Green Tea: The Japanese Secret to Weight Loss and Longevity
Quick…what are the three biggest health conditions plaguing Americans today? If you said cancer, heart disease, and obesity, you would likely be right.
Okay, now, what is the one thing that can help reduce your risk for all three? A few hints: it’s natural, you drink it and it’s a subset of the second-most consumed beverage in the world after water.
If you said green tea, you are right.
You’ve probably heard of green tea before, but once you’re done reading this, you’ll never think about green tea the same way again.
And you will likely start drinking it every day to capture some of its remarkable health benefits including its ability to help you lose weight and battle cancer, heart disease and strokes.
Think You Know Green Tea?
Green tea supports your health in so many ways that modern science is still cataloging them. But what exactly is green tea?
Technically, black and green teas are the same, as they both come from the same tea plant, Camellia sinensis. However, the way the tea leaves are treated after harvest determines their fate.
If the leaves are crushed and allowed to naturally ferment (or oxidize), a process that darkens the leaves, then you have black tea.
Conversely, if the leaves are heated, the natural plant enzymes are inactivated. This blocks oxidation, so the leaves hold their green color. And, voila, you have green tea.
But color is far from the only difference. The key difference is the oxidation, or lack thereof.
Oxidation (or Lack Thereof) is the Key
Freshly harvested Camellia sinensis tea leaves contain polyphenols, remarkable compounds with a host of therapeutic benefits. The oxidation that occurs during black tea processing robs the plant of much of its polyphenols and therefore also many of the health benefits they convey.
However, the heating of the leaves blocks the oxidation process, which ironically allows the polyphenols to remain intact. You’d think it would be the other way around, wouldn’t you?
The major polyphenols are primarily flavonoids and include:
- catechins, which are also found in cacao beans (yep, chocolate!)
- proanthocyanidins, which were once referred to as vitamins and are also found in apples, cinnamon, grape seed, and red wine
- epigallocatechin gallate, which is abbreviated and commonly referred to as EGCG
Of these, EGCG is the most widely associated with green tea, and is in fact the nutrient that supposedly gives this common beverage its health advantages. Specifically, proponents of green tea claim it can prevent America’s most feared health conditions: cancer, heart disease, and obesity.
But are these advantages real or just medical lore? Let’s head to the studies to find out.
Green Tea and Cancer Prevention…
Green tea’s ability to prevent cancer is well documented.1 While studies have shown it to be particularly effective in preventing cancers of the gastrointestinal tract (stomach, small intestine, and colon), the areas where it really stands out have been esophageal cancer and breast cancer.
One population-based, case-control study published in the Journal of the National Cancer Institute2 surveyed 902 people with esophageal cancer and 1,552 healthy people, all residents of Shanghai, China. Researchers discovered that drinking green tea reduced the risk for esophageal cancer risk by 57 percent for men and 60 percent for women.
The researchers concluded: “The effects of green tea may be due to polyphenols that possess strong antioxidant properties… suggesting that certain antioxidant micronutrients are protective against cancers of the esophagus and gastric cardia.”
In other words, researchers looked at people with esophageal cancer and compared them to people who don’t have the disease. The researchers then excluded other lifestyle or genetic factors and looked to see if the consumption of green tea had any impact on one group or the other.
They discovered that the polyphenols we described earlier appear to protect against cancers of the esophagus and the upper part of the stomach, which connects to the esophagus.
In the case of breast cancer, a meta-analysis from Carcinogenesis3 looked at four previously published studies on green tea.
They found an approximate 20 percent statistically significant reduction for breast cancer in those people who had a high green tea intake.
While these studies (and the myriad of other research in this area4,5) appear to support the connection between green tea consumption and a reduction in cancer risk, most studies are in laboratory/cell studies, a study that looks at and analyzes other previous studies, or animal studies.
It would be nice to see a few double-blind, randomized, placebo-controlled studies (the “gold standard” in research) on actual humans…not just cells or recaps of other studies. However, given the serious nature of cancer, this may not be feasible.
And, just as there are many studies on green tea’s benefits on a wide variety of cancers, there are also many theories on how green tea helps fight cancer. The key hypotheses include:
- The polyphenols appear to enhance the activity of the body’s antioxidant and detoxifying enzymes.
- Polyphenols prevent the formation of cancer-causing compounds, such as nitrosamines (compounds formed when the nitrites in cured foods bind with amino acids).
- Polyphenols block carcinogen activity by binding to tissue receptor sites. This would be particularly effective in breast cancer prevention. As polyphenols bind to receptor sites on breast tissue, they prevent carcinogens from binding to and harming the cells. In essence, the polyphenols “seal off” the tissue from invasion by carcinogens.
Regardless of how it may work, or how effective it may actually be, the studies and logic behind the mechanism of action is promising enough that sipping a cup or two of hot green tea a day certainly won’t hurt and may actually help prevent some forms of cancer.
Green Tea and Heart Disease…
After cancer, heart disease may be one of the most feared (and common) health conditions. And, proponents of green tea say the toasty beverage can help in this arena as well.
Japanese researchers from Tohoku University School of Medicine spent 11 years studying the relationship between green tea consumption and death from all causes, including cardiovascular disease and cancer.6 The study included 40,530 people ages 40 to 79 who had no history of cardiovascular disease or cancer at the time.
After 11 years of tracking the participants and tabulating everything they ate and drank, as well as their history of disease and current health habits, researchers found that consumption of green tea is associated with reduced mortality due to ALL causes, and green tea specifically produced reduced mortality from cardiovascular disease.
