by Неизвестный
Over thirty-five polyphenols have been identified to date. They include flavonoids, flavanols, flavanol glycosides, flavandiols, and phenolic acids. The dominant polyphenols in tea are known as catechins, and it is to them that most of the health benefits in tea are ascribed.
Scientific studies have shown that both animals and humans absorb catechins directly into the bloodstream, providing beyond a doubt that they are actually used by the body in various organs.6, 7In fact, catechins have been shown to glow as they go about their business of neutralizing free radicals!8 As antioxidants, in vitro studies show that catechins have the ability to halt enzymes that produce carcinogens and to inhibit cancer cell growth.
A study that measured catechins in tea extracts showed that green teas contained the highest percentage (26.7 percent), followed by oolong teas (23.2
percent), with black teas (4.3 percent) showing a dramatically decreased content.9 While instant teas have still fewer catechins, they nevertheless continue to exhibit some antimutagenic and antioxidant properties.10
Tea catechins may help to protect tea drinkers from several chronic health problems such as high blood cholesterol and high blood pressure.11, 12 Catechins make blood platelets less prone to abnormal clotting, a benefit that may reduce risk for both heart attack and stroke.13
Read Your Studies Carefully
As a nutritional biochemist, I am exposed to an endless stream of health-care “breakthroughs.” It seems like every week someone takes a substance (an esoteric biochemical -found in kumquats, for example) and adds it to a test tube containing a colony of cancer cells. When the cancer cells stop growing, people make the totally unscientific assumption that eating kumquats will cure cancer.
Remember that adding gasoline to a colony of cancer cells will stop cancer growth too, but that doesn’t mean we should drink gasoline. Besides, even if a substance is safe to ingest, you still need evidence that test-tube results will be duplicated in the human body. After all, few substances make it through the digestive system intact, and then there is the question of whether the active ingredient is even absorbed through the intestinal wall.
That’s why I carefully review all research concerning the health benefits of tea. When you read in the media that tea has just been shown to prevent cancer, it is important to examine the original research on which these claims are based.
Much of the information concerning anticancer benefits from tea polyphenols is derived from animal studies in which mice or rats are inoculated with certain types of cancer. Some are then given tea extract to see if it helps prevent the development of tumors. These studies often use extracts with polyphenol concentrations much greater than one would obtain from drinking tea.
Recently, there was great fanfare concerning the ability of tea to reduce risk for skin cancer. Newspaper reports suggested that readers start drinking green tea before exposure to summer sun. But in the actual research, the tea concentrate was applied topically.14 It’s also important to remember that tea can inhibit iron absorption enough to cause anemia.15 Likewise, it has been shown to inhibit thiamine (vitamin B-l) absorption and increase the loss of this vital nutrient enough to produce frank thiamine deficiency and signs of beriberi.16, 17
Tea has been shown to lower blood cholesterol levels, but to obtain any significant cholesterol benefits, you’d have to consume more than ten cups a day!18
Dig Deep Before You Leap
Can positive results from animal studies be generalized to humans? Perhaps, but to be sure, we need evidence that groups of people drinking tea have lower incidence of cancer compared to similar groups who don’t drink tea. The important word here is similar because, as I will explain, comparing people with different diets will give you meaningless information.
Epidemiologists are medical researchers who track the incidence of disease in various populations or geographic regions. Their studies regarding tea and cancer risk show mixed results, prompting the Working Group of the International Agency for Research on Cancer to conclude that the evidence for a cancer risk reduction from tea was inconsistent and inconclusive.19 Studies in Japan have shown that communities that consume large amounts of green tea daily have lower rates of stomach, esophageal, and liver cancer.20 But a study in China showed this protective effect only in women and not men. Confused, the Chinese group removed from their data anyone who smoked or drank alcohol.
When this variable was eliminated, consumption of green tea was associated with reduced risk for esophageal cancer.21 What’s going on?
I believe that this research illustrates a critical point regarding purported health benefits from herbs, foods, or beverages. We human beings are desperate to find substances that will protect us against disease. And let’s face it, there are also plenty of people looking for a way to make money. Thus when research suggests that something as simple as drinking tea will reduce your risk of cancer, everyone jumps on it. Sales of tea skyrocket, articles are printed in newspapers and magazines, and all the while, the epidemiologists are saying, “Hey wait a minute. …”
So why don’t people who smoke or drink appear to benefit from green tea? I believe it’s because green tea is a weak agent. It provides benefit to people whose diets are low in antioxidant fruits and vegetables, but it doesn’t provide sufficient antioxidants to protect someone who smokes or drinks. Thus, the accurate message here is not “Run to your grocery store and stock up on green tea,” it’s “Eat plenty of fruits and vegetables, and if you’re going to drink tea, make it green.”
Not to belabor the point, but a similar scenario resulted in the United States when Harvard researchers found that consumption of tomato sauce was
associated with decreased risk for prostate cancer.22 The popular interpretation of that data (reflected in newspaper headlines) was “Run out and eat pizza.” The more accurate message is, “The standard American diet is so pathetically low in antioxidants that even the tomato sauce on a pizza will confer some benefit.”
Now, I’m not saying that tomato sauce and green tea are not valuable. But they are weak agents, and we should not stake our hopes for avoiding cancer on these substances. The more prudent and proven approach is to reduce your intake of saturated fat and consume at least five servings of antioxidantrich fruits and vegetables daily. And if you want more protection, throw in a comprehensive nutritional supplement that provides the full range of antioxidant vitamins, minerals, and botanical extracts.
One More Perspective
Think of the British versus the Chinese. If the British, who have the largest per capita consumption of tea in the world, were experiencing lower rates of cancer, we’d have heard about it loud and clear. There are lots of studies showing the Chinese to have lower rates of certain cancers compared to Westerners, but once these same Chinese move to the West and start eating a Western diet, lo and behold, their cancer rates increase dramatically. Does tea help prevent cancer?
Green tea might, but black tea probably won’t, and in fact may be associated with increased risk for cancer of the colon, rectum, and lung.23
A Tip for Better Taste: Consider Brewing Loose-Leaf Tea People have become dependent on brewing tea using tea bags because they think it is easier. But tea leaves and herbs have to be cut very fine in order to fit into these small filter bags. These fine cuts, known as “fannings” or “dust,” are considerably lower in grade and quality than whole leaves. Black, green, and herb teas all suffer the same rapid loss of volatile components once they are cut so fine. Thus, the flavor you want in your tea cup tends to evaporate into the air long before you ever open your box of tea bags.
In the tea renaissance of the nineties, there has been a revival of brewing loose-leaf teas, and a variety of tea filters is now available. There are filters for single cups of tea and ones for teapots. There are French press pots originally designed for coffee but that work perfectly for tea. I bet you’ll find it is just as easy to brew loose-leaf tea, and you won’t believe the difference in flavor.
> Tea bags are great for traveling, but brew your tea from loose-leaf teas at home. (See Appendix B for sources of tea filters.)
Caffeine Is Still Caffeine
The good news about green tea is that it is lower in caffeine than black tea. The caffeine content in black tea is made more bioavailable during the fermentation process. The longer you brew your tea leaves, the more caffeine a cup of tea will have. A five-minute brew of black tea typically contains sixty to ninety milligrams of caffeine per six-ounce cup. A three-minute brew has about half that amount. A cup of green tea has approximately twenty-five milligrams per cup. The caffeine content is also affected by the cut size of the leaf you brew. If you use tea bags versus whole-leaf tea, you’ll end up with a lot more caffeine because the caffeine is released more readily from the smaller-cut leaf. By choosing what type and cut of tea you drink and how long you brew it, you can modify how much caffeine you ingest.
Green and Herbal Tea Blends
Suddenly everyone is marketing green teas blended with herbs. Why? The flavor of green tea is unappealing to the American palate, which is conditioned to expect tea to taste like black tea. Herbs enhance the flavor of green tea and add their own healthful properties. Most importantly, the addition of caffeine-free herbs to green tea cuts down on the amount of caffeine that ends up in your teacup.
Try some of the following blended green teas:
• The Republic of Tea: Organic green teas, Morrocan Mint, and Tea of Inquiry
• Yogi Tea: Wake Me Up Tea
• Tazo: Zen, Om and Green Ginger
• Celestial Seasonings: Green Tea with Antioxidants
Caffeine is caffeine no matter where you get it, and everything reported in this book regarding health disorders associated with caffeine applies to tea as well. Review the study presented in Chapter 6 in which women consuming high amounts of tea suffered 80 percent more PMS. If you are dependent on tea to get you going in the morning or give you a lift during the day, chances are you may be abusing caffeine and should reduce your daily intake.
Decaffeinated Tea
Unlike decaf coffee, decaf black tea has not been readily adopted by tea drinkers, and it seems to be simply a matter of taste. Coffee beans are decaffeinated before roasting, which reduces the flavor significantly, but not nearly as much as tea. The caffeine from tea is extracted after fermentation, and the dull, flavorless leaves are disdained by true tea lovers. Usually decaf tea is sold blended with flavors to give it some character. Unfortunately, because there are no standards set by the FDA for decaffeinated tea, manufacturers will sometimes add black tea to the decaf tea leaves to give them flavor, thus spiking the caffeine levels.
What concerns me a great deal more than the loss of taste, however, is the presence of chemical residue in decaf tea. There is no Swiss Water Process for decaffeinating tea leaves, so at this point, the only method available is the solvent process. One study showed that residues of methylene chloride (a known carcinogen) were four times (400 percent) higher in decaf tea compared to decaf coffee.24
Caffeine-free Herbal Teas
While herbal teas became popular in the seventies with the introduction of delicious herbal blends, people have been brewing leaves, fruits, flowers, roots, barks, and berries for millennia. The word tea is now commonly thought of as a hot brewed beverage and no longer is it the exclusive domain of the Camellia sinensis plant. Instead we have black tea, green tea, and herbal tea, which comes in a great diversity of types and flavors. Of the three, only herbal tea is caffeine free, but you still have to be careful. Some herbs, like maté (yerba maté), kola nut, bissy nut, and guarana, contain caffeine and may not be labeled as such.
Although there are over 3,000 varieties of black tea, most people’s taste buds couldn’t tell the difference between many of them. With herbal teas, though, you get quite a range of flavors. There are several hundred different leaves, fruits, flowers, roots, barks, and berries in commerce that an herb tea company can use to create its blends.
A true medicinal tea that is used to produce a specific effect on one’s health is usually brewed differently than the herb teas you buy in the grocery store. For instance, if you visit a Chinese herbalist for help with a medical condition, you’ll
instance, if you visit a Chinese herbalist for help with a medical condition, you’ll be given a bag of roots, barks, leaves, or even mushrooms to take home and simmer on your stove for up to a half an hour depending on the herbs. You can imagine that this brew, which is called a decoction by medicinal herbalists, won’t be pleasant tasting or smelling, but you’d only have to drink it for a period of time until your health improves. Herbal teas, on the other hand, with their smaller dosage of herbs per cup of tea, have more generalized health-promoting properties. They are designed to be drunk daily if desired without producing any side effects. Herbal teas can be soothing when you’re suffering from minor symptoms, but they are primarily formulated for taste enjoyment and general health enhancement.
Since there is such a wide variety of herb teas sold on the market, it is helpful to classify them according to type. Once you know what’s available, it’s easier to make a selection of the kind of tea you might want to drink. You’ll find that it’s great to have a variety of herbal teas on hand to suit different moods, weather, and occasions. Here are some of my favorites. Enjoy them hot or iced!
IMMUNE-STIMULATING BLENDS
This is the type of herbal tea I drink most frequently. After all, on a day-to-day basis, we mostly need to keep our good health intact. If I feel “immune challenged” or I want to start my day with an immune boost, I’ll drink a cup of a blend that contains any of the following tonic herbs, known as adaptogens (herbs that strengthen or enhance the immune system, nervous system, and/or glandular system while they help the body cope with stress): Siberian ginseng, Panax ginseng, astragalus, shizandra, echinacea, ashwagandha, reishi mushrooms, licorice. Some of my favorite brands include:
• The Republic of Tea: Ginseng Peppermint and Organic Temple of Health
• Traditional Medicinals: Echinacea Plus, Reishi Defense, and Double Ginseng
• Celestial Seasonings: Emperor’s Choice, Echinacea Herb, and Ginseng Plus
• Yogi Tea: Ginseng NRG Tea and Echinacea Special Formula DIGESTIVE TEAS
One of the main reasons people started experimenting with herbs was to help their digestion. Fortunately, many herbs have digestive-stimulating properties.
They can help relieve gas and heartburn, stimulate the flow of gastric juices, relax spasms and cramps, and dispel nausea or queasiness. Look for digestive blends that have any of the following herbs: ginger, anise seeds, thyme, chamomile, hyssop, peppermint, spearmint, lemon balm, fennel, coriander, chicory, catnip, and cardamom. Bitter herbs such as gentian, artichoke, dandelion, and angelica are often found in herbal digestive bitters but not in tea.
My favorite digestive teas feature ginger and/or mint, like the following brands.
• The Republic of Tea: Orange Ginger Mint and Organic Mint Fields • Traditional Medicinals: Ginger Aid and Eater’s Digest • Celestial Seasonings: Grandma’s Tummy Mint and GingerEase • Yogi Tea: Lemon Ginger, Stomach E-Z, and Ginger Tea
• Tazo: Refresh
SEDATIVE TEAS
The number-one best-selling herbal tea in the United States is Celestial Seasonings, Sleepytime herb tea. Why? I guess after a day filled with caffeine and stress, Americans need help slowing down enough to fall asleep. Sedative teas are mild in action, again due to dose. You can’t make a drinkable herb tea with a significant amount of sedative herbs because most don’t taste very good.
However, sedative teas can help you relax, and if you need extra help, try herbal extracts made from sedative herbs, too. The classic sedative herbs include: chamomile, hops, linden flowers, lavender, passion flower, skullcap, and valerian. Some lesser-known sedative herbs are tilia buds and white zapote from Mexico. I recommend:
• The Republic of Tea: Chamomile Lemon
&nb
sp; • Traditional Medicinals: Nighty Night
• Celestial Seasonings: Sleepytime
• Ygi Tea: Bedtime Tea
STRESS-RELIEF TEAS
Tnese teas differ from sedative teas because they are designed to help you cope with stress but not become sleepy. Two herbs stand out in this arena that have completely different actions from one another. Siberian ginseng, also called eleuthero ginseng, has been shown in both animal and human studies to help the body cope with stress.25 Kava, a muscle relaxant with a long tradition of use in the South Pacific, can actually help relieve overtense muscles.26 Kava is one of the new stars on the herbal market, and you’ll find it in nutritional supplements and herbal extracts as well as teas. You may want to drink Siberian ginseng tea frequently, but kava should be saved for those times when you really need help relaxing and letting go.
For starters:
• The Republic of Tea: Ginseng Peppermint
• Celestial Seasonings: Tension Tamer
• Yogi Tea: Kava Kava Special Formula and Calming Tea
STIMULATING SPICE TEAS
Spices have long been valued for their flavor and stimulating properties. The spice trade fueled world exploration as Europeans competed to find exotic flavors and dominate spice-growing regions. Once spices were as rare and dear as gold, but now, who could imagine a kitchen without cinnamon, black pepper, and ginger? Spicy herbal teas will warm you internally and stimulate your digestion and elimination. Spice teas have been popular for a long time, but the latest entries into the marketplace are the spicy “chai” teas inspired by Indian’s custom of drinking black teas heavily sweetened and flavored with spice and milk. Chai teas come both as liquid concentrates and as teas to brew. Some chai brands are marketing all-herbal blends that are caffeine free. Spice teas in general require a longer brewing time and are best simmered for ten minutes to bring out their spicy flavor. They can be mixed with milk just like black tea.