Green Tea

Green tea has been consumed throughout the ages in India, China, Japan, and Thailand. In traditional Chinese and Indian medicine, practitioners used green tea as a stimulant, diuretic (to promote the excretion of urine), astringent (to control bleeding and help heal wounds), and to improve heart health. Other traditional uses of green tea include treating flatulence (gas), regulating body temperature and blood sugar, promoting digestion, and improving mental processes.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 clinical 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 or studies that are comparing groups of people living in different cultures or with different dietary habits.) 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 clinical 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 clinical 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 clinical 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 clinical 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 clinical 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. Clinical 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 clinical study from Japan, researchers found that drinking green tea was not associated with a reduced risk of breast cancer.

Ovarian cancer. In a clinical 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. Clinical studies on the effects of green tea on colon or rectal cancer have produced conflicting results. Some clinical 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, clinical studies in people have produced conflicting findings. For example, one large-scale population-based clinical study found that green tea offered significant protection against the development of esophageal cancer (particularly among women). Another population-based clinical 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 clinicial studies have investigated the link between green tea consumption and lung cancer in people and even these studies have been conflicting. One population-based clinical study found that Okinawan tea (similar to green tea but partially fermented) was associated with decreased lung cancer risk, particularly among women. A second clinical study revealed that green tea and black tea significantly increased the risk of lung cancer. As with colon and esophageal cancers, further clinical studies are needed before researchers can draw any conclusions about green tea and lung cancer.

Pancreatic cancer. In one large-scale clinical 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 clinical 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 clinical 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 clinicial study including more than 26,000 men and women in Japan found no association between green tea consumption and stomach cancer risk. Some clinicial studies even suggest that green tea may increase the risk of stomach cancer.

Further clinicial 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.

A few small clinical studies have found that daily supplementation of the diet with green tea-extract powder lowered the hemoglobin A1c level in individuals with borderline diabetes.

Liver disease

Population-based clinical 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

Clinical 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. Some researchers speculate that substances in green tea known as polyphenols, specifically the catechins, are responsible for the herb's fat-burning effect.

Other uses

Drinking green tea has been found effective in a small clinical study for dental caries, or tooth decay. More studies need to be performed. Green tea may also be useful in inflammatory diseases, such as arthritis. Research indicates that green tea may benefit arthritis by reducing inflammation and slowing cartilage breakdown. Chemicals found in green tea may also be effective in treating genital warts and preventing symptoms of colds and influenza.

Plant Description:

Green, black, and oolong tea are all derived from the leaves of the Camellia sinensis plant. Originally cultivated in East Asia, this plant grows as large as a shrub or tree. Today, Camellia sinensis grows throughout Asia and parts of the Middle East and Africa.

People in Asian countries more commonly consume green and oolong tea while black tea is most popular in the United States. Green tea is prepared from unfermented leaves, the leaves of oolong tea are partially fermented, and black tea is fully fermented. The more the leaves are fermented, the lower the polyphenol content (See: "What's It Made Of?") and the higher the caffeine content. Green tea has the highest polyphenol content while black tea has roughly two to three times the caffeine content of green tea.

What's It Made Of?:

The healthful properties of green tea are largely attributed to polyphenols, chemicals with potent antioxidant properties. In fact, the antioxidant effects of polyphenols appear to be greater than vitamin C. The polyphenols in green tea also give it a somewhat bitter flavor.

Polyphenols contained in teas are classified as catechins. Green tea contains six primary catechin compounds: catechin, gallaogatechin, epicatechin, epigallocatechin, epicatechin gallate, and apigallocatechin gallate (also known as EGCG). EGCG is the most studied polyphenol component in green tea and the most active.Green tea also contains alkaloids including caffeine, theobromine, and theophylline. These alkaloids provide green tea's stimulant effects. L-theanine, an amino acid compound found in green tea, has been studied for its calming effects on the nervous system.

Available Forms:

Most green tea dietary supplements are sold as dried leaf tea in capsule form. Standardized extracts of green tea are preferred. There are also liquid extracts made from the leaves and leaf buds. The average cup of green tea contains between 50 - 150 mg polyphenols (antioxidants). Decaffeinated green tea products contain concentrated polyphenols. Caffeine-free supplements are available.

How to Take It:

Pediatric

There are no known scientific reports on the pediatric use of green tea, so it is not recommended for children.

Adult

Depending on the brand, two to three cups of green tea per day (for a total of 240 - 320 mg polyphenols) or 100 - 750 mg per day of standardized green tea extract is recommended. Caffeine-free products are available and recommended.'

Precautions:

The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs contain active substances that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, people should take herbs with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine.

People with heart problems, kidney disorders, stomach ulcers, and psychological disorders (particularly anxiety) should not take green tea. Pregnant and breast-feeding women should also avoid green tea.

People who drink excessive amounts of caffeine (including caffeine from green tea) for prolonged periods of time may experience irritability, insomnia, heart palpitation, and dizziness. Caffeine overdose can cause nausea, vomiting, diarrhea, headaches, and loss of appetite. If you are drinking a lot of tea and start to vomit or have abdominal spasms, you may have caffeine poisoning. Lower your caffeine intake and see your health care provider if your symptoms are severe.

Possible Interactions:

If you are being treated with any of the following medications, you should not drink green tea or take green tea extract without first talking to your health care provider:

Adenosine -- Green tea may inhibit the actions of adenosine, a medication given in the hospital for an irregular (and usually unstable) heart rhythm.

Antibiotics, Beta-lactam -- Green tea may increase the effectiveness of beta-lactam antibiotics by reducing bacterial resistance to treatment.

Benzodiazepines -- Caffeine (including caffeine from green tea) has been shown to reduce the sedative effects of benzodiazepines (medications commonly used to treat anxiety, such as diazepam and lorazepam).

