained only about 60 percent of the 190 mg of catechins claimed on the label.2 Added sugars or artificial sweeteners were also common in the bottled tea brands.

This Type of Green Tea Contained the Most Antioxidants

Green tea brewed from loose tea leaves appeared to offer the most potent source of antioxidants like EGCG. One variety, Teavana contained 250 mg of catechins per serving; green tea sold in bags from brands like Lipton and Bigelow contained lower levels, although represented a more cost-effective alternative.

The different tea brands also varied significantly in the amount of caffeine the products contained. While some contained virtually none, others contained 86 mg per serving, which is similar to the amount of caffeine in a regular cup of coffee.

One green tea supplement even contained 130 mg of caffeine in a single capsule, which is more than is found in a cup of coffee! But higher antioxidant levels is only one reason why you may want to choose loose tea over bags…

Some Tea Bags May Leach Hazardous Compounds Into Your Tea

Some tea bags are made with synthetic polymers, such as nylon, thermoplastic, PVC or polypropylene. While these compounds have high melting points, the temperature at which the molecules in polymers begin to break down is always lower than the melting point, which could allow the bags to leach compounds of unknown health hazards into your tea when steeped in boiling water.

Paper tea bags are also potentially problematic, as they are frequently treated with epichlorohydrin, which hydrolyzes to 3-MCPD when contact with water occurs. 3-MCPD is a carcinogen associated with food processing that has also been implicated in infertility and suppressed immune function. I recommend purchasing tea from manufacturers who can certify that their tea bags do not contain epichlorohydrin, and avoid plastic tea bags. Alternatively, you can opt for loose tea instead.

Why Your Green Tea Should Come From Japan, Not China

Green tea plants are known to be especially effective at absorbing lead from the soil, which is then taken up into the plant’s leaves. Areas with excessive industrial pollution, such as China (where nearly 90% of the world’s green tea is produced),3 may therefore contain substantial amounts of lead.4

According to the ConsumerLab.com analysis, tea from brands like Lipton and Bigelow contained up to 2.5 micrograms of lead per serving compared to no measurable amounts in Teavana brand, which gets its tea leaves from Japan.

While the lead in the tea leaves is not thought to leach very effectively into the tea you end up drinking, if you’re consuming Matcha green tea, one of my favorites, it’s especially important that it comes from Japan instead of China. Matcha tea contains the entire ground tea leaf, and can contain over 100 times the EGCG provided from regular brewed green tea.

That said, because you’re consuming the entire leaf, you want to be sure it comes from a non-polluted, high-quality source. The best Matcha green tea comes from Japan and is steamed, rather than roasted or pan-fried. As a result, Matcha green tea retains all the nutrient-rich value possible from the tea leaf, without additives or contaminants.

A Word of Warning About Fluoride in Tea

Both black and green teas are naturally high in fluoride, even if organically grown without pesticides. This is because the plant readily absorbs fluoride thorough its root system, including naturally-occurring fluoride in the soil. According to fluoride expert Jeff Green, there are reports of people who have developed crippling skeletal fluorosis from drinking high amounts of iced tea alone.5

If you live in an area with fluoridated drinking water, as the majority of Americans do, then you could be getting a double dose of fluoride when you drink tea. When selecting tea of any kind, it should preferably be organic (to avoid pesticides) and grown in a pristine environment because, as mentioned, tea is known to accumulate fluoride, heavy metals and other toxins from soil and water, so a clean growing environment is essential to producing a pure, high-quality tea.

What Does the Research Say About Drinking Tea?

Although I still believe pure water should make up the majority of your daily fluid intake, high-quality tea has numerous health benefits to offer, which vary by type. In addition to Matcha tea, I personally enjoy Tulsi tea (aka Holy Basil tea), which is a powerful adaptogenic herb that provides important therapeutic benefits. There is also growing evidence that the polyphenols in tea, including EGCG and many others, may be protective against cancer. Beyond this, the beneficial properties in tea have been known to:

  • Neutralize the effects to your body of harmful fats and oils
  • Inhibit bacteria and viruses
  • Improve digestion
  • Protect against oxidation in your brain and liver
  • Help promote healthy gums

Drinking tea has also been linked to:

Improved mental alertness and slowing of brain-cell degeneration Reduced blood pressure Protection against type 2 diabetes
Lower blood cholesterol and triglyceride levels Lower risk of breast, colon, lung, ovarian and prostate cancers Reduced risk of heart attack and stroke

How to Brew the Perfect Cup of Loose-Leaf Tea

Choosing high-quality tea is extremely important. As the ConsumerLab.com analysis showed, the type of tea you purchase can make all the difference in the amount of beneficial antioxidants it contains, with loose-leaf teas appearing to provide the most. There is an art to brewing tea using loose tea leaves, but once you find your “sweet spot” you may never go back to bagged tea again. Here are a few simple guidelines for making the “perfect” cup of tea:

  • Bring water to a boil in a tea kettle (avoid using a non-stick pot, as this can release harmful chemicals when heated)
  • Preheat your teapot or cup to prevent the water from cooling too quickly when transferred. Simply add a small amount of boiling water to the pot or tea up that you’re going to steep the tea in. Ceramic and porcelain retain heat well. Then cover the pot or cup with a lid. Add a tea cozy if you have one, or drape with a towel. Let stand until warm, then pour out the water
  • Put the tea into an infuser, strainer, or add loose into the tea pot. Steeping without an infuser or strainer will produce a more flavorful tea. Start with one heaped teaspoon per cup of tea, or follow the instructions on the tea package. The robustness of the flavor can be tweaked by using more or less tea
  • Add boiling water. Use the correct amount for the amount of tea you added (i.e. for four teaspoons of tea, add four cups of water). The ideal water temperature varies based on the type of tea being steeped:
    • White or green teas (full leaf): Well below boiling (170-185°F or 76-85°C). Once the water has been brought to a boil, remove from heat and let the water cool for about 30 seconds for white tea and 60 seconds for green tea before pouring it over the leaves
    • Oolongs (full leaf): 185-210°F or 85-98°C
    • Black teas (full leaf) and Pu-erhs: Full rolling boil (212°F or 100°C)
  • Cover the pot with a cozy or towel and let steep. Follow steeping instructions on the package. If there are none, here are some general steeping guidelines. Taste frequently as you want it to be flavorful but not bitter:
    • Oolong teas: 4-7 minutes
    • Black teas: 3-5 minutes
    • Green teas: 2-3 minutes
  • Once the desired flavor has been achieved you need to remove the strainer or infuser. If you're using loose leaves, pour the tea through a strainer into your cup and any leftover into another vessel (cover with a cozy to retain the heat)
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