You've heard about green tea's health benefits. Read the details here, reprinted from an article in Tea Magazine.
Tea is a drink whose time has come — again.
In the American colonies, tea was the most popular beverage until England's efforts to monopolize the tea trade, undercut American tradesmen, and capitalize on tea taxes turned the colonists against it. Besides throwing British tea into the Boston Harbor, the Americans expressed their rebellion by switching to a thicker, more bitter source of caffeine: coffee. But the Tea Tax no longer exists, and there are good reasons to switch back — not political this time, but scientific.
For years, studies in China and Japan have shown that the folklore about tea does contain some truth — it does promote longer life. In lung-cancer experiments with rats, the rats drinking green tea had only half the cancer rate as the non-tea-drinking rats. In other animal experiments, green tea was found to protect against colon cancer, skin cancer, stomach cancer, and breast cancer.
Japanese smokers have only half the lung cancer rate as American smokers. In areas of Japan where the most tea is drunk, the rate of stomach cancer (a big killer in Japan) is the lowest. In a study of 6000 Japanese women, those who drank five cups or more of green tea per day cut their risk of strokes by 50%.
GREEN EAST VERSUS BLACK WEST
In the West, we've been slow to study tea because, even with the increase in the popularity of tea, merchants still sell four times as much coffee. In addition, the studies emanating from Asia are about green tea, and Westerners customarily drink black tea.
Does black tea have the same health-promoting effect? Zhi-Yuan Wang of Rutgers University wanted to find out. He gave mice some carcinogens that normally cause skin tumors. A fourth of his mice were given green tea, a fourth got black tea, another fourth got decaffeinated black, and the last fourth got plain water. Sure enough, the green-tea-drinking mice developed 70% fewer tumors than the water drinkers. SEVENTY PERCENT FEWER! These are the kinds of findings that have awakened so much interest in tea. The numbers are big.
There are a lot of things people can do to improve their health, but usually the effect of any one of them is relatively small. Tea is different. For something so easy and pleasant to do, it is startling how great a difference it can make. The good news for us black tea lovers is the the black-tea-drinking mice also had 70% fewer tumors than the water drinkers. The decaf-tea drinkers had 60% fewer tumors — still a good showing.
RESEARCH ACCELERATION
Many studies are now being done in the West. Not only does tea reduce the rate of the cancers already mentioned, but it lowers the incidence of esophageal and liver cancers, too — also by dramatic amounts. And there is even more good news: tea lowers the risk of heart disease.
The two deadliest diseases for Americans are cancer and heart disease, and here is one substance — a substance that is easily available, inexpensive, and contains no calories — that lowers the incidence of both, and by a large margin!
A fifteen-year study in the Netherlands on 552 Dutch men aged 50-69 found that those who drank more than two cups of (in this case, black) tea daily were 50% less likely to have a fatal heart attack. The same study found that those who drank five cups of tea a day were 69% less likely to suffer a stroke than those men who only drank half as much tea.
In a study at the University of Southern California School of Medicine, elderly people who drank more than two cups of tea per day and had done so for a long time had a 63% lower risk of pancreatic cancer than people who had drunk less than a cup per day. The Norwegian government did a large-scale study (20,000 people) and found that the overall death rate was lower for those who drank at least one cup of tea per day.
Studies in both Norway and Israel have found that tea drinkers have lower blood cholesterol. This partially explains the reduced risk of heart disease and stroke, but it's even better than that: studies have shown that LDL, the "bad" cholesterol, only clogs arteries when it is damaged by oxidation. Tea is full of phytochemicals (chemicals found in plants) which act as powerful antioxidants. In a test-tube study of 39 food-derived antioxidants, the phytochemicals in tea were the most potent inhibitors of LDL oxidation. In fact, one compound in tea was found to be 20 times stronger than the potent antioxidant vitamin C.
One of the antioxidants in green tea is epigallocatechin gallate (EGCG); when you brew a cup and then let the water evaporate, half of what you have left is EGCG. Fifty percent of the solid matter of a cup of tea is a potent antioxidant.
We've all heard that a glass of red wine per day is good for us, primarily because of its antioxidants, one of the most potent being catechins. Let's compare tea with wine: a glass of red wine contains 300 milligrams of catechins; a cup of black tea, 210 milligrams. That's quite good; but the winner is green tea, with a whopping 375 milligrams per cup, and you can drive home afterwards.
A Dutch study of some 800 men found that those who had the most flavonoids (another kind of phytochemical) in their diet were 66% less likely to develop heart disease than those who consumed the least. For those who got the most flavonoids, their main source was black tea.
Research is exploding to the point where previous studies are being re-examined. The famous "Seven Countries Study" done in the 1960s has been re-analyzed in light of what we now know about tea. This study achieved fame because it was the first to show that the amount of fat in the diet affects heart disease. Re-analyzed, it seems that a high intake of antioxidants, mainly from tea, explains the lower incidence of heart disease in the tea-drinking countries.
An assistant professor at the University of Minnesota, Wei Zheng, MD, PhD, studied the tea-drinking habits of 35,369 postmenopausal women. Over an eight-year period, the women who drank at least two cups of tea per day had 32% fewer cancers of the digestive tract (including colon and esophagus) than women who only drank tea occasionally or never. They were also 60% less at risk from cancers of the bladder and kidneys. The women who drank at least four cups of tea had even fewer of these cancers.
ANTIOXIDANTS AND BEYOND
The ways in which tea produces its healthy effects go on and on. Women's livers metabolize estrogen and then send it through the gall bladder into the bile to be eliminated. Certain kinds of bacteria in the intestines change that estrogen into a potent cancer-producing hormone, which is then reabsorbed by the intestines, contributing to the development of breast cancer. Studies show that tea stops those bacteria from changing the estrogen into something dangerous, according to Herb Piersen, PhD, former director of the National Cancer Institute's Designer Foods Program.
Another way tea creates a healthy effect is by neutralizing nitrosamines (from cured meats) and heterocyclic amines (from cooked meats). "Drinking tea with meals in Japan and China," says a cancer researcher at the University of British Columbia, "is thought to be a major reason for the low cancer rates in these countries."
Tea also helps prevent tooth decay in several ways. It contains a solid dose of fluoride, and according to researchers at the Tokyo Dental College, it fights the kinds of bacteria in the mouth that cause gum disease and the eventual loss of the teeth. It worked better, in fact, than the antibiotic tetracycline. It also kills Streptococcus mutans, the greatest cavity-causing bacteria in the mouth.
Substances in green tea also lower hypertension in mice. The findings go on and on. In the test-tube, tea inhibits the proliferation of viruses, including influenza.
There is a downside to tea: it increases the passage of B and C vitamins and calcium through the body, although not very much. If you take a vitamin-mineral supplement, you're probably getting enough extra B and C vitamins to neutralize this effect.
One of the paradoxically valuable things about tea is that it contains caffeine. Caffeine is addicting. Once you start drinking tea, you tend to do so regularly, and this turns out to be a good thing. It keeps an uninterrupted flow of antioxidants going through your cells, cleaning up the damaging oxygen, killing dangerous bacteria, neutralizing carcinogens, lowering your cholesterol, preventing cancer, and keeping your veins from clogging.
Americans turned away from tea as a rebellion against oppression. Now we're switching back. Times are changing, and so are we — for the better, for our health. We have a new slogan: Drink your TEA. It does a body good.
Editor's note: Iced tea works as well as hot tea in bestowing healthy benefits, as long as it is brewed and not instant iced tea. Iced tea is an American invention and very rare in the rest of the world, but 80% of the tea Americans drink is iced.
This article originally appeared in TEA a magazine in the June/July 1997 issue.
A study by Purdue University researchers discovered that tea reduces the amount of mercury from fish you body digests. One of the dangers of eating fish is that it contains the heavy metal, mercury. In the study, when people were given a tea extract along with mackerel, up to 92 percent less mercury was absorbed than those who ate fish without the tea extract.
They tried both black and green tea extracts, which both worked well. Green tea extract worked a little better.
Adam Khan is the author of Principles For Personal Growth, Slotralogy, Antivirus For Your Mind, and co-author with Klassy Evans of How to Change the Way You Look at Things (in Plain English). Follow his podcast, The Adam Bomb.
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