Nadine Taylor, M.S., R.D.
Green Tea Info
Everything you ever wanted to know about green tea, and more!
These articles explain it all, and new ones appear every month
at the bottom of the page. Keep coming back!
Article 1
A Steaming Cup of Medicine
You have to imagine it –a steaming, fragrant cup of green tea. The clear, pale green liquid gives off a delicious aroma somewhat like wet hay mixed with the scent of apples or pears. You lift the cup to your lips and take the first sip. The comforting liquid rolls over your tongue and eases down your throat, brightening and warming as it goes. Its slight astringency freshens your mouth, making it feel naturally clean. This warm, delightful beverage is soothing, especially if you take a moment to sit and sip it slowly. But at the same time, it’s also stimulating, giving you a much needed pick-me-up in the morning or the middle of the long afternoon. Is it any wonder that tea has been enjoyed for nearly 5,000 years – and that it’s the world’s most widely consumed beverage, next to water?
Yet green tea is a lot more than just a delicious and satisfying drink -- it also has medicinal properties that are nothing short of amazing. Way back in the year 1211 the Japanese monk Eisai wrote that "Tea is a miraculous medicine for the maintenance of health. Tea has an extraordinary power to prolong life." And today, scientific are confirming that what Eisai said may be true, finding that green tea can boost the immune system, inhibit the cancer process at virtually every stage, regulate cholesterol levels, assist in weight loss, fight free radical damage, and ward off viruses, fungi and food-borne bacteria. It also helps inhibit dental plaque formation, lower the risk of type 2 diabetes, slow cognitive decline, and may even help increase the lifespan. Virtually no other substance on earth can claim such a wide range of health benefits!
I’m Nadine Taylor, a Registered Dietitian with a great interest in the healing power of foods. I have been so impressed by the science behind green tea’s health benefits that I started collecting green tea studies and information about ten years ago and eventually wrote a book about it. My aim in this column is to bring that knowledge to you, explaining how green performs its health-promoting "miracles," telling about the fascinating history and customs of tea drinking, and revealing some interesting new tea tidbits. (Did you know that green tea extract can grow hair?) My articles and question-and-answer column will appear monthly, and I hope you’ll join me. And don’t forget to bring along a nice hot cup of green tea!
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Article 2
What Is Green Tea, Anyway?
Green, black, oolong, herbal – what’s the difference? Well, first of all the word "tea" is correctly used only when it refers to leaves taken from the Camellia sinensis bush. And that means that herbal teas really aren’t tea – only green, black and oolong tea are the "real thing." That said, the way the Camellia sinensis leaves are processed will determine which of these three choices the end product becomes.
To make black tea, the freshly picked tea leaves must be fermented. Fermenting occurs when an enzyme in the tea leaf called polyphenol oxidase combines with oxygen, so the leaves are left in the sun to wither and dry for 18-24 hours, then broken up to encourage further fermentation.. Then firing the leaves stops the fermentation and dries them. Making oolong tea is similar, although the withering and fermenting processes are shorter, resulting in a partially-fermented leaf. But to make green tea the leaf isn’t fermented at all – in fact, just the opposite! The tea leaves are steamed almost immediately after picking in order to stop the fermentation process, after which they are rolled and dried.
The health benefits of the resulting tea will largely be determined by whether or not the tea leaf has been fermented. The fresh tea leaf contains large amounts of catechins (pronounced "CAT-i-kins"), powerful disease fighters and potent antioxidants that give green tea its health-enhancing abilities. But when exposed to air and polyphenol oxidase, the catechins change into completely different compounds called theaflavins and thearubigens. The theaflavins and thearubigens, which give black tea its distinctive taste, aroma and dark color, do have some health benefits, but not the same wide-ranging antioxidant and disease-fighting prowess seen in the catechins.
So in green tea manufacturing, it’s extremely important to rush the freshly picked leaves from the field to the manufacturing plant, being careful not to break or bruise them. There, the leaves are steamed or pan-fired immediately to inactivate the polyphenol oxidase. Afterwards, it’s safe to roll, twist, dry and package the leaves without worrying about obliterating the catechins. Yet even after the manufacturing process has been completed, green tea catechins can be destroyed if exposed to oxygen for too long. That’s why you should always keep your green tea in an air-tight container, even if it’s already in tea bag form. Remember: oxygen is the catechins’ worst enemy.
Article 3
The Power of the Catechins
For thousands of years the Chinese have known that drinking tea is good for your physical and mental health. But almost nobody in the Western world thought twice about the tea/health connection until the 1970’s. That’s when researchers first noticed a much lower rate of cancer deaths among people living in Japan’s Shizuoka Prefecture compared to people living in other areas of Japan.
When they looked at the lifestyle and habits of the two groups, the researchers could only find one major difference:those living in the Shizuoka Prefecture drank a lot more green tea. The reason they were such big tea drinkers? The Shizuoka Prefecture is Japan’s premier tea-growing region and, with acres of tea springing up practically right outside everybody’s door, those who lived there sipped green tea almost continually throughout the day. Many even refreshed the teapot every so often with a few fresh tea leaves plucked from a nearby bush.
But what was it about green tea that seemed to be protective against cancer? After much study, the researchers came up with the answer: the catechins.
The catechins (pronounced CAT-i-kins) are naturally-occurring plant chemicals found primarily in green tea leaves that have powerful antioxidant and disease-fighting properties. You can find some catechins in a few other foods (such as black tea, ginkgo biloba leaves, dark chocolate and wine), but green tea contains the lion’s share.
There are five types of catechins, with hard-to-pronounce names like gallocatechin, epicatechin, and epigallocatechin. The one that has the most potent health benefits is epigallocatechin gallate, or EGCg for short. The catechins are part of a larger group called the flavonoids which, in turn, are part of an even larger group called the polyphenols. That’s why you’ll sometimes hear the catechins referred to as "tea flavonoids" or "tea polyphenols."
Since scientists first isolated these substances in the 1970’s, the catechins (especially EGCg) have been the subject of thousands of scientific studies. They are best known for their powerful antioxidant action, which reduces the free radical damage that is linked to cancer, cardiovascular disease and other degenerative diseases.
But the catechins can also work other "wonders." To name a few: they can destroy certain powerful bacteria (including salmonella and cholera), inhibit the action of viruses (such as flu virus and HIV), assist in weight loss, fight tooth decay and stimulate the immune system. Clearly the catechins are potent health-protectors! And they are only found in significant quantities in green tea.
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Article 4
How Much Green Tea Do You Need?
By now you know that green tea catechins can do great things for your health. But how much green tea do you need on a daily basis to experience the health benefits? Most studies have concluded that the "magic number" lies somewhere between 300 -1,000 mg. of catechins per day, or the equivalent of 3-10 cups of green tea. This recommendation is based on the idea that the average cup of green tea contains 100 mg. of catechins per cup. However, studies have shown that some cups of green tea contain only half that amount or even less.
