What are the benefits and harms of green tea?

An overview of green tea

The original home of green tea, also known as Chinese green tea, goes back to China and India. It has been used for many centuries and has gained wide popularity at the present time. Tea of all kinds is one of the most consumed drinks around the world after water, and all types of tea are prepared except herbal tea From the leaves of the Camellia sinensis plant, and the type of tea is determined according to the level of oxidation to which the leaves have been exposed. It is worth noting that green tea is made from non-oxidized tea leaves, and it is one of the types of tea that is less subjected to various processing processes, and it also contains higher levels of antioxidants compared to tea. the black.

Benefits of green tea

The benefits of green tea according to the degree of effectiveness

Possibly Effective

Reducing the risk of heart disease: A study published in the International Journal of Cardiology in 2016 indicated that green tea can help reduce cholesterol levels, diastolic blood pressure, and the risk of hyperlipidemia in males with coronary heart disease, in addition to a link Reverse between the risk of developing coronary artery disease and frequent consumption of green tea in males without heart disease, and consumption of 3 cups per day of green tea can significantly reduce the risk of females developing coronary artery disease.
Reducing the risk of endometrial cancer: A systematic review and meta-analysis of several studies, published in the Journal of Gynecologic Oncology in 2016, indicated the possibility of an association between drinking green tea and a reduced risk of endometrial cancer, and the analysis indicated that more studies are needed to reach a conclusion. Clear, and accurately specifying the reasons for this association.
Contribute to lowering blood cholesterol levels: A comprehensive analysis of 14 studies, published in The American Journal of Clinical Nutrition in 2011, indicated that drinking green tea or its extract led to a significant and significant decrease in cholesterol levels, and LDL cholesterol in the blood, without affecting good cholesterol levels.
Helps lower blood pressure: A systematic review published in the Journal of Hypertension in 2015 included 14 studies; It indicated that the consumption of green tea or its extract led to a significant decrease in blood pressure in adults with overweight and obesity, and it indicated the need for more high-quality studies, with more numbers of participants, to confirm the effectiveness of green tea in blood pressure, and it should be noted that it is possible Caffeine in green tea may raise blood pressure in people with high blood pressure, but this effect may be less in people who regularly consume caffeine from green tea and other sources.
Reducing the risk of ovarian cancer: A systematic review of 22 studies published in the Journal of Gynecologic Oncology in 2012 indicated a positive effect of green tea and its components in improving ovarian cancer in laboratory studies and indicated that drinking green tea may reduce the risk of developing ovarian cancer. with ovarian cancer.
The possibility of reducing the risk of developing Parkinson's disease: Parkinson's disease is the second most common neurodegenerative disorder around the world, and a review published in CNS & Neurological Disorders - Drug Targets in 2016 indicated that the phenolic compounds found in green tea, which have antioxidant properties and effects Good for nerves, may help reduce the risk of Parkinson's disease.