Interestingly, though, green tea consumption was not associated with a reduction in mortality due to cancer. While this appears to negate the studies above, remember that this study looked at reduction in cancer deaths, not prevention of the disease.
When it comes to specific types of heart disease such as high cholesterol or stroke, green tea appears to also have a beneficial effect.
A study of 1,306 males in Japan7 found that those men who drank nine or more cups of green tea a day had an 8 mg/dl reduction in total cholesterol.
This is interesting, but having to drink nine cups a day? That seems a bit unrealistic.
Another study considered more realistic amounts: The study of almost 6,000 non-drinking, non-smoking women age 40 and older found that those who drank five or more cups of green tea per day enjoyed a 50 percent reduction in strokes.8
Again, the studies appear to be promising, but they lack the gold standard double-blind, placebo-controlled protocol we prefer.
Green Tea and Weight Loss…
Green tea’s apparent anti-cancer and heart-protective effects are interesting in their own right, but throw in the theory that green tea also helps you shed excess pounds and burn fat, and nearly all of America should be sitting up and taking notice.
In one randomized, placebo-controlled study,9 researchers randomly divided 10 healthy men into three groups on three separate occasions, giving them green tea extract (50 mg caffeine and 90 mg EGCG), caffeine (50 mg), or a placebo. Each dose was administered at breakfast, lunch, and dinner.
Researchers found that those who took the green tea extract had a statistically significant increase in energy expenditure as compared to the placebo. Those who took the caffeine did not show a significant increase in energy expenditure.
Researchers concluded: “Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content.”
Sounds impressive, but what the heck does it mean? It means that green tea helps rev up your metabolism and burn fat. Now why couldn’t they just say that!?!
Another study,10 this one a meta-analysis, looked at 15 studies—a total of nearly 1,230 participants. Researchers concluded that green tea with caffeine significantly lowered body mass index, body weight and waist circumference when compared to caffeine alone.
Also, when compared to a caffeine-free control, green tea with caffeine was found to be associated with significantly decreased body weight. However, the clinical significance of these reductions was modest at best.
Long story short?
Green tea does appear to help boost your metabolism, but it does just that: “boost.” It will not magically transform you from fat to fabulous overnight.
And if you want to capitalize on this boost, be sure to choose regular green tea—not a decaffeinated version as the decaffeination process eliminates a significant amount of the flavanols and antioxidants—to get the full weight loss effect.
Brew Up for Good Health…
Across the board, the studies on green tea are intriguing, but not completely bulletproof. Still, we believe they are compelling enough to warrant the regular consumption of green tea.
There are several types of green tea, the most common of which come from Japan. Of the many varieties available, the two recommended ones are sencha and matcha.
Sencha comes from green tea whose leaves are exposed to direct sunlight. It is the most common type of green tea in Japan.
Matcha is a fine, almost powdered, green tea made from Tencha tea, which is grown in the shade and has a slightly sweet smell. Matcha is the primary tea used in tea ceremonies.
To reap all of the benefits of green tea, you’ll want to aim for 3-5 8 oz. cups of green tea each day. And to help you get the most out of your tea experience, try these tips:
- For maximum potency, store your green tea leaves or bags in a lightproof, airproof container. And brew a fresh cup every time, allowing the tea to steep for 3-4 minutes.
- Try drinking your green tea “straight up,” just to see how naturally delightful it is. If you prefer a bit of sweetener, try a little honey.
- Tuck a small tin of green tea bags into your purse or briefcase so you’ll always have it handy.
- If you’re eating on the run, look for unsweetened, bottled green tea (such as Ito En). You can even pick up an unsweetened iced green tea at your local Starbucks.
If you prefer not to drink the tea, any of these options provides the same level of protection. You can also opt for 300 to 400 mg daily of green tea extract. Be sure the product is standardized to 80 percent total polyphenol and 55 percent epigallocatechin.
No matter how you pour it, green tea is a cup with clout. With its healthful properties and sensory delights, it’s the one beverage that’s truly worthy of the toast, “To your health!”
1Yang, CS and Wang, ZY. “Tea and cancer.” J Natl Cancer Inst. 1993 July 7;85(13):1038-49.
2Gao, Y et al. “Reduced risk of esophageal cancer associated with green tea consumption.” J Natl Cancer Inst. 1994 June 1;86(11):855-8.
3Sun, CL, et al. “Green tea, black tea as well as breast cancer risk: a meta-analysis of epidemiological studies.” Carcinogenesis. 2006;27(7):1310-15.
4Maryam, R et al. “Green Tea Inhibits Vascular Endothelial Growth Factor (VEGF) Induction in Human Breast Cancer Cells.” J Nutr. 2002;132:2307-11.
5Wu , AH, et al. “Green tea as well as risk of breast cancer in Asian Americans.” Int J Cancer. 2003 Sept. 10;106(4):574-9.
6Kuriyama, S et al. “Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan.” JAMA. 2006 Sept 13; 296:1255-65.
7Kono, S et al. “Green tea consumption and serum lipid profiles: A cross-sectional study in Northern Kyushu, Japan.” Preventive Medicine. 1992 July;21(4)526-31.
8Sato, Y. et al. “Possible contribution of green tea drinking habits to the prevention of stroke.” Tohoku J Exp Med. 1989 April;157(4):337-343.
9Dulloo, AG, et al. “Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.” Am J Clin Nutr. 1999;70(6):1040-5.
10Phung, OJ et al. “Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis.” Am J Clin Nutr. 2010 Jan;91(1):73-81.
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