The variation in catechin content is probably due to the fact that green tea leaves are a crop like any other. They can be young or old, fresh or stale, from rich or poor soil. And during harvesting, processing and packaging, the tea leaves can be exposed to different conditions that either preserve or destroy their nutrients. The way you handle, brew and store your green tea at home can also make a difference in the catechin content.
· Use purified water, as the chlorine in tap water degrades the catechins and destroys the subtle flavor of green tea.
· Avoid tea kettles made of metal alloys containing iron since iron lowers the antioxidant of activity of catechins.1 Kettles made of high-grade stainless steel, nickel-plated metal alloys, copper,polypropylene plastic, lead-free porcelain or glass are best.
· Bring the water to a full boil and add to the tea immediately. Steeping tea leaves at 212° F for five minutes releases approximately 80 percent of the catechins. In contrast, the catechin release is over one-third less when tea is steeped at 176° F.2
· Don’t put the tea leaves in water and then microwave them. This will "overcook" them and destroy some of the catechins.
· Keep your tea in an airtight container in the refrigerator, even if it comes in pre-packaged bags. This will keep the tea leaves fresher and help preserve the catechins.
Although it may sound a little complicated, making a health-enhancing, delicious cup of tea is really easy. As Senno Rikyu, the Greatest of all Tea Masters, said back in the 16th century: "Tea is nothing other than this: Heat the water, prepare the tea and drink it with propriety. That is all you need to know."
Footnotes:
1 Kumamoto M, Sonda T, Nagayama K, Tabata M. Effects of pH and metal ions on antioxidative activities of catechins. Biosci Biotechnol Biochem 2001:65:126-32.
2 Khokhar S, Magnusdottir SG. Total phenol, catechin, and caffeine contents of teas commonly consumed in the United Kingdom. J Agric Food Chem 2002; 50(3):565-70.
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Article 5
What in the World is an Antioxidant?
Okay, so by now you’ve undoubtedly heard about green tea’s wonderful antioxidant abilities, and how this particular quality helps it fight dangerous diseases like cancer and heart disease. But what is an antioxidant, anyway? And why would anything that’s anti-oxygen be good for you?
Despite their name, antioxidants don’t work against oxygen. They work against a chemical reaction called oxidation, the same process that turns bananas black, rusts metal and makes oil rancid. Oxidation is the interaction between oxygen molecules and the substances they come in contact with. When that substance happens to be living tissue, damage and disease can occur.
Oxidative damage, the harm caused by oxidation, is primarily caused by free radicals, highly reactive, unstable molecules that travel around the body wreaking havoc. Although free radicals can be generated by exposure to UV rays, toxins, cigarette smoke, microbes and other sources, the most common source is the oxygen molecule itself.
Oxygen typically travels throughout the body in pairs, and these two molecules share electrons. But sometimes this double molecule splits into two separate oxygen molecules called singlet oxygen. When this happens, there are no longer enough electrons to go around, so each oxygen molecule ends up one electron short. This destabilizes the molecule, in a sense throwing it off balance. In order too stabilize itself, it races off throughout the body in search of another electron.
But singlet oxygen doesn’t just wait for a spare electron to float on by. Instead, it boldly steals one from some other molecule. This destabilizes the "new" molecule which, in turn, careens off to steal an electron from yet another molecule. The process ofserial "electron stealing" damages cells, tissues, organs and even entire body systems, and is believed to be a major cause of cancer, heart disease, aging and many other conditions.
Antioxidants work against "electron stealing" by neutralizing and stabilizing free radicals. They do this by donating an electron so that singlet oxygen and other free radicals no longer have the urge to "steal." And while the body does produce a certain amount of antioxidants for the express purpose of taking care of such problems, it also needs the added help of antioxidants found in foods. Among others, these include beta-carotene, vitamins C and E, the mineral selenium, and various phytochemicals such as lycopene and quercetin. But the catechins, especially EGCg, are among the most powerful and effective antioxidants of all.
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Article 6
Green Tea & Obesity
Green tea has become the latest weapon in the war on weight. Oprah is a recent enthusiast, vowing that she’d trade her coffee for green tea when Dr. Nicholas Perricone told her she could lose weight simply by making this substitution. But does it really work? The results of some new studies are promising, indicating that green tea can increase the rate of calorie burning, prevent excess weight gain and even reverse established obesity. And although most tests have been performed on laboratory animals, at least one with humans showed that taking in the equivalent of 3 cups of green tea per day helped the body burn a significant amount of additional calories.
Increased rate of fat burning - A 1999 study published in the American Journal of Clinical Nutrition looked at the effects of green tea extract on energy "burning" in humans.1 Men who took daily doses of a green tea extract containing EGCg plus caffeine, in an amount equivalent to that found in about 3 cups of green tea, burned about 80 more calories per day than those who didn’t take the extract. (Taking the caffeine without the EGCg didn’t have the same effect.) While burning an extra 80 calories per day may not seem like much, over the course of a year that adds up to 29,200 calories, or a little more than 8 pounds lost – without making any other changes!
Prevention of excess weight gain - In a study involving animals, green tea extract helped prevent obesity. Two groups of mice were placed on a high-fat diet designed to ensure they would gain weight, with only one group also receiving green tea extract. The mice that were given green tea extract ended up gaining 47% less weight than those that didn’t get the extract.2
Reversal of obesity - In a 2005 study published in the Annals of Nutrition and Metabolism, green tea extract actually helped to reverse established obesity. Rats were deliberately overfed to make them obese. But when the obese rats were given supplemental EGCg, the amount of fatty tissue on their bodies decreased markedly, reversing their obesity.3
What happens in the body to produce such fat-fighting results? Green tea’s EGCg is believed to rev up the fat-burning effects of brown fat,4 a special kind of body fat that burns calories at a very high rate. In animal studies, green tea has been found to help send glucose to muscle tissue where the glucose is more likely to be burned, rather than to fat tissue, where it’s more likely to be stored.5 And in test-tube studies, green tea extract inhibited the action of fat-digesting enzymes,6 meaning the fat from foods may be less likely to be broken down and absorbed in the digestive tract.
More research is needed before we can say that green tea definitely helps you lose weight, but it certainly looks like a good bet!
Footnotes:
1) Dulloo AG, Duret C, Rohrer D, 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):1040-50.
2) Shimotoyodome A, Haramizu S, Inaba M, et al. Exercise and green tea extract stimulate fat oxidation and prevent obesity in mice. Med Sci Sports Exerc 2005;37(11):1884-92.
3) Wolfram S, Raederstorff D, Wang Y, et al. TEAVIGO (epigallocatechin gallate) supplementation prevents obesity in rodents by reducing adipose tissue mass. Ann Nutr Metab 2005;49(1):54-63. Epub 2005 Feb 25.