There is not enough evidence of its effectiveness

Reducing the risk of amyloidosis: It is a rare disease that occurs when an abnormal protein called amyloid accumulates in the body’s organs and affects their normal functions. A study published in Clinical Research in Cardiology in 2012 indicated an inhibitory effect of green tea and its extract on the development of amyloid heart, but more studies are needed to confirm this efficacy.
Enhancing athletic performance: Scientific evidence about the effect of green tea on athletic performance is conflicting, as some preliminary research indicates that consuming green tea extract as a drink does not improve breathing and athletic performance in people undergoing endurance exercises, while other preliminary research indicates that taking the tablets containing Components of green tea taken three times daily with meals improved some tests of breathing during exercise in healthy adults.
Reducing the risk of bladder cancer: A review published in Medicines in 2018 indicated that evidence about the effect of green tea on bladder cancer is conflicting. Some laboratory and animal studies indicated that phenolic compounds in green tea can inhibit the proliferation and spread of cancer cells in the bladder. While some human studies indicated that there is no significant relationship between green tea consumption and the risk of bladder cancer, there is a need for clearer and broader studies to confirm the anti-cancer effect of green tea.
The possibility of reducing the risk of breast cancer: The results of a study published in the Journal of Molecular Nutrition & Food Research in 2011 showed that despite the availability of evidence about the protective properties of green tea in animal studies, its effect in humans is not clear, due to the relatively small number From human studies, the results of these studies are contradictory, and the mechanisms by which green tea consumption affects the risk of breast cancer in humans are not yet well studied.
Reducing the risk of cervical cancer: A laboratory study published in the International Journal of Gynecological Cancer in 2010 indicated that the polyphenolic compounds in green tea possess properties that inhibit the growth of cancer cells in the cervix, by inhibiting the growth of cervical cells associated with HIV. Human papilloma is closely associated with more than 95% of cervical cancer cases.
Possibility of relieving the common cold: A study published in the Journal of the American College of Nutrition in 2007 indicated that green tea dietary supplements in a specific formulation are safe to use and useful in relieving cold symptoms, in addition to enhancing the functions of gamma-delta-T immune cells in healthy adults.
Reducing symptoms of depression: A study published in The American Journal of Clinical Nutrition in 2009 indicated an association between frequent green tea consumption and a lower prevalence of depressive symptoms in the elderly.
The possibility of reducing the risk of esophageal cancer: A meta-analysis of 10 studies published in BMC Gastroenterology in 2012 indicated that there was no significant association between green tea consumption and the risk of esophageal cancer for people who did not drink alcohol, but an effect of green tea was observed in reducing the risk of cancer. esophagus in females and more studies are needed to confirm the effect of routine consumption of green tea in reducing the risk of esophageal cancer.
Possibility of reducing the risk of bone fractures: A review published in Nutrition Research in 2009 indicated that green tea and its bioactive components may reduce the risk of bone fractures by improving bone mineral density and stimulating the activity of osteoblast cells. and inhibition of osteoclasts.
Reducing the risk of type 2 diabetes: A preliminary study published in the Annals of Internal Medicine in 2006 indicated that green tea and caffeine consumption was associated with a reduced risk of type 2 diabetes, and these results were more evident in women and overweight men. Caffeine consumption was associated with a 33% reduced risk of developing diabetes.
The possibility of reducing influenza infection: A study published in The Journal of Nutrition in 2011 indicated that consuming green tea daily could reduce the risk of children developing influenza infection, but more clinical studies are needed to confirm this effect and evaluate the safety of tea consumption. green by children.
Alleviating seasonal allergic rhinitis: A study published in Allergology International in 2014 indicated that some compounds in green tea can relieve seasonal allergic rhinitis symptoms, but more studies are needed to prove its effectiveness accurately.
Reducing the risk of leukemia: A study published in Cancer Causes & Control in 2009 indicated that consuming green tea, which contains high amounts of catechins, may reduce the risk of leukemia in people between the ages of 16 to 29 years. While no significant effect was seen in the younger age groups.
Reducing the risk of liver disease: A meta-analysis published in the International Journal of Clinical and Experimental Medicine in 2015 indicated that drinking green tea can reduce the risk of developing liver diseases, including hepatocellular carcinoma, hepatitis, hepatic steatosis, and cirrhosis. liver, and chronic liver disease, but more studies are needed to comprehensively evaluate the long-term benefits of green tea.
Reducing the risk of lung cancer: A meta-analysis of 22 studies published in Lung Cancer in 2009 indicated that increased green tea consumption may be associated with an 18% reduced risk of lung cancer.
Enhance alertness and focus: A review of 49 studies published in the Journal of Current Pharmaceutical Design in 2017 indicated that the two compounds theanine and caffeine in green tea have a beneficial effect on sustained attention, and memory, and reduce distraction, and theanine helps with relaxation. By reducing alertness caused by caffeine.
Contribute to maintaining liver health: A study published in the International Journal of Molecular Medicine in 2013 indicated that consuming 700 milliliters per day of green tea, which contains more than 1 gram of catechin compound, for 12 weeks, improved liver fat levels, and reduced inflammation. by reducing oxidative stress in patients with nonalcoholic fatty liver disease.
Reducing the risk of developing non-Hodgkin's lymphoma: also known as lymphoma, cancer that begins with white blood cells called lymphocytes that are an important part of the body's immune system. A comprehensive analysis of a number of studies published in Nutrition and Cancer in 2019 indicated that increased consumption of Green tea may be associated with a reduced risk of developing non-Hodgkin lymphoma.
Reducing the risk of oral cancer: A preliminary study published in the Journal of General Dentistry in 2002 indicated that regular consumption of green tea could be beneficial in reducing the risk of oral cancer, and this may be due to the polyphenols present in green tea, which can stimulate Oral cancer cell programmed death.
Reducing the risk of pancreatic cancer: A study published in Cancer Epidemiology in 2012 indicated that increasing green tea drinking on a regular basis is associated with a 32% reduction in the risk of pancreatic cancer in women, and a decrease in tea temperature is also associated with a reduced risk of pancreatic cancer in women. Both men and women, depending on the amount of tea consumed, and the time spent drinking tea.
Reducing the risk of death from pneumonia: Pneumonia is defined as swelling and inflammation of the tissues of one or both lungs, which usually occurs as a result of a bacterial infection. A preliminary study published in The American Journal of Clinical Nutrition in 2009 indicated that increased tea consumption Green is associated with a lower risk of dying from pneumonia in Japanese women.
Reducing the risk of prostate cancer: A systematic review and meta-analysis published in the Journal of Medicine in 2017 indicated that increased green tea consumption reduced the risk of prostate cancer, and the catechin compound in green tea showed a beneficial effect in reducing the risk of developing this disease. More studies are needed to prove this effectiveness.
Reducing stress: A preliminary study published in the Biological and Pharmaceutical Bulletin in 2017 indicated that low-caffeine green tea consumption can reduce the body's response to excessive stress and tension in students.
Reducing the risk of stroke: A study published in The Tohoku Journal of Experimental Medicine indicated that the incidence of stroke and cerebral hemorrhage during 4 years of follow-up was two or more times higher among people who consumed green tea daily in small amounts, compared to people Who green tea daily in larger quantities.
Other benefits: It is believed that tea may be beneficial in some other cases, but there is not enough evidence to confirm its effectiveness in this, and we mention the following from these cases:

