We’ve heard that tea leaves steeped in boiling water are used by people to keep them healthy and physically fit. As science developed, people began to examine the advantages and disadvantages of drinking tea scientifically.
All the three varieties of tea viz., green, black, and oolong are prepared from the same tree but difference is in the processing. Green tea is prepared from unfermented leaves and contains the highest concentration of powerful antioxidants called polyphenols. Antioxidants in green tea can neutralize free radicals and may reduce or even help prevent some of the damages caused by free radicles such as development of aging process besides several health problems such as heart diseases and cancer. A recent report published in online version of obesity suggested that green tea consumption slow downs the weight gain as Epigallocatechin-3-gallate (EGCG) – a compound found in most green teas, reduced the ability to absorb fat and enhanced ability to use it.
Claims regarding health benefits of green tea:
1. It is claimed that green tea prevents atherosclerosis, particularly coronary artery disease.
-However, The U.S. Food and Drug Administration (FDA) didn’t allow tea makers to use labels to claim that green tea reduces the risk of heart disease in absence of any credible evidence.
2. It is claimed that green tea lowers total cholesterol and raises HDL cholesterol.
– that that men who drink green tea may have lower total cholesterol than those who do not drink green tea.
– that polyphenols in green tea may block the intestinal absorption of cholesterol and promote its excretion from the body as observed in clinical trials on animals..
– that green tea significantly reduced blood levels of harmful LDL cholesterol in smokers.
3. It is claimed that green tea helps protect against cancer
-This claim is based on the facts that cancer rates tend to be low in countries where people regularly consume green tea. However, there are no evidences to suggest that green tea is solely responsible for this less rate.
-Research suggests that the polyphenols in green tea may play some role in the prevention of cancer.
– benefits of polyphenols of green tea are indicated either in terms of less spread of cancer or in terms of prolonged survival period of patients.
– Benefits of green tea are indicated in bladder, ovarian, prostrate , and breast cancer.
– In case of colon, esophageal, lung and pancreatic cancer, results are inconclusive and further research is needed to advocate use of green tea for prevention or other related benefits in such cases.
-Although laboratory studies suggest that green tea helped in reducing the risk of prostrate cancer, it stimulated the genes that cause cells to be less sensitive to chemotherapy drugs. Hence, people receiving chemotherapy drugs should not drink green tea.
-epigallocatechin gallate (EGCG) is the main polyphenol in green tea that have anti-inflammatory and anti-cancer properties.
– Studies on relationship between stomach cancer and use of green tea showed contradictory results. In few studies it had inhibitory effects, in other studies no relationship could be established while in some studies green tea increased the risk of stomach cancer. Hence, further studies are needed.
4. It is claimed that green tea prevents the development of type 1 diabetes
– green tea may help prevent the development of type 1 diabetes and slow the progression of disease if already developed. However, this study was conducted with animals.
– Green tea may help regulate glucose in the body.
– in few studies, it was found that daily supplementation of the diet with green tea-extract powder lowered the hemoglobin A1c level in individuals with borderline diabetes.
5. It is claimed that consumption of green tea provides protection against liver disease
– Clinic survey shows that there are less chances of developing liver disorders in men who drink more than 10 cups of green tea per day.
– green tea is believed to protect the liver from the damaging effects of toxic substances such as alcohol.
– In mice, green tea helps protect against the development of liver tumors.
– Results suggest that catechin, a polyphenol present in green tea, may help treat viral hepatitis as observed with catechin isolated from green tea and used in very high concentrations. However the same polyphenol is never present in such high quantities in green tea as used in the study.
6. It is advocated that gren tea helps in weight loss in moderately obese individuals
– Research suggests that the combination of green tea and caffeine helped in losing weight
– catechins, are considered responsible for the fat-burning effect of green tea.
7. It is claimed that green tea extract is effective in treating genital warts, arthritis and dental decay
– few clinical studies supports these beliefs that green tea may help in treating genital warts, reducing the inflammation in arthritis and effective in treating tooth decay.
Side effects/ credible evidences:
– Dry green tea contains substantial amounts of caffeine which can cause nausea, insomnia, or frequent urination.
– FDA found very limited credible evidence for qualified health claims specifically for green tea and breast cancer and for green tea and prostate cancer.
– Similarly, FDA found 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 Cardiovascular diseases.
– However, FDA approved Kunecatechins ointment (based on green tea) which is is indicated for the topical treatment of external genital and perianal warts.
Precautions/Interactions with other drugs:
Although green tea may be useful in prevention of some diseases, trials have shown that chemicals present in green tea may interact with few other drugs. Hence, people using these drugs should avoid the use of green tea especially when they are using these drugs.
1. Consumption of green tea, concentrated green tea extract, and other green tea products (such as EGCG capsules) be avoided for patients undergoing bortezomib treatment.
2. If green tea is consumed empty stomach, there may be chances of liver damage as observed in some research studies.
3. People detected with heart problems, kidney disorders, stomach ulcers, and psychological disorders should avoid green tea.
4. It’s safe for pregnant and breast-feeding women to avoid the consumption of green tea .
5. It may inhibit the actions of adenosine, increase the effectiveness of beta-lactam antibiotics, reduce the sedative effects of diazepam and lorazepam, and use with aspirin may increase the risk of bleeding.
6. People should avoid green tea intake if they are receiving chemotherapy for prostrate cancer.
7. Consumption of green tea may prolong the effect of oral contraceptives
8. There are several other drugs which may interact with chemicals present in green tea.
On the basis of the above facts it may be concluded that detailed studies are required to validate the claims made for positive effects of green tea and people should be aware of its interactions with other drugs.