Beta-blockers, Propranolol, and Metoprolol -- Caffeine (including caffeine from green tea) may increase blood pressure in people taking propranolol and metoprolol (medications used to treat high blood pressure and heart disease).

Blood Thinning Medications (Including Aspirin) -- People who take warfarin, a blood thinning medication, should not drink green tea. Since green tea contains vitamin K, it can make warfarin ineffective. Meanwhile, you should not mix green tea and aspirin because they both prevent platelets from clotting. Using the two together may increase your risk of bleeding.

Chemotherapy -- The combination of green tea and chemotherapy medications, specifically doxorubicin and tamoxifen, increased the effectiveness of these medications in laboratory tests. However, these results have not yet been demonstrated in studies on people. On the other hand, there have been reports of both green and black tea extracts stimulating a gene in prostate cancer cells that may cause them 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 for prostate cancer in particular.

Clozapine -- The anti-psychotic effects of the medication clozapine may be reduced if taken fewer than 40 minutes after drinking green tea.

Ephedrine -- When taken together with ephedrine, green tea may cause agitation, tremors, insomnia, and weight loss.

Lithium -- Green tea has been shown to reduce blood levels of lithium (a medication used to treat manic/depression).

Monoamine Oxidase Inhibitors (MAOIs) -- Green tea may cause a severe increase in blood pressure (called a "hypertensive crisis") when taken together with MAOIs, which are used to treat depression. Examples of MAOIs include phenelzine and tranylcypromine.

Oral Contraceptives -- Oral contraceptives can prolong the amount of time caffeine stays in the body and may increase its stimulating effects.

Phenylpropanolamine -- A combination of caffeine (including caffeine from green tea) and phenylpropanolamine (an ingredient used in many over-the-counter and prescription cough and cold medications and weight loss products) can cause mania and a severe increase in blood pressure. The FDA issued a public health advisory in November 2000 to warn people of the risk of bleeding in the brain from use of this medication and has strongly urged all manufacturers of this drug to remove it from the market.

Both Types of Tea – Black and Green-come from the Camellia sinensis plant.Dried leaves harvested from the rapidly growing indian Assamica from the basis of black tea,the most commonly consumed tea in the west.Leaves harvested from the slow- growing Chinese sinensis shrub yields the delicate flavour we know as green tea.The Chinese sinensis plant contains less caffeine than its indian cousin,Indian Assamica.Therefore,green tea has slightly less caffeine than black tea.Buds,shoots,leaves and stems form the basis of most tea blends.

Many people sensitive to Caffeine report that green tea doesn't give them the jitters,shakes and insomnia that black tea,coffee,or cola gives them.Many people report feeling calm after sipping green tea.Why is the effect of Caffeine in green tea different from that of other beverages?

The answer lies in the chemical compositions of the tender young shoots harvested to make high- grade green tea.Two components alter the effects of caffeine in green tea : L-theanine and EGCG.

L-Theanine(theanine), an amino acid found in green tea,promotes feelings of relaxatio discovering that it works with many brain chemicals related to mood, including dopamin that theanine, researchers speculate that the theanine counters the effect of caffeine and takes the edge off those caffeine jitters.

The second component in green tea that alters caffeine effects is EGCG.Thsi miracle compound stimulates the body's immune system in a myraid of ways.Science Daily reports that EGCG may be effective in fighting bacterial sepsis, and often deadly bacterial infection.In addition to its powerful immune system activity, EGCG mitigates the caffeine content in green tea.As you brew a steaming cup of green tea and pour hot water over the tea leaves ,evidence suggests that EGCG binds to caffeine and neutralizes its effects.

There are two ways to lose weight -- either reduce energy intake, or increase energy expenditure. Because hypothyroidism -- even after treatment -- may reduce energy expenditure in some people, patients naturally are looking for options that can help safely help raise the metabolism.In a study reported on in the American Journal of Clinical Nutrition, it was found that green tea extract resulted in a significant increase in energy expenditure (a measure of metabolism), plus also had a significant effect on fat oxidation. While some of the effects were originally theorized to be due to the caffeine content of green tea, the researchers discovered that the tea actually has properties that go beyond those that would be explained by the caffeine. The same amount of caffeine as was in the green tea, administered alone, failed to change energy expenditure in other studies. This led reseachers to believe that there is some interaction going on with the active ingredients of green tea that promotes increased metabolism and fat oxidation.

What can be the Implication to you?

If you were to incorporate green tea into your weight loss efforts, how is the best way to go about it?

One way would be to choose a reputable brand of organic green tea at a health food store or natural grocery, and start by taking a cup of tea every day. You can also take a green tea extract, in the form of a supplement.

Either way, says dietitian Lynn Moss, M.S., R.D., a continuing education specialist for Pharmavite, makers of Nature Made and Nature's Resource supplements and herbs, you should definitely take the green tea with meals, to reproduce the study's conditions as much as possible.

Moss also feels that green tea may be a good choice for thyroid patients because, unlike caffeine, " green tea has the potential to accelerate metabolism -- which can help weight loss slightly -- without overstimulating your adrenal glands."

And even a small effect can go a long way, when you are dealing with a metabolism that may not rebound entirely, despite hypothyroidism treatment.

Is Green Tea Dangerous to Thyroid?

In response to my article, some readers expressed concerns regarding the high fluoride content in tea, and the negative relationship between ingestion of too much fluoride and thyroid problems, as well as other health concerns.

This is definitely something to be considered before deciding to take green tea.

While green tea has some definite benefits in the cancer-prevention and metabolism-boosting arena, the fluoride content may, according to some practitioners, be a concern for the public in general, but specifically for thyroid patients.