By Dr. Mercola

When you’re thirsty, pure water is always a good choice, but sometimes you may be craving something different – a cool refreshment on a hot summer day or a warm mug to sip on when temperatures plummet. Green tea fits the bill in both cases and, even better, provides significant benefits to your health.

You’re probably already aware that green tea is healthy… but you may be surprised to learn just how healthy it actually is. Green tea is one beverage you can feel good about enjoying even multiple times a day.

9 Health Benefits of Green Tea

1. Bioactive Compounds with Medicinal Properties

Green tea is rich in naturally occurring plant compounds called polyphenols, which can account for up to 30 percent of the dry leaf weight of green tea.

Within the group of polyphenols are flavonoids, which contain catechins. One of the most powerful catechins is epigallocatechin-3-gallate (EGCG), which has been shown to positively impact a number of illnesses and conditions.

2. Improve Brain Function

Green tea contains theanine, an amino acid that crosses the blood-brain barrier and has psychoactive properties. Theanine increases levels of gamma-aminobutyric acid (GABA), serotonin, dopamine, and alpha wave activity, and may reduce mental and physical stress and produce feelings of relaxation.¹

Theanine may also help to prevent age-related memory decline² and has been shown to affect areas of your brain involved in attention and complex problem-solving.³

3. Increase Fat Burning and Weight Loss

There is some evidence that long-term consumption of green tea catechins is beneficial for burning fat and may work with other chemicals to increase levels of fat oxidation and thermogenesis.

In one recent study, men who took a green tea extract reduced their body fat by 1.63 percent and increased their fat oxidation rates by 25 percent compared to those taking a placebo.⁴ And according to research in Physiology & Behavior:

“Positive effects on body-weight management have been shown using green tea mixtures. Green tea, by containing both tea catechins and caffeine, may act through inhibition of catechol O-methyl-transferase, and inhibition of phosphodiesterase.

Here the mechanisms may also operate synergistically. A green tea-caffeine mixture improves weight maintenance, through thermogenesis, fat oxidation, and sparing fat free mass… 

Taken together, these functional ingredients have the potential to produce significant effects on metabolic targets such as thermogenesis, and fat oxidation.”

4. Lower Your Risk of Cancer

Green tea components have been shown to downregulate the expression of proteins involved in inflammation, cell signalization, cell motility, and angiogenesis, while an association between green tea intake and decreased risk of cancers (including ovarian and breast⁵) have been reported.⁶

Women who drank more than three cups of green tea a day also had a reduced risk of breast cancer recurrence,⁷ and previous research has shown green tea polyphenols act on molecular pathways to shut down the production and spread of tumor cells.⁸

They also discourage the growth of the blood vessels that feed the tumors. EGCG even acts as an antiangiogenic and antitumor agent, and helps modulate tumor cell response to chemotherapy.⁹

5. Lower Your Risk of Alzheimer’s and Parkinson’s

In a study presented at the 2015 International Conference on Alzheimer's and Parkinson's Diseases, those who drank green tea one to six days a week had less mental decline than those who didn’t drink it.¹⁰ In addition, the researchers revealed tea drinkers had a lower risk of dementia than non-tea drinkers.

In another study of 12 healthy volunteers, those who received a beverage containing 27.5 grams of green tea extract showed increased connectivity between the parietal and frontal cortex of the brain compared to those who drank a non-green tea beverage.¹¹

The increased activity was correlated with improved performance on working memory tasks, and the researchers believe the results suggest green tea may be useful for treating cognitive impairments, including dementia.

Green tea polyphenols also appear to have an inhibitory affect on mechanisms involved in triggering Parkinson’s disease, leading researchers to suggest it may be useful for both prevention and treatment.¹²

6. Improve Your Dental Health

Green tea is thought to improve periodontal health by reducing inflammation, preventing bone resorption, and limiting the growth of certain bacteria associated with dental diseases.

Researchers noted that “the more frequently subjects drank green tea, [the] better was their periodontal condition.'¹³ Green tea may even help prevent bad breath.