Improvement of infertility, or the inability to conceive within a year of trying to conceive.
Improve the condition of white smear, which appears in the form of white spots inside the mouth, and usually appears as a result of smoking.

Green tea's nutritional value

The following table shows the nutrients found in 100 milliliters of unsweetened green tea:

Nutrient	Food intake
Water	99.88 milliliters
Calories	0 calories
phosphorus	26 milligrams
Potassium	19 milligrams
Calcium	1 milligram
Sodium	7 milligrams
Copper	0.005 milligram
Zinc	0.01 milligram
Caffeine	12 milligrams

Benefits of green tea for weight loss

A systematic review of a number of studies published in the Cochrane database of systematic reviews in 2012 indicated that the results of these studies on the effect of green tea in reducing weight are different, but it was noted that green tea can contribute to unnoticed weight loss in people who suffer from From weight gain or obesity, and it does not have a noticeable effect in maintaining the lost weight.

Green tea damage

Green tea safety

Drinking green tea is often considered safe for most healthy adults when consumed in moderate amounts, and it is likely that green tea extract is safe for most people for a period of up to two years, but this extract can cause stomach upset and constipation in some people, as it may It causes some problems in the liver and kidneys in rare cases.

It is likely that it is not safe to drink green tea for long periods or in high doses. Due to the caffeine content of green tea, drinking it in large quantities may cause some side effects that range in severity from mild to serious, including headache, nervousness, sleep problems, vomiting, and diarrhea. , irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Green tea also contains a chemical compound linked to liver injury when consumed in high doses.

As for children, it is likely that they will be safe to drink green tea in the quantities used in food and beverages, but there is not enough information about the safety of consuming green tea extract for children, and cases of liver damage have been reported in adults who used green tea extract, so some experts recommend avoiding taking the extract. Green tea for children under the age of 18.

It is likely safe to drink green tea during pregnancy, in quantities of up to 6 cups per day, which contain approximately 300 milligrams of caffeine, but it is likely that it is not safe to consume more than 300 milligrams of caffeine during pregnancy, as this has been linked to an increased risk of miscarriage. And many negative effects, green tea may also increase the risk of fetuses developing birth defects associated with folic acid deficiency.

It is worth noting that caffeine passes through the body to reach breast milk, and it can affect the infant, so the breastfeeding mother must monitor her caffeine consumption to ensure that she does not exceed the consumption of two to three cups per day from caffeine sources, as it can lead to the consumption of caffeine by a nursing mother in large quantities. This leads to sleep problems, irritability, and increased bowel activity.