4) Choo JJ. Green tea reduces body fat accretion caused by high-fat diet in rats through beta-adrenoceptor activation of thermogenesis in brown adipose tissue. J Nutr Biochem 2003;14(11):671-76.
5) Murase T, Harmizu S, Shimotoyodome A, et al. Green tea extract improves running endurance in mice by stimulating lipid utilization during exercise. Am J Physiol Regul Integr Comp Physiol 2006;290(6):R1550-56.
6) Juhel C, Armand M, Pafumi Y et al. Green tea extract (AR25) inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro. J Nutr Biochem 2000;11(1):45-51
Article 7
How Green Tea Fights Cancer
Cancer is the uncontrolled growth of body cells. As teh cells multiply and grow wildly, they "forget" how they're supposed to act and begin to take on dangerous new roles. Like selfish bullies, cancer cells gobble up nearby territory and resources, damaging and destroying healthy tissue. The cancer process unfolds in three stages: initiation, promotion and progression. And both test-tube and animal studies have shown that green tea can fight cancer at all three.
Fighting cancer before it starts
During the initiation stage, a healthy cell is exposed to free radicals and other cancer-causing substances which break into the cell, "hijack" its DNA, and change that cell into a cancer cell. You can think of the cell as a computer that someone has hacked into and reprogrammed. Green tea's catechins can help prevent or minimize this "reprogramming by stabilizing free radicals and making certain carcinogens less toxic. The catechins may also help to prevent cancer-causing substances from binding to the DNA of healthy cells in the first place.
Keeping cancer from "getting into gear"
After a cell is initiated by cancer-causing substances, it might lie quietly for weeks, months, or even years, causing no real damage. But during the promotion stage, something "trips a switch" and the initiated cell starts to multiply uncontrollably, forming a mass of tissue called a tumor. It's as if someone has just logged on to that newly "reprogrammed computer," the initiated cell. Studies have found that green tea catechins can inhibit or even prevent this "promotion" step.
The catechins can also fight cancer at the next step in the cancer process. If the promotion stage is successful and a tumor does begin to grow, it will need a blood supply in order to feed itself. It establishes a blood supply by creating its own blood vessels and plugging them into those found in nearby healthy tissue, a process called angiogenesis. The catechins help to slow or even call a halt to angiogenesis, effectively starving the tumor.
Slowing the growth and spread of tumors
During the progression stage, the tumor invades healthy tissue, eats up nutrients and crowds out healthy cells. Left to its own devices, the tumor can cause massive tissue damage and, in certain cases, death. Green tea's catechins help ward off cancer at the progression stage by slowing tumor growth. The "super-catechin" EGCg also encourages cancer cells to "self-destruct."
In light of these many anti-cancer effects, it's not suprising that several studies of large groups of people have shown that drinking green tea can help protect against various cancers including those of the breast, lung, prostate, skin and stomach. While more study is needed before we can say for sure that green tea actually prevents cancer in humans, the prospects look very promising.
Article 8
Green Tea and Breast Cancer
Scientists have long been curious about the fact that breast cancer rates are lower in countries where green tea consumption is high. Can drinking green tea really keep breast cancer at bay? Although conflicting evidence exists, several studies indicate that this delightful beverage may indeed be able to help.
Animal studies have shown that green tea or green tea extract delays the appearance of breast tumors, strengthens the cancer-fighting effects of the breast cancer drug tamoxifen, and not only reduces tumor size, but encourages breast cancer cells to "commit suicide" while leaving healthy cells alone. But test tubes and animals aren't the same as humans. Can green tea do anything about breast cancer in women?
Only a few studies exixt, but their results are exciting. In a 2003 study of Asian American women living in Los Angeles, published in the International Journal of Cancer, the health and habits of 501 women with breast cancer were compared to those of 594 women who did not have the disease.¹ The researchers found that those who drank more than 3 oz. of green tea per day had a 47% lower risk of developing breast cancer than those who drank no green tea at all. And those who drank at least some green tea (but less than 3 oz. per day) had a 29% lower risk. Pretty impressive results for less than ½ cup of green tea per day!
In a similar study published in the May, 2007 issue of Carcinogenesis, 1,009 women in Southeast China with breast cancer were compared to 1,009 age-matched healthy women. The researchers collected information on each woman's diet, lifestyle and green tea consumption. They found that those who drank an average of 1/2 to 2/3 cup of green tea per day for a year had a reduction in breast cancer risk of 41%. And even those who drank very small amounts of green tea (less than 1 1/2 cups per week for a year) decreased their breast cancer risk by 13%. 2
Clearly, more studies of the green tea/breast cancer link are needed. But since green tea is nontoxic, inezpensive, and readily available (not to mention quite tasty!), it couldn't hurt to sip a few cups every day - and possibly reap big health rewards down the line.
Footnotes:
1 Wu AH, Yu MC, Tseng CC, et al. Green tea and risk of breast cancer in Asian Americans. International Journal of Cancer 2003;106(4):574-9.
2 Zhang M, Holman CD, Huang JP, Xie X. Green tea and the prevention of breast cancer: a case-control study in southeast China. Carcinogenesis 2007;28(5):1074-78.
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Article 9
Green Tea and Prostate Cancer
Each year in the U.S. more than 220,000 men receive the unwelcome news that they've developed prostate cancer and, unfortunately, 31,000 men die of the disease. Yet in Asian countries, the rates of prostate cancer are surprisingly low. How did the Asians get to be so lucky? Many researchers think it may have to do with their tea consumption.
At least two studies of large populations have shown that men who regularly consume tea (black or green) have a lower incidence of prostate cancer.1,2 And as the frequency, duration and quantity of green tea consumption goes up, the risk of developing prostate cancer goes down.3 This was dramatically illustrated in a study of men with pre-cancerous prostate lesions, which made them particularly likely to develop prostate cancer. Those who received daily doses of green tea catechins were found to be 90 percent less likely to develop full-blown prostate cancer than those who didn't receive catechins.4
Why would green tea have an effect on prostate cancer? Well, for starters, once green tea is ingested, its catechins make their way through the bloodstream and settle right there inside the prostate tissue. From this fortunate position, the catechins appear to fight prostate cancer by:
Slowing the growth and speeding the death of cancer cells
In "test tube" studies, green tea's EGCg not only slowed the growth of human prostate cancer cells but promoted cancer cell “suicide.”5
Stopping cancer before it starts
Animal studies have shown that green tea catechins reduce the activity of an enzyme called ornithine decarboxylase (ODC), which is believed to play a part in the start-up of prostate cancer.
Inhibiting COX-2
The enzyme COX-2, which is found in large quantities in prostate cancer tissue, appears to play a role in the cancer process. Studies have shown that medications that inhibit COX-2, like the arthritis drug celecoxib, slow prostate cancer growth in animals. Green tea's EGCg has also been found to inhibit COX-2 in prostate cancer cells7 indicating that it, too, may be helpful in combating the disease.