Researchers concluded, “green tea was very effective in reducing oral malodor temporarily because of its disinfectant and deodorant activities, whereas other foods were not effective.”¹⁴

7. Lower Your Risk of Type 2 Diabetes

Green tea improves lipid and glucose metabolism, prevents sudden increases in blood sugar levels, and has a balancing effect on metabolic rate.¹⁵ One study even found people who consume six or more cups of green tea daily had a 33 percent lower risk of developing type 2 diabetes than those who consumed less than one cup per week.¹⁶

8. Lower Your Risk of Heart Disease and Stroke

Green tea improves both blood flow and the ability of your arteries to relax, with research suggesting a few cups of green tea each day may help prevent heart disease.¹⁷ Study results also show EGCG can be helpful for the prevention of arterio­sclerosis, cerebral thrombus, heart attack, and stroke — in part due to its ability to relax your arteries and improve blood flow.¹⁸

Green tea also appears to inhibit the oxidation of LDL cholesterol in your bloodstream.¹⁹ Oxidized LDL is more harmful than normal non-oxidized LDL because it's smaller and denser. This allows it to penetrate the lining of your arteries, where it will stimulate plaque formation associated with heart disease.

In a meta-analysis of green tea for stroke, meanwhile, it was found that drinking at least three cups of green tea daily lowered stroke risk by 21 percent. The researchers noted, “Drinking tea regularly may be one of the most practical lifestyle changes you can make to significantly reduce your risk of suffering a stroke.”²⁰

9. Increase Longevity

Drinking green tea is associated with reduced mortality due to all causes, as well as reduced mortality due to heart disease. In one study of Japanese women, those who drank five or more cups of green tea daily were 23 percent less likely to due during an 11-year period.

Separate research found elderly individuals (aged 65 to 84) who drank the most green tea were 76 percent less likely to die during the six-year study period.²¹ Research also shows holistic benefits to green tea consumption, including lower blood pressure, oxidative stress, and chronic inflammation.²²

Freshly Brewed Tea Is Best for Your Health

While it may be tempting to purchase pre-made bottled tea, especially the iced variety, be aware that it likely won’t contain the same level of health-boosting flavonoids as freshly brewed tea. Nutrition scientist Dr. Jeffrey Blumberg, director of the Antioxidants Research Laboratory at Tufts University, told Bay Area Bites:²³

“Tea is not stable… You know that cloudy stuff that you see at the bottom of a bottle of ice tea or a gallon batch that you made a few days ago? That’s precipitated flavonoids – and that doesn’t do you any good.”

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.²⁴

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.²⁵ Added sugars or artificial sweeteners were also common in the bottled tea brands. Fortunately, brewing your own tea fresh at home is easy. 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. (This step is unnecessary if you’ll be drinking your tea iced).
• 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 to 185°F or 76 to 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 to 210°F or 85 to 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 to 7 minutes
  • Black teas: 3 to 5 minutes
  • Green teas: 2 to 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)
• If you prefer iced tea, transfer your tea to the refrigerator to cool or add just enough ice to bring the temperature down (be careful not to water it down too much).

Tips for Getting the Most Health Benefits Out of Your Tea

There are many variables that affect just how healthy your cup of green tea is. A telltale sign of high-quality green tea is that the tea is in fact green. If your green tea looks brown rather than green, it’s likely been oxidized, which can damage or destroy many of its most valuable compounds. Many enjoy using loose tea leaves, which ConsumerLab found may offer even more antioxidants (while also avoiding potential toxins in tea bags). Other considerations include:

1. Add Lemon:To boost the benefits of green tea, add a squirt of lemon juice to your cup. Previous research has demonstrated that vitamin C significantly increases the amount of catechins available for your body to absorb. In fact, citrus juice increased available catechin levels by more than five times, causing 80 percent of tea's catechins to remain bioavailable.²⁶
2. Skip the Milk: The proteins in milk may bind to and neutralize the antioxidants in tea, such that its health benefits are significantly reduced. One study even found “All [beneficial vascular protective] effects were completely inhibited by the addition of milk to tea.”²⁷
3. Choose Organic and Grown in a Non-Polluted Environment: Green tea plants are known to be especially effective at absorbing lead from the soil, which is then taken up into the plants’ leaves. Areas with excessive industrial pollution, such as China (where nearly 90% of the world’s green tea is produced),²⁸ may therefore contain substantial amounts of lead.²⁹ Both black and green teas are naturally high in fluoride as well, 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. There are reports of people who have developed crippling skeletal fluorosis from drinking high amounts of iced tea alone.³⁰
   
   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. A clean growing environment is essential to producing a pure, high-quality tea, and, ideally, the water you use to brew it should be fluoride-free as well.