Precautions for the use of green tea

Some groups should be careful when consuming green tea, as it may have side effects that may affect them negatively. Among these groups, we mention the following:

People with anemia: Drinking green tea can make anemia worse.
People with bleeding disorders: The caffeine in green tea can increase the risk of bleeding, so people with bleeding disorders should avoid drinking green tea.
People with heart problems: The caffeine in green tea can cause an irregular heartbeat.
People with diabetes: The caffeine in green tea can affect the control of blood sugar levels, so people with diabetes who drink green tea are advised to monitor their blood sugar levels carefully.
People with glaucoma: or as it is known glaucoma, drinking green tea can increase intraocular pressure, and this increase occurs within 30 minutes of drinking green tea and lasts for at least 90 minutes.
People with high blood pressure: The caffeine in green tea can increase blood pressure in people with high blood pressure. However, this effect does not seem to occur in people who drink green tea or other caffeinated beverages on a regular basis.
People suffering from Irritable Bowel Syndrome: The caffeine in green tea, especially when consumed in large quantities, can exacerbate diarrhea and Irritable Bowel Syndrome symptoms.
People with liver disease: Green tea extract supplements are associated with several cases of liver damage, so it is possible that green tea extracts may worsen the condition of people with liver disease.
People with osteoporosis: Drinking green tea can increase the amount of calcium flowing through the urine, so caffeine consumption should be limited to less than 300 milligrams per day, equivalent to two to 3 cups of green tea, and part of the lost calcium caused by it can be compensated. Avoid caffeine by taking calcium supplements.
People with anxiety: Consuming a large amount of caffeine can cause increased feelings of anxiety, in addition to affecting sleep, and causing upset stomachs and headaches in some people.

Drug interactions of green tea

Some drugs can interact with green tea, causing some health problems, and these drugs include the following:

Quinolone antibiotics: Some antibiotics can reduce the body's rate of breakdown of caffeine, so taking these antibiotics with green tea can increase the risk of side effects of green tea, such as tremors, headaches, and increased heart rate, and among these Medications: ciprofloxacin and enoxacin.
Birth control pills: Birth control pills can decrease how quickly the body breaks down caffeine, so taking green tea with birth control pills can increase the risk of green tea side effects.
Estrogen: Estrogen can decrease how quickly the body breaks down caffeine and taking estrogen pills while drinking green tea can cause an increased risk of green tea side effects.
Asthma medications: Caffeine can stimulate the heart, and asthma medications or beta-adrenergic stimulants can also stimulate the heart, so taking caffeine with some of these medications may cause excessive heart stimulation and heart problems, such as albuterol and metaproterenol.
Depression medications: Green tea can stimulate the body, and some depression medications can also stimulate the body, so consuming green tea with some of these medications may increase the risk of side effects green tea, including phenelzine and tranylcypromine.
Medicines toxic to the liver: These are medicines that can harm the liver, as taking green tea extracts with these medicines can increase the risk of liver damage, so you should avoid taking green tea extracts if taking this type of medicine, and examples of them: acetaminophen, and amiodarone.
Blood-thinning medications: Green tea can slow blood clotting, so taking it with anticoagulant medications may increase the risk of bruising and bleeding, including aspirin, warfarin, and ibuprofen.
Some cancer medications: Green tea may reduce the effectiveness of some medications used to treat cancer, so it is advised to avoid taking green tea products with these medications, including bortezomib.
Nicotine: Stimulant drugs such as nicotine cause stimulation of the nervous system, which can cause tension and an increased heart rate. Caffeine in green tea can cause this effect, so drinking green tea with drugs that stimulate the nervous system may cause serious health problems, in addition to the Increased risk of green tea side effects.
Pentobarbital: The stimulant effects of the caffeine in green tea can block the drug's sleep-inducing effects.
Diabetes medications: There is conflicting evidence about the effect of caffeine on increasing or decreasing blood sugar, and taking some diabetes medications with caffeine can cause a decrease in the effectiveness of these medications. Therefore, it is recommended to monitor blood sugar levels, and there may be a need to change the dose of diabetes medication under the supervision of a doctor. These medications: are insulin and glimepiride.

The right time to drink green tea

Some of the compounds in green tea can affect the absorption of iron and other minerals, so it is recommended to drink it between meals, and consuming caffeine sources before bed can cause sleep disturbances, so it is advised to avoid it.

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What are the benefits and harms of green tea