Dr Sushil Rudra 

Durgapur Steel City


Is drinking tea harmful?/

Is drinking tea harmful to health? A section of people thinks that the habit of drinking tea is not benefited their health. They advise with ayurvedic literature, let’s see why tea is not a good diet for physical and mental health.

But is it true? Our medical science has changed this old concept. Scientists have been trying to expose so many benefits of drinking tea. Like water, it’s our second liquid element which we drink in everyday life. It’s one of the main drinks that is deeply connected with our lifestyle. So let’s see, what are the benefits of drinking tea.


1. Introduction 2. Types of Tea 3. Green Tea and its compounds 4. Why is green tea so effective? 5. Benefits of drinking tea 6. Tea and Neurological effects 7. Dementia 8. Tea for Stress relieving 9. Obese control and Tea 10. Tea can reduce heart disease 11. Tea can be helpful for diabetes 12. Tea and Hydration 13. Tea enhances immunity 14. Drink tea to avoid the risk of cancer 15. Bottom line: Health risk and tea


  We start the morning with tea and biscuits. Again we drink tea in the afternoon. It’s seen in every household, may it be a village or urban area. The people who are busy in office or school, college or hospital, they’re habituated to drinking tea several times a day. 

Tea, the most popular beverage consumed by two-thirds of the world’s population, is made from the processed leaf of Camellia sinensis. 

       Tea types, based on processing or harvested leaf development are black (fermented), green (non-fermented) and oolong (semi-fermented).

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 These major tea types differ in how tea is produced and processed. The different processes of drying and fermentation determine its chemical composition. 

    Green tea is produced by using young tea leaves and sold for consumption without fermentation after withering, steaming or pan firing, drying and grading.

     With pan firing, it prevents the tea leaves from fermenting by the natural enzyme activities. Tea leaves are allowed to ferment for several hours before being either smoke fired, flame fried or steamed to make black tea. 

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                            Oolong tea is produced by partial oxidation of the leaf, an intermediate between the process for green and black tea [1]. Black tea is made by first exposing the tea leaves to air, causing them to oxidize. 

      This oxidation process turns leaves into a deep brown colour and during this process, the flavour is intensified. The leaves are then left as such or are heated, dried and crushed. 

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Green tea is best studied for its health benefits, including cancer, chemopreventive and chemotherapeutic effects [2, 3]. But emerging data is showing that black tea may possess similar health-promoting attributes.


Green tea contains characteristic polyphenolic compounds, (−)-epigallocatechin-3-gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG) and (−)-epicatechin (EC). Flavonols, including quercetin, kaempferol, and myricetin and their glycosides are also present in tea.

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A typical cup of green tea usually contains 250–350 mg of tea solids, of which 30–42% are catechins and 3–6% caffeine [4].

The major active constituents of tea are catechins, and among them, EGCG is the most potent and much of the anti-carcinogenic effect of green tea is predominantly credited to it.

          Some catechins are oxidized or condensed to theaflavins (theaflavin, theaflavin-3-gallate, theaflavin-3′-gallate and theaflavin-3-3′-gallate) (3–6%) and thearubigins (12–18%) during fermentation of fresh tea leaves. These are responsible for the bitter taste and dark colour of black tea. 

          Black tea contains mainly thearubigins, theaflavins, flavonols and catechins. The total polyphenol content of green and black teas is similar, but with different types of flavonoids present due to the degree of oxidation during processing [5].


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These are as follows: 

It increases metabolism.            Reduces the risk of dementia.

Reduces the risk of heart disease.

Tea can reduce obese

Alleviates stress.

Healthy hydrator.

Soothes colds.

Cuts cancer risk.

Minimize neuro problems and stress. 

So for me, drinking a cup of tea is like getting new energy and life. Whether hot or cold, this beverage brings benefits and comfort for several reasons.

Throughout the day, tea provides a steady presence. In the morning, tea is a trusted companion to my breakfast. It acts as a speed bump to furnish my plethora of work. I don’t feel any lather while I am engaged in my schedule. 

 Even when I get bored, I used to drink a cup of streamy tea. Surprisingly, I can overcome all the tiredness and boredom. 

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As highlighted during the sixth International Scientific Symposium on Tea and Human Health, which took place in April, tea is the second-most consumed beverage in the world after water. With over 159 million Americans drink tea on any given day.

Aside from its comforting aspects, tea offers several health benefits too. The three most popular types of tea consumed worldwide are unfermented green tea, fully fermented black tea and partially fermented oolong tea. These are manufactured from the leaves of the plant Camellia sinensis.  

 However, it’s rich in antioxidants called polyphenols. These teas also contain L-theanine, an amino acid. Int is, for the most part, uniquely found in tea. (Herbal teas do not come from Camellia sinensis, but are an infusion of leaves, roots, bark, seeds or flowers of other plants.)

 Gradually, the consumer of drinking tea is increasing in the world population for its benefits.

Jeffrey Blumberg, an active professor emeritus in the Friedman School of Nutrition Science and Policy at Tufts University in Boston says:

“There is a growing body of research from around the world demonstrating that drinking tea can enhance human health in many ways”.

“True teas – which include black, green, white, oolong and dark – can contribute significantly to the promotion of public health,” he explains. 

“Evidence presented at this symposium reveals results – ranging from suggestive to compelling – about the benefits of tea on cancer, cardiometabolic disease, cognitive performance and immune function.”

Here are some reasons tea should be making a regular appearance on your shopping list.


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Due to a lack of well-controlled clinical trials, the effect of tea on the progression of neurodegenerative disorders has not been studied on a large scale.

 The protective effect of EGCG against neuronal diseases may involve its radical scavenging and iron chelating activity and/or regulation of antioxidant protective enzymes.

      Reduced risk for Parkinson’s disease was observed for more than or equal to 2 cups/day of tea consumption and two or more cola drinks/day.

     The associations for tea and cola drinks were not affected by smoking or coffee consumption [57]. A case-control study was conducted in China to examine the relationship between coffee and tea drinking, cigarette smoking, and other environmental factors and the risk of Parkinson’s disease.

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 There it was found that one unit of coffee and tea (3 cups/day for 10 years) would lead to a 22% and 28% risk reduction, respectively, of Parkinson’s disease demonstrating a dose-dependent protective effect of coffee and tea in an ethnic Chinese population [58].

    The association of coffee and tea consumption with the risk of incident Parkinson’s disease among 29,335 Finnish subjects aged 25 to 74 years without a history of Parkinson’s disease at baseline was investigated. 

        They were followed up for 12.9 years and during this time, 102 men and 98 women developed Parkinson’s disease. 

Therefore, it was noted that subjects who habitually drank  3 cups of tea/day had a reