Jul 20, 2008

- Green Tea and Health Conditions


Green tea has been extensively studied in people, animals, and laboratory experiments. Results from these studies suggest that green tea may be useful for the following health conditions:

Atherosclerosis

Population-based studies indicate that the antioxidant properties of green tea may help prevent atherosclerosis, particularly coronary artery disease. (Population-based studies means studies that follow large groups of people over time and/or studies that are comparing groups of people living in different cultures or with different dietary habits, etc.) In May 2006, however, the U.S. Food and Drug Administration (FDA) rejected a petition from teamakers to allow tea labels to claim that green tea reduces the risk of heart disease. The FDA concluded that there is no credible evidence to support qualified health claims for green tea or green tea extract reducing the risk of heart disease.

High cholesterol

Research shows that green tea lowers total cholesterol and raises HDL ("good") cholesterol in both animals and people. One population-based study found that men who drink green tea are more likely to have lower total cholesterol than those who do not drink green tea. Results from one animal study suggest that polyphenols in green tea may block the intestinal absorption of cholesterol and promote its excretion from the body. In another small study of male smokers, researchers found that green tea significantly reduced blood levels of harmful LDL cholesterol.

Cancer

Several population-based studies have shown that green tea helps protect against cancer. For example, cancer rates tend to be low in countries such as Japan where people regularly consume green tea. However, it is not possible to determine from these population-based studies whether green tea actually prevents cancer in people. Emerging studies suggest that the polyphenols in green tea may play an important role in the prevention of cancer. Researchers also believe that polyphenols help kill cancerous cells and stop their progression.

Bladder cancer. Only a few studies have examined the relationship between bladder cancer and green tea consumption. In one study that compared people with and without bladder cancer, researchers found that women who drank black tea and powdered green tea were less likely to develop bladder cancer. A follow-up study by the same group of researchers revealed that bladder cancer patients (particularly men) who drank green tea had a substantially better 5-year survival rate than those who did not.

Breast cancer. Studies in animals and test tubes suggest that polyphenols in green tea inhibit the growth of breast cancer cells. In one study of 472 women with various stages of breast cancer, researchers found that women who consumed the most green tea experienced the least spread of cancer (particularly premenopausal women in the early stages of breast cancer). They also found that women with early stages of the disease who drank at least 5 cups of tea every day before being diagnosed with cancer were less likely to suffer recurrences of the disease after completion of treatment. However, women with late stages of breast cancer experienced little or no improvement from drinking green tea. In terms of breast cancer prevention, the studies are inconclusive. In one very large study from Japan, researchers found that drinking green tea was not associated with a reduced risk of breast cancer.

Ovarian cancer. In a study conducted on ovarian cancer patients in China, researchers found that women who drank at least one cup of green tea per day survived longer with the disease than those who didn’t drink green tea. In fact, those who drank the most tea, lived the longest.

Colorectal cancer. Studies on the effects of green tea on colon or rectal cancer have produced conflicting results. Some studies show decreased risk in those who drink the tea, while others show increased risk. Further research is needed before researchers can recommend green tea for the prevention of colorectal cancer.

Esophageal cancer. Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells. However, studies in people have produced conflicting findings. For example, one large-scale population-based study found that green tea offered significant protection against the development of esophageal cancer (particularly among women). Another population-based study revealed just the opposite -- green tea consumption was associated with an increased risk of esophageal cancer. In fact, the stronger and hotter the tea, the greater the risk. Given these conflicting results, further research is needed before scientists can recommend green tea for the prevention of esophageal cancer.

Lung cancer. While green tea polyphenols have been shown to inhibit the growth of human lung cancer cells in test tubes, few studies have investigated the link between green tea consumption and lung cancer in people and even these studies have been conflicting. One population-based study found that Okinawan tea (similar to green tea but partially fermented) was associated with decreased lung cancer risk, particularly among women. A second study revealed that green tea and black tea significantly increased the risk of lung cancer. As with colon and esophageal cancers, further studies are needed before researchers can draw any conclusions about green tea and lung cancer.

Pancreatic cancer. In one large-scale study researchers compared green tea drinkers with non-drinkers and found that those who drank the most tea were significantly less likely to develop pancreatic cancer. This was particularly true for women -- those who drank the most green tea were half as likely to develop pancreatic cancer as those who drank less tea. Men who drank the most tea were 37% less likely to develop pancreatic cancer. However, it is not clear from this population-based study whether green tea is solely responsible for reducing pancreatic cancer risk. Further studies in animals and people are needed before researchers can recommend green tea for the prevention of pancreatic cancer.

Prostate cancer. Laboratory studies have found that green tea extracts prevent the growth of prostate cancer cells in test tubes. In a large study conducted in Southeast China researchers found that the risk of prostate cancer declined with increasing frequency, duration and quantity of green tea consumption. However, both green and black tea extracts also stimulated genes that cause cells to be less sensitive to chemotherapy drugs. Given this potential interaction, people should not drink black and green tea (as well as extracts of these teas) while receiving chemotherapy.

Skin cancer. The main polyphenol in green tea is epigallocatechin gallate (EGCG). Scientific studies suggest that EGCG and green tea polyphenols have anti-inflammatory and anti-cancer properties that may help prevent the onset and growth of skin tumors.

Stomach cancer. Laboratory studies have found that green tea polyphenols inhibit the growth of stomach cancer cells in test tubes, but studies in people have been less conclusive. In two studies that compared green tea drinkers with non-drinkers, researchers found that people who drank tea were about half as likely to develop stomach cancer and gastritis (inflammation of the stomach) as those who did not drink green tea. However, a study including more than 26,000 men and women in Japan found no association between green tea consumption and stomach cancer risk. Some studies even suggest that green tea may increase the risk of stomach cancer.

Further studies are underway to determine whether green tea helps reduce the risk of stomach cancer. Although green tea is considered safe for people at risk for stomach cancer, it is too soon to tell whether green tea reduces the likelihood of developing this disease.

Inflammatory Bowel Disease (IBD)

Green tea may help reduce inflammation associated with Crohn's disease and ulcerative colitis, the two types of IBD. If green tea proves to be helpful for preventing colon cancer, this would be an added benefit for those with IBD because they are at risk for colon cancer.

Diabetes

Green tea has been used traditionally to control blood sugar in the body. Animal studies suggest that green tea may help prevent the development of type 1 diabetes and slow the progression once it has developed. People with type 1 diabetes produce little or no insulin, a hormone that converts glucose (sugar), starches, and other foods into energy needed for daily life. Green tea may help regulate glucose in the body.

Liver disease

Population-based studies have shown that men who drink more than 10 cups of green tea per day are less likely to develop disorders of the liver. Green tea also seems to protect the liver from the damaging effects of toxic substances such as alcohol. Animal studies have shown that green tea helps protect against the development of liver tumors in mice.

Results from several animal and human studies suggest that one of the polyphenols present in green tea, known as catechin, may help treat viral hepatitis (inflammation of the liver from a virus). In these studies, catechin was isolated from green tea and used in very high concentrations. It is not clear whether green tea (which contains a lower concentration of catechins) confers these same benefits to people with hepatitis.

Weight loss

Studies suggest that green tea extract may boost metabolism and help burn fat. One study confirmed that the combination of green tea and caffeine improved weight loss and maintenance in overweight and moderately obese individuals. However, a second study found that weight maintenance following weight loss was not affected by green tea. Some researchers speculate that substances in green tea known as polyphenols, specifically the catechins, are responsible for the herb's fat-burning effect.



(ummedu)

Jul 9, 2008

- Green Tea Miracles


"Better to be deprived of food for three days, than tea for one." (Ancient Chinese Proverb)

Is any other food or drink reported to have as many health benefits as green tea? The Chinese have known about the medicinal benefits of green tea since ancient times, using it to treat everything from headaches to depression. In her book Green Tea: The Natural Secret for a Healthier Life, Nadine Taylor states that green tea has been used as a medicine in China for at least 4,000 years.

Benefits of Green Tea

There are four primary polyphenols in green tea and they are often collectively referred to as catechins.

Powerful antioxidants, catechins have been shown in recent studies to fight viruses, slow aging, and have a beneficial effect on health. Clinical tests have shown that catechins destroy free radicals and have far-reaching positive effects on the entire body.

Free radicals are highly reactive molecules and fragments of molecules that can damage the body at the cellular level leaving the body susceptible to cancer, heart disease, and many other degenerative diseases.

EGCG is a potent antioxidant.

Epigallocatechin gallate (EGCG), an antioxidant found in green tea, is at least 100 more times more effective than vitamin C and 25 times more effective than vitamin E at protecting cells and DNA from damage believed to be linked to cancer, heart disease and other serious illnesses. This antioxidant has twice the benefits of resveratrol, found in red wine.

Special Benefits of Green Tea

  • Reduces high blood pressure. Drinking green tea represses angiotensin II which leads to high blood pressure.

  • Lowers blood sugar. Green tea polyphenols and polysaccharides are effective in lowering blood sugar.

  • Fights cancer. There have been many studies that have shown that green tea catechins are effective at preventing cancer.

Green tea also boosts the immune system because of its high concentrations of polyphenols and flavenoids.

Green tea antioxidants have been shown to lower cholesterol.


Today, scientific research in both Asia and the west is providing hard evidence for the health benefits long associated with drinking green tea. For example, in 1994 the Journal of the National Cancer Institute published the results of an epidemiological study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly sixty percent. University of Purdue researchers recently concluded that a compound in green tea inhibits the growth of cancer cells. There is also research indicating that drinking green tea lowers total cholesterol levels, as well as improving the ratio of good (HDL) cholesterol to bad (LDL) cholesterol.

To sum up, here are just a few medical conditions in which drinking green tea is reputed to be helpful:

  • cancer
  • rheumatoid arthritis
  • high cholesterol levels
  • cariovascular disease
  • infection
  • impaired immune function

What makes green tea so special?

The secret of green tea lies in the fact it is rich in catechin polyphenols, particularly epigallocatechin gallate (EGCG). EGCG is a powerful anti-oxidant: besides inhibiting the growth of cancer cells, it kills cancer cells without harming healthy tissue. It has also been effective in lowering LDL cholesterol levels, and inhibiting the abnormal formation of blood clots. The latter takes on added importance when you consider that thrombosis (the formation of abnormal blood clots) is the leading cause of heart attacks and stroke.

Links are being made between the effects of drinking green tea and the "French Paradox." For years, researchers were puzzled by the fact that, despite consuming a diet rich in fat, the French have a lower incidence of heart disease than Americans. The answer was found to lie in red wine, which contains resveratrol, a polyphenol that limits the negative effects of smoking and a fatty diet. In a 1997 study, researchers from the University of Kansas determined that EGCG is twice as powerful as resveratrol, which may explain why the rate of heart disease among Japanese men is quite low, even though approximately seventy-five percent are smokers.

Why don't other Chinese teas have similar health-giving properties? Green, oolong, and black teas all come from the leaves of the Camellia sinensis plant. What sets green tea apart is the way it is processed. Green tea leaves are steamed, which prevents the EGCG compound from being oxidized. By contrast, black and oolong tea leaves are made from fermented leaves, which results in the EGCG being converted into other compounds that are not nearly as effective in preventing and fighting various diseases.


Other Benefits

New evidence is emerging that green tea can even help dieters. In November, 1999, the American Journal of Clinical Nutrition published the results of a study at the University of Geneva in Switzerland. Researchers found that men who were given a combination of caffeine and green tea extract burned more calories than those given only caffeine or a placebo.

Green tea can even help prevent tooth decay! Just as its bacteria-destroying abilities can help prevent food poisoning, it can also kill the bacteria that causes dental plaque. Meanwhile, skin preparations containing green tea - from deodorants to creams - are starting to appear on the market.

Harmful Effects?

To date, the only negative side effect reported from drinking green tea is insomnia due to the fact that it contains caffeine. However, green tea contains less caffeine than coffee: there are approximately thirty to sixty mg. of caffeine in six - eight ounces of tea, compared to over one-hundred mg. in eight ounces of coffee.

(about)

Jul 5, 2008

- Foods That Fight Disease-4

Bone-Building Foods

The road to strong bones is paved with calcium-rich food. Leafy green vegetables and low-fat dairy products are excellent sources of calcium, the mineral that puts stiffness into your skeletal system and keeps your bones from turning rubbery and fragile.

Your body uses calcium for more than keeping your bones strong. Calcium permits cells to divide, regulates muscle contraction and relaxation, and plays an important role in the movement of protein and nutrients inside cells. If you don't absorb enough from what you eat to satisfy these requirements, your body will take it from your bones. Because your body doesn't produce this essential mineral, you must continually replenish the supply. Even though the recommended daily amount is 1,200 mg, most adults don't eat more than 500 mg.

One reason may have been the perception that calcium-rich dairy products were also loaded with calories. "In the past, women, in particular, worried that dairy products were high in calories," says Letha Y. Griffin, M.D., of Peachtree Orthopaedics in Atlanta. "But today you can get calcium without eating any high-fat or high-calorie foods by choosing skim milk or low-fat yogurt." Also, low-fat dairy products contain phosphorous and magnesium and are generally fortified with vitamin D, all of which help your body absorb and use calcium.

If you find it difficult to include enough calcium in your diet, ask your doctor about supplements. They're a potent way to get calcium as well as vitamin D and other minerals. But there's a downside. If you rely on pills in lieu of a calcium-rich diet, you won't benefit from the other nutrients that food provides. Getting the recommended vitamin D may be easy, since your body makes the vitamin when your skin is exposed to the sun's rays.

(RD)

Jul 1, 2008

- Foods That Fight Disease-3

Heart-Saving Foods

No other part of your body benefits more from good dietary choices than your cardiovascular system. What you eat, and choose not to eat, has a dramatic effect on your risk for heart disease and stroke.

Saturated fat, found mostly in meat and full-fat dairy products, is the major culprit in raising blood cholesterol, the main ingredient of artery-clogging plaque. Overindulging in these foods raises the risk of developing heart disease. But you can lower this risk by shifting the emphasis so that nutrient- and fiber-rich foods such as fruits, vegetables, and grains make up approximately two-thirds of what you eat each day.

Plant-based foods provide complex carbohydrates as well as vitamins and minerals. And they contain very little fat. Because they're rich in indigestible fiber, they take up space in the intestines, which can help you control your appetite -- and your weight.

These foods have another advantage. "When you look at non-drug alternatives to reduce cholesterol," says registered dietitian Linda Van Horn, Ph.D., of Northwestern University Medical School in Chicago, "you find that a high-fiber component to a low-fat diet is very effective." Soluble fiber, in particular, has a direct bearing on the body's production, regulation, and elimination of cholesterol. Although the reasons aren't entirely clear, it may be that soluble fiber combines with intestinal fluids to form a gel that binds to fat or prevents it from being absorbed into the bloodstream. Whatever the reason, it does work. One study found that by increasing the amount of soluble fiber they ate, people with Type 2 diabetes decreased their cholesterol levels by almost 7 percent. Other studies show that simply adding two servings a day of oats or other cereals high in soluble fiber can reduce cholesterol levels by almost 3 to 4 percent in people without diabetes. These two servings represent only a small portion of the recommended six to 11 daily servings of bread, cereals, grains, and pasta.

While fiber is the most important dietary adjunct in controlling blood cholesterol, fiber-rich foods contain other nutrients, including antioxidants and phytochemicals, which researchers believe also deter the buildup of plaque in arteries. But the mechanism is unclear. "Is it the nutrients in these foods that have a positive effect, or is it that the more of them you eat, the less fat-laden food you consume?" asks Alice H. Lichtenstein, D. Sc., of the USDA Human Nutrition Research Center at Tufts University in Boston. "We don't know the answer right now, but it's probably a combination of both."

What is clear is that you can eat a heart-healthy diet and still include some fat. "We've made people aware of cholesterol and fat," says Sayed F. Feghali, M.D., a cardiologist at the Texas Heart Institute in Houston. "There's no question that saturated fat is the villain when it comes to cholesterol buildup in blood vessels. But we need some fat. We cannot function on a zero-fat diet."

So be judicious in your choices. Restrict meat and dairy products to less than 10 percent of your daily calories. Try poultry, dried beans, eggs, and nuts for protein and energy. Soy products, when substituted for animal protein, show promise in reducing LDL ("bad") cholesterol. Substitute heart-healthy monounsaturated oils, such as olive, canola, and peanut, for saturated and hydrogenated fats.

Also, watch out for the words "hydrogenated" or "partially hydrogenated" on baked goods and snack foods. They indicate that otherwise heart-healthy unsaturated fat has been manipulated so that oils that would normally be liquid at room temperature stay solid. The process yields trans fats, which raise both total and LDL cholesterol.

Finally, don't be so preoccupied with fat that you lose sight of calories. It's too many calories that add unwanted weight, which can put a strain on your heart. If you're stumped about striking a reasonable dietary balance, check out the eating plans of the American Heart Association (www.americanheart.org).

(RD)
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