But an even better idea may be combining EGCg with celecoxib to deliver a double whammy to prostate cancer. In mice bred to develop the disease, prostate tumor growth was slowed 42 percent by EGCg and 57 percent by celecoxib. But when the two were combined, the growth of prostate tumors was slowed by an astounding 81 percent! 8
This finding is especially important since taking too much celecoxib carries with it an increased risk of heart attacks. But when combined with green tea's EGCg, lower doses of the medication may be even more effective than the higher “stand-alone” doses.
Footnotes:
1) Heilbrun LK, Nomura A, Stemmermann GN. Black tea consumption and cancer risk: a prospective study. British Journal of Cancer 1986;54:677-83.
2) Jain MG, Hislop GT, Howe GR, et al. Alcohol and other beverage use and prostate cancer risk among Canadian Men. International Journal of Cancer 1998;78(6):707-11.
3) Jian L, Xie LLP, Lee AH, Binns CW. Protective effect of green tea against prostate cancer: a case-control study in southeast China. International Journal of Cancer 2004;108(1):130-35.
4) Bettuzzi S, Brausi M, Rizzi F, et al. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study. Cancer Research 2006;66(2):1234-40.
5) Gupta S, Ahmad N, Nieminen AL, Mukhtar H. Growth inhibition, cell-cycle dysregulation, and induction of apoptosis by green tea constituent (-)-epigallocatechin-3-gallate in androgen-sensitive and androgen-insensitive human prostate carcinoma cells. Toxicology & Applied Pharmacology 2000;164(1):82-90.
6) Gupta S, Ahmad N, Mohan RR, et al. Prostate cancer chemoprevention by green tea: in vitro and in vivo inhibition of testosterone-mediated induction of ornithine decarboxylase. Cancer Research 1999;59(9):2115-20
7) Hussain T, Gupta S, Adhami VM, Mukhtar H. Green tea constituent epigallocatechin-3-gallate selectively inhibits COX-2 without affecting COX-1 expression in human prostate carcinoma cells. International Journal of Cancer 2005;113(4):660-69
8) Adhami VM, Malik A, Zaman N, et al. Combined inhibitory effects of green tea polyphenols and selective cyclooxygenase-2 inhibitors on the growth of human prostate cancer cells both in vitro and in vivo. Clinical Cancer Research 2007;13:1611-19.
Green Tea and Cholesterol
These days it seems like just about everybody is worried about cholesterol levels. But cholesterol is actually a good thing. This fatty, waxy substance is absolutely vital to life as it’s used to build cell membranes, insulate nerve fibers and create hormones.
The problems begin when there is a buildup of certain kinds of cholesterol – specifically, total cholesterol and LDL - and too little of a third kind, HDL. Too much of the former can result in clogged arteries that can lead to a heart attack or stroke. And too little of the latter can cause similar results, since HDL carries excess cholesterol out of the body. Luckily, drinking green tea seems to nudge all three kinds of cholesterol in the right direction. Studies of large populations have found that, on average, the more green tea that people drink the lower their total and LDL cholesterol levels. The best results are seen with about 10 daily cups of green tea, but you don’t have to drink nearly that much to make a difference. In one human study, just 2 cups of green tea per day lowered LDL cholesterol levels by as much as 13 mg.1 And while a low fat diet may be the first thing your doctor recommends to control cholesterol, green tea has been found to help keep cholesterol levels down even when the diet is high in fat. Studies of animals fed a diet rich in lard and cholesterol found that those that received green tea catechins had lower cholesterol levels and other indicators of heart disease risk than those that didn't receive the catechins. 2 Researchers believe that green tea lowers blood cholesterol by reducing its absorption in the digestive tract while increasing its rate of excretion. But perhaps even more important than either of these is green tea’s ability to fight the conversion of LDL to its more dangerous, oxidized form. When LDL is oxidized, it gets sticky and tends to cling to the walls of your arteries. Oxidized LDL is a major factor in the development of atherosclerosis (the buildup of plaque in the arteries), and greatly increases your risk of suffering a heart attack or stroke. But green tea, through its antioxidant action, does much to protect LDL from oxidation. The result? Your body may produce less of this sticky, clinging form of cholesterol so your arteries stay cleaner and less likely to clog.
Footnotes:
1Erba D, Riso P, Bordoni A, et al. Effectiveness of moderate green tea consumption on antioxidative status and plasma lipid profile in humans. J Nutr Biochem 2005;16(3):144-149.
2Muramatsu K, Fukuyo M, Hara Y. Effect of green tea catechins on plasma cholesterol level in cholesterol-fed rats. J Nutr Sci Vitaminol (Tokyo) 1986;32(6):613-622.
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Article 11
Green Tea and Cardiovascular Disease
Cardiovascular disease (CVD) is a “catch-all” term for a group of diseases of the heart and blood vessels that that can lead to a heart attack, stroke or heart failure. High blood pressure, coronary heart disease, cerebrovascular disease and other conditions are all forms of CVD. It's terrifying to think that your heart, that all-important pump, or your brain, that vital control center, could suddenly stop working. Unfortunately, it happens to thousands of Americans every day. Green tea is heart-healthy! Luckily, it appears that green tea can offer the heart some protection. Studies of large populations have linked green tea to a wide range of cardiovascular benefits, including:
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decreased coronary artery disease
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lower total cholesterol
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lower levels of LDL “bad” cholesterol
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higher levels of HDL “good cholesterol”
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decreased levels of blood fats (triglycerides) following a fatty meal
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a reduced risk of developing high blood pressure
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a 50% decrease in the rate of stroke and brain hemorrhage (in those drinking 5 cups of green tea/day)
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a 31% reduction in the risk of dying of CVD (in women drinking 5 cups of green tea/day)
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a 16% reduction in the risk of dying from all causes (in men or women drinking 5 cups of green tea/day)
How does green tea do all of this?
Theories abound, but of great importance is green tea’s role in reducing the oxidation of LDL, the “bad” cholesterol. When LDL is oxidized, it becomes sticky and more likely to cling to artery walls, forming plaque. It also irritates artery walls, producing wounds that provide a good base for plaque buildup. By reducing the oxidation of LDL, green tea may not only protect artery walls from damage, but also lessen the formation and buildup of artery-clogging plaque.
And that’s not all. Epidemiological studies have shown that green tea can help fight obesity and protect against type 2 diabetes, two major risk factors for CVD. And animal studies suggest that green tea can lower blood pressure, while lab studies show that green tea’ EGCg decreases the clumping of blood platelets that can form deadly clots.
CVD is everybody's problem
This year alone an estimated 1.2 million of us will have a new or recurrent heart attack, and about 700,000 of us will suffer a new or recurrent stroke. And of all of the things we do to protect ourselves, developing a daily habit of drinking green tea may prove to be one of the best.
Article 12
Green Tea vs. the FDA: Who's Right?
In June 2005, a green tea company called Ito En Ltd. asked the FDA for permission to put a claim on their labels that said drinking 5 ounces of green tea daily might reduce the risk of cardiovascular disease (CVD). To back up their claim, they submitted 105 studies, articles and other publications. Nearly a year later the FDA said no, insisting that, “There is no credible evidence to support qualified health claims for green tea or green tea extract and a reduction of a number of risk factors associated with CVD.”
Yet over the past 25 years, countless studies showing the positive effects of green tea on several important risk factors for cardiovascular disease have been published in scientific journals. So was the FDA wrong? Or was the green tea claim untrue? The answer is a resounding “neither.” The fault lay on both sides. Here’s why:
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The petitioner’s claim was irresponsible
Ito En Ltd. wanted permission to say that drinking just 5 ounces of green tea daily could reduce several risk factors for cardiovascular disease. Yet most studies have shown that green tea reduces certain CVD risk factors with a daily intake of 4-5 cups, 1,2 and improves cholesterol at about 10 daily cups.3 One-half cup daily? That's a hard case to prove.
The FDA used an antiquated definition of CVD risk factors
The case got even harder to prove when the FDA narrowed the definition of a cardiovascular disease risk factor to high total cholesterol, high LDL cholesterol or high blood pressure. That meant that all studies showing that green tea helps fight oxidized LDL, obesity, stress, low HDL, diabetes or platelet stickiness simply didn’t count.
Many studies were ignored
The only studies the FDA deemed worthy of consideration were human studies – all animal and “test tube” studies were ignored. And not all kinds of human studies were included – review studies and meta analyses were considered background information only.
The evidence was winnowed down
Because of all of these restrictions, the FDA managed to reduce the 105 submitted studies, articles and papers to a grand total of only 11! And it was on the basis of these 11 studies that the FDA concluded that there was “no credible evidence to support qualified health claims” for green tea and a reduction in CVD risk.
Was the FDA wrong?
According to their current standards, no. However, the FDA desperately needs to acknowledge such well-documented and universally accepted CVD risk factors as increased LDL oxidation, excess body weight, low HDL, diabetes and increased platelet “stickiness” – all of which are positively influenced by green tea.
It would also help if future petitioners would consider recommending up to 10 cups of green tea per day (or the equivalent in green tea extract) instead of the ridiculously small amount of 5 ounces.
And, last but notleast, we need researchers to conduct more human studies on green tea’s effects on CVD. Then maybe next time we’ll have the ammunition we need to get the FDA’s much-wanted stamp of approval.
Footnotes:
1) Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer and all causes in Japan: the Ohsaki study. JAMA 2006;296(10):1255-65.
2) Sasazuki S, Kodama H, Yoshimasu K, et al. Relation between green tea consumption and the severity of coronary atherosclerosis among Japanese men and women. Ann Epidemiol 2000;10(6):401-8.
3) Tokunaga S, White IR, Frost C, et al. Green tea consumption and serum lipids and lipoproteins in a population of healthy workers in Japan. Ann of Epidemiol 2002;12(3):157-65.
Article 13
Green Tea and Caffeine
Ever since 8th century Buddhist monks discovered that it could help them stay awake during marathon meditation sessions, tea has been used to increase energy, brighten the mood and refresh the mind. The invigorating effects of tea are due to caffeine, a central nervous system stimulant that fights sleepiness, speeds up the heart rate, increases alertness, improves athletic endurance, assists in weight loss and may even heighten intellectual activity.
Of course, the downside of caffeine is that too much can make you nervous, irritable, and unable to fall asleep at night. It can also reduce fine motor coordination and trigger headaches and dizziness. Most healthy adults can handle 200-250 mg. per day without adverse effects, but some find that even a small dose makes them jittery.The best of both worlds
When it comes to caffeine, green tea may offer the best of both worlds -- just enough to brighten the mood, but not enough to trigger sleepless nights. The average cup of green tea contains about 20 mg of caffeine, while black tea has about 40 mg, and drip coffee packs a nerve-jangling punch of 90-150 mg. Although some who are sensitive to caffeine may find that drinking green tea (especially in large amounts) keeps them awake at night, most people don't have this problem. That may be because green tea also contains theanine, an amino acid that functions as a natural tranquilizer.Decaffeinated tea
For those who are really serious about limiting their caffeine, there is always the option of drinking decaffeinated tea. But beware, as the standard way of decaffeinating tea (using ethyl acetate) obliterates about 70 percent of green tea’s catechins. This method involves soaking the tea leaves in a chemical solvent called ethyl acetate, which binds to the caffeine. Then both the ethyl acetate and the caffeine are boiled away. Unfortunately, most of the health-promoting catechins also disappear in the process.
The carbon dioxide method (also referred to as "effervescence") is a much gentler, more natural process. The tea leaves are soaked in liquefied carbon dioxide gas, which binds to the caffeine and "soaks it out" of the leaves. The liquid and the caffeine are then poured off (no heating required), leaving about 95 percent of the tea catechins intact.
So if you do decide to drink decaffeinated green tea, be sure to look for a brand that uses the carbon dioxide or effervescence method. Otherwise, you may be drinking a brew that’s essentially devoid of catechins.
Article 14
Drink Away Your Stress
Drinking a nice hot cup of green tea can almost always make you feel better. But did you know that certain natural components of green tea have a direct effect on the body, increasing relaxation, easing depression and otherwise improving the mood? A growing body of evidence indicates that both green tea catechins and theanine, an amino acid found in green tea, can bring about positive changes to both body and mind.
Animal studies have found that the catechins increase insulin sensitivity, which means they help insulin do a better job of delivering glucose to the cells, including the cells of the brain. This is important because the brain runs on glucose, and when glucose levels fall too low, you can become depressed, fatigued, irritable and just plain moody. (Just think about how your mood disintegrates when you get overly hungry!)
But perhaps the most important mood enhancer found in green tea is theanine, the amino acid that gives the tea its mellow taste. Theanine has been shown to reduce mental and physical stress and promote feelings of relaxation. One human study found a significant increase in alpha-brain wave activity (that "relaxed yet alert" state cultivated in yoga class) after volunteers took 200 mg of theanine dissolved in water.1 In another human study, theanine decreased two of the body’s responses to stress – heart rate and salivary immunoglobulin A.2 And in animals given an intravenous dose of theanine following a dose of caffeine, the theanine calmed the "jittery" effects of the caffeine.3 No wonder you don’t get the same "buzz" from green tea that you do from other caffeine-containing drinks!
Tests performed on animals give two clues as to how theanine affects the brain and helps improve the mood. First, it significantly increases the brain’s levels of dopamine and serotonin, neurotransmitters that are linked to a sense of well-being. And second, theanine releases GABA (gamma amino butyric acid) in the brain, which calms brain over-excitation, eases anxiety and promotes relaxation.
Theanine works best at doses of 50-200 mg, with effects typically being felt within 30 minutes of ingestion and lasting for 8-10 hours. Coincidentally, there’s about 50 mg. of theanine in one cup of green tea. So have a cup and relax!
Footnotes:
1) Ito K, Nagato Y, Aoi N, et al. Effects of L-theanine on the release of alpha-brain waves in human volunteers. Nippon Nogeikagaku Kaishi 1998;72:153-157.
2) Kimura K, Ozeki M, Juneja LR, Ohira H. L-theanine reduces phychological and physiological stress responses. Biol Psychol 2007;74(1):39-45.
3) Kakuda T, Nozawa A, Unno T, et al. Inhibiting effects of theanine upon caffeine stimulation evaluated by EEG in the rat. Biosci Biotechnol Biochem 2000; 64:287-293.
Article 15
Asians have long been in the habit of drinking green tea after eating meals or sweets, insisting that it "makes their mouth clean." Now science has shown that this idea makes sense, as green tea can play an important part in fighting bacteria in th emouth, freshening the breath, warding off cavities and even protecting against root canals.
Dental trouble usually begins with Streptococcus mutans, the strain of bacteria primarily responsible for causing cacities. It clings to your teeth and uses the sugars in your mouth to produce a sticky, water-insoluble substance called plaque that coats your teeth. S. mutans and other bacteria then hang on to the plaque and convert sugars in your mouth to lactic acid, which eats away at your tooth enamel. It's the combination of plaque and acid that causes tooth decay. Luckily, green tea catechins can help fight the cavity-producting effects of S. mutans by:
* destroying a good percentage of the S. mutans bacteria themselves
* making the tooth surface more slippery, so the bacteria have a harder time clinging to the teeth
* inhibiting the production of plaque
* reducing the ability of bacteria to produce the enamel-eating acid
Suprisingly, it doesn't take quarts of tea to produce these benefits. Green tea catechins have destroyed S. mutans bacteria even when the catechins were at ower conceentrations than the amount found in one cup of tea. Tea is also naturally rich in flouride, the mineral that interacts with tooth enamel, hardening it and making it much less susceptible to decay. No wonder one study found that Japanese children who drank a cup of green tea immediately after lunch had significantly fewer cavities than those who didn't drink the tea!¹
But perhaps the most amazing effects of green tea involve the bacteria responsible for the dreaded root canal. In a "test-tube" study, 24 different bacterial strains were taken from the infected root canals of intact teeth.² The bacteria were then mixed with extracts taken from 4 different types of Japanese green tea (refined, ordinary, course and roasted). Amazingly, 21 of the 24 bacterial strains were either inhibited or completely destroyed by the green tea extracts. So how about topping off your next meal or snack with a cup of green tea? Your teeth will thank you for it!
Footnotes:
¹Kada T, Kaneko K, Matsuzaki S, et al. Detection and chemical identification of natural bio-antimutagens. A case of the green tea factor. Mutation Research 1985:150:127-132.
²Horiba N, Maekawa Y, Ito M, et al. A pilot study of Japanese green tea as a medicament: antibacterial and bacteridal effects. Journal of Endodontics 1991;17(3):122-24.
Too Much Fluoride?
Green Tea, like all teas made from the Camellia sinesis bush, contains flouride, a natural compound that hardens tooth enamel and helps prevent cavities. And that worries some people who think the American public is already "overly-flouridated." Flouride is often added to our drinking water, toothpaste, mouthwashes, and sometimes even our grape juice, and has been blamed for ailments ranging from allergies to cancer. Yet the Centers for Disease Control insists that the only downside to too much fluoride is the possibility of developing fluorosis, a permanent discoloration of the teeth caused by overexposure to fluoride when the teeth are just developing.
The Fluoride content of green tea leaves
For those who are still worried about the fluoride in green tea, here's what you need to know: Tea plants accumulate fluoride in their leaves over time, so the oldest leaves will contain the most fluoride, while the youngest will contain the least. Therefore, white tea (which is made from youngest leaves and buds) is your best bet if you're trying to take in as little fluoride as possible. Green tea that is made from older leaves, oolong tea and black tea have slightly more fluoride. The highest amount of fluoride is found in brick tea, a lower quality tea made from the oldest tea leaves which are molded into the shape of a brick (thus its name). Brick tea is the one to watch out for, as symptoms of fluorosis have been seen in Tibetan children and adults who drink large amounts of this kind of tea.
How much is too much?
To put the tea-fluoride question into perspective, consider that the DRI (Daily Recommended Amount) of fluoride is 3mg. An entire leter of green tea contains only about half that amount, or between 1.2 and 1.7mg. Black tea contains roughly the same amount of fluoride as green tea, and oolong tea contains slightly less. So even if you drink 7 eight-ounce cups of green, black or oolong tea every day, your fluoride intake will still be within the "safe zone."
For the super fluoride-conscious
But if you're still worried about the fluoride content of tea, here's an easy fix: Make your tea from white tea leaves and bottled water that doesn't contain fluoride. The fluoride content of tea that's prepared this way should be practically nonexistent.
Article 17
The Origins of Tea
For nearly 5,000 years people have been drinking and enjoying tea. But who discovered this delicious, health-promoting beverage? Credit typically goes to the Chinese Emperor Shen-Nung, also known as the "Divine Healer." According to legend, the Emperor was boiling a pot of water when some tea leaves blew in through the window and settled into the pot. Shen-Nung drank the resulting brew and the rest was history. The first written record of tea is found in Shen-Nung’s medical book the Pen Ts’ao, written in 2737 B.C., in which he noted that this remarkable beverage "quenches thirst. It lessens the desire for sleep. It gladdens and cheers the heart."
According to a different legend, tea was discovered by Dharma, the father of Zen Buddhism. In 520 A.D., so the legend goes, Dharma made the trek from India to China, where he demonstrated the Zen art of meditating by sitting in front of a wall for nine straight years. Not surprisingly, Dharma accidentally dozed off one day and when he woke up again he was so furious with himself that he vowed never to sleep again. To make good on this promise, he proceeded to cut off his eyelids! The bloody eyelids fell to the earth where they became the seeds of a tea plant from which a beverage could be made that lessened sleepiness.
Most likely, the true discovery of tea was made by the aboriginal natives living in what we now call Southeast Asia, where tea grows wild. The first historical record of tea was written in China in 350 A.D. by Kuo P’o, who was updating a Chinese dictionary. Kuo P’o added tea to the entries, describing it as "a beverage…made from the leaves by boiling." By this time, tea was prized as a medicine that could cure digestive disorders and nervous conditions. The tea leaves were also applied externally as a paste to ease the pains of rheumatism. But tea was not yet used as an everyday beverage.
As the desire for tea began to grow, a sufficient supply could not be collected just plucking the leaves off of nearby bushes. So tea plants began to be cultivated in the hills of Szechwan in central China, with the practice spreading throughout China and Japan courtesy of Buddhist priests. By the 5th century A.D., drinking tea for pleasure had become commonplace throughout China, and farmers typically dedicated a portion of their land to tea cultivation, while peasants often grew a few bushes in their gardens for private use. Thus, tea drinking became a part of daily life, even for the common people
Article 18
Taking a Break from a Stressed-Out World
Scientists the world over have confirmed that tea produces countless health-promoting effects. But most people don’t realize that the simple acts of making and drinking the brew may have their own beneficial effects. One Japanese study of more than 3,000 women over the age of 50 who regularly practiced the Japanese tea ceremony found that these women lived longer than those in a matched control group who didn’t perform the tea ceremony.¹ In a stressed-out world, it appears that the calming and relaxing ritual of boiling water, adding the leaves, inhaling the delicious aroma, and taking the time to sit down and slowly sip the tea may be almost as beneficial as the brew itself.
Of course, no one knows for sure whether it was the tea ceremony or the catechins, theanine or other health-promoting ingredients in green tea that relieved stress and prolonged the lives of the Japanese women in the study. What we do know is that stress is an invisible killer that contributes to cancer, heart disease, stroke and other deadly diseases. It unleashes a barrage of super-charged hormones like epinephrine, norepineprine and cortisol that increase blood pressure, release high levels of fat and sugar into the bloodstream, and break down muscle tissue. Eventually, stress can overwhelm the body’s immune system, leaving it vulnerable to disease. So keeping these powerful hormones at moderate levels is crucial to maintaining good health.
To test the ability of tea (in this case, black tea) to do this, scientists measured levels of the stress hormone cortisol in 75 healthy nonsmoking men.² The men were divided into two groups and given either tea or a similar, non-tea drink for six weeks, after which they were subjected to stress-inducing tasks. They found that those who had consumed the tea produced lower levels of cortisol and were more relaxed overall than those who had consumed the non-tea drink. The researchers concluded that drinking black tea may be able to speed recovery from the daily stresses in life and bring stress hormone levels back to normal.
Tea break, anyone?
Footnotes:
¹Sadakata S, Fukao A, Hisamichi S. Mortality among female practicioners of Chanoyu(Japanese "tea ceremony"). Tohoku J Exp Med 1992; 166:475-77. ²Steptoe A, Gibson EL, Vuononvirta R, et al. The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomised double-blind trial. Psychopharmacology (Berl.) 2007;(1):81-89.
Article 19
Is Green Tea a "Brain Food?"
Can green tea prevent or ease Alzheimer's disease, that devastating disease that can rob you of your ability to learn, reason, communicate, remember and carry out daily activities? Well, no one's saying that yet. But recent studies of the effects of green tea's catechins on animal brains are intriguing:
* Delayed brain aging
A study of mice genetically programmed to age rapidly found that taking in green tea catechins on a daily basis prevented oxidative damage to the DNA in their brain cells, slowed memory loss and delayed brain aging.¹
* Reversed mental deterioration
Another study of rapidly-aging mice measured the extent of their brain degeneration over time.² Mice that received green or oolong tea as their sole source of drinking fluid for 16 weeks reduced degenerative changes to their brains and actually reversed their mental deterioration. (These mice actually got smarter!)
* Improved memory-related learning
Long term administration of green tea catechins to young rats lowered levels of damaging free radicals in a part of the brain that's vital to memory processing.³ The catechin-consuming rats also experienced improved memory-related learning ability, compared to those that didn't receive the catechins.
* Less buildup of plaque
Finally, mice specially bred to develop Alzheimer's disease developed up to 54% less beta-amyloid buildup in their brains when they were given daily injections of the green tea catechin EGCg.4 Beta-amyloid plaques are believed to be a major cause of the brain cell death and dissue loss seen in Alzheimer's disease.
Of course, the big question still looms: Does green tea have the same effects in humans as it does in mice and rats? While few human studies of green tea's effects on brain function exist, one published in 2006 in the American Journal of Clinical Nutrition offers hope.5 Researchers gathered information from 1,003 Japanese men and women age 70+, measured their cognitive function, and tallied the frequency of their green tea consumption. After analyzing the data, the researchers concluded that, A higher consumption of green tea is associated with a lower prevalence of cognitive impairmenmt in humans." In other words, the more green tea they drank the less likely they were to have problems related to thinking and memory.
Footnotes:
1) Unno K, Takabayashi F, Yoshida H, et al. Daily consumption of green tea catechin delays memory regression in aged mice. Biogerontology 2007;8(2):89-95. 2) Chan YC, Hosoda K, Tsai CJ, Yamamoto S, et al. Favorable effects of tea on reducing the cognitive deficits and brain morphological changes in senescence-accelerated mice. Journal of Nutritional Science and Vitaminology (Tokyo) 2006;52(4):266-73.
3) Haque AM, Hashimoto M, Katakura M, et al. Long-term administration of green tea catechins improves spatial cognition learning ability in rats. Journal of Nutrition 2006;136(4):1043-47.
4) Rezai-Zadeh K, Shytle D, Sun N, et al. Green tea epigallocatechin-3-gallate (EGCG) modulates amyloid precursor protein cleavage and reduces cerebral amyloidosis in Alzheimer transgenic mice. Journal of Neuroscience 2005;25(38):8807-14.
5) Kuriyama S, Hozawa A, Ohmori K, et al. Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1. American Journal of Clinical Nutrition 2006:83(2):355-61.
Green Tea and Chronic Fatigue
Chronic fatigue syndrome (CFS) is a disease that can make you so tired and depressed that you may not be able to get through your normal daily tasks. This constant feeling of exhaustion is long-term (lasting more than 6 months), and any physical or mental activity intensifies the fatigue. Unfortunately, getting lots of rest probably won't improve the symptoms.
Although the cause of CFS is unclear, some studies have shown that it could be partially due to oxidative stress (the excess production of free radicals in the body). Since green tea has powerful free radical-quenching abilities, a team of researchers in India decided to find out whether the tea might also have anti-CFS effects.
In order to do this, they induced fatigue in mice specially bred to develop CFS by forcing them to swim in a water filled glass cylinder for 6 minutes a day for 7 straight days.¹ As expected, the mice developed signs of oxidative stress: their lipid peroxidation levels went up, while their levels of glutathione (the body's most powerful antioxidant) went down.
As the days went by, the mice also began to take on an "immobile posture" earlier and earlier in each swimming session. When mice are forced to swim in a container and can't escape, they quickly adopt a sort of "frozen" posture, moving only as much as they must to keep their heads above water. This immobile posture is believed to be a sign of despair or depression - an indication that the animals have given up hope of escaping.
So what happened when the mice were given green tea extract or green tea catechins? Compared to the mice in the control group, their lipid peroxidation levels were lower, their glutathione levels were restopred, and their increased immobility time was reversed. In other words, green tea protected the mice against oxidative stress and depression/despair, both of which are linked to CFS. The researchers concluded that green tea extract and catechins "could be used as potential agents in the management of CFS..."
Footnote:
¹Singal A, Kaur S, Tirkey N, et al. Green tea extract and catechin ameliorate chronic fatigue-induced oxidative stress in mice. J Med Food 2005;8(10):47-52.
Green Tea and Skin Cancer
You’ve probably seen “green tea extract” listed as an ingredient in skin care products, especially sunscreens. This makes perfect sense in light of the ever-growing scientific evidence suggesting that green tea can protect against skin cancer. Just be aware that most of the green tea/skin cancer studies have been conducted on animals, not humans. That’s because inducing skin cancer, a necessary step in testing the tea’s protective abilities, is unethical in human subjects. So instead, researchers use hairless mice because they have skin that is remarkably similar to human skin. When green tea extract is given to these mice before exposure to skin cancer carcinogens, either in their drinking water or painted on their skins, the results are nothing short of amazing:
Fewer skin tumors
For 50 days, two groups of mice were given drinking water that was either plain or contained green tea extract. Then both groups were injected with a powerful skin cancer inducer, followed by applications of a tumor promoter. The mice that received the green tea extract developed 44% fewer skin tumors.¹
Less tumor growth
Two groups of mice were injected with a skin cancer initiator. Then one group had a green tea catechin solution painted on their skins, while the other group was left alone. Both groups were then exposed to a tumor promoter. The mice that had the catechin solution painted on their skins had 50%-84% less tumor growth.²
Less tumor multiplication
Two groups of mice were exposed to UVB radiation three times a week for 24 weeks. Those that received green tea catechins in their drinking water had 35% fewer new tumors, 55% less tumor growth and 63% less tumor multiplication.³
Human studies
As any good researcher will tell you, the results gleaned from animal tests don’t necessarily translate to the same results in humans. And while there are few human studies of green tea’s effect on skin cancer, two are worth mentioning:
Melanoma inhibited
In a test-tube study of green tea’s effects on melanoma (a potentially deadly form of skin cancer), green tea extract decreased the growth and multiplication of the human melanoma cells and increased “cell suicide.”4
Radiation-induced skin toxicity decreased
In a study of 60 patients with cancer of the head, neck or pelvic region, tea extracts were painted on the patients’ skin before they received their radiation treatments. The tea extracts decreased the duration of skin toxicity, a common and painful side effect of radiation, by 5-10 days.5
While we certainly don’t suggest throwing out your sunblock in favor of sipping green tea, it looks like green tea does have the potential to be a very effective weapon in the war against skin cancer.
Footnotes:
¹ Wang ZY, Khan WA, Bickers DR, et al. Protection against polycyclic aromatic hydrocarbon-induced skin tumor initiation in mice by green tea polyphenols. Carcinogenesis 1989;10(2):411-15.
² Mukhtar H, Wang ZY, Katiyar SK, et al. Tea components: antimutagenic and anticarcinogenic effects. Preventive Medicine 1992;21(3):351-60.
³ Mantena SK, Meeran SM, Elmets CA, et al. Orally administered green tea polyphenols prevent ultraviolet radiation-induced skin cancer in mice through activation of cytotoxic T-cells and inhibition of angiogenesis in tumors. Journal of Nutrition 2005; 135(12):2871-77.
4 Nihal M, Ahmad N, Mukhtar H, et al. Anti-proliferative and proapoptotic effects of (-)-epigallocatechin-3-gallate on human melanoma. Int J Cancer 2005;114(4):513-21.
5 Pajonk F, Riedisser A, Henke M, et al. The effects of tea extracts on proinflammatory signaling BMC Med 2006;4:28.
Article 22
Bottled or Brewed?
Have you ever wondered if bottled green tea has the same health benefits as freshly brewed green tea? Well, sorry to break the news to all of you bottled tea drinkers, but in most cases the answer appears to be no.
In December 2006, the U.S. Department of Agriculture made public its database of the flavonoid content of foods.¹ (Flavonoids, a type of polyphenol, are a group of compounds found primarily in fruits and vegetables which act as powerful antioxidants. Green tea’s catechins are a sub-group of the flavonoids.) The USDA list, which includes the levels of catechins found in green tea prepared in different ways, is a real eye-opener for those who drink bottled tea for health reasons!
For example, the level of EGCg (green tea’s most potent catechin) in brewed loose-leaf tea was 78 mg per 100 grams of infusion. But ready-to-drink green tea (the kind that comes in a can or a bottle) contained a minuscule 4 mg of EGCg, 95 percent less than that found in freshly brewed green tea. And instant green tea was even worse, with a practically nonexistent .5mg EGCg!
Similar studies measuring the health-promoting compounds in green tea were done in 2005 by researchers at Oregon State University.² They found that the polyphenol content and antioxidant activity in some bottled tea products were 10 to 100 times lower than those found in brewed tea!
Why does bottled (or canned) green tea have such low levels of catechins? A major reason is that the catechins are sensitive to heat and oxygen, making them easy to destroy during the processing, transporting and storing of bottled tea. Also, many bottled tea products are made from tea extracts, which have far fewer antioxidants to begin with than brewed tea. To make matters worse, bottled tea products are often loaded with sugar or high fructose corn syrup which, besides being unhealthy and unnecessary, can contribute to catechin breakdown.
If you still want to drink bottled green tea, be sure to look for a high quality product made from brewed tea that contains no added sweeteners and has the polyphenol or catechin content listed on the label. Your best bet is a product that contains at least 75 mg polyphenols or 50 mg EGCg per cup. If you can’t find one, how about just settling for a nice cup of hot green tea?
Footnotes:
¹ http://www.nal.usda.gov/fnic/foodcomp/Data/Flav/Flav02-1.pdf (Scroll to database pages 87-88)
Article 23
The Eyes Have It!
The biggest natural threats to your eyesight are diseases that cause the degeneration of the retina, such as age-related macular degeneration and glaucoma. An important cause of retinal degeneration is oxidative stress (free radical damage). The good news is that recent studies have found that green tea, a potent antioxidant, may give the retina some much-needed protection.
Age-related macular degeneration, the leading cause of blindness in people over the age of 55, affects the part of your eye that allows you to see fine detail. It blurs the sharp, central vision you need for "straight-ahead" activities like reading, writing and driving. Glaucoma, the second leading cause of blindness, is actually a group of diseases that cause damage to the optic nerve.
Oxidative stress plays a part in both of these diseases. The retinal neurons, which send messages to the photoreceptor cells (rods and cones), become damaged by free radical generators like UV light and smoking. The free radicals attack the structure of your eye, wearing down its natural defense systems and leading to the death of cells in the retina. As a result, vision fades, sometimes to the point of being completely lost.
For a 2006 study published in Brain Research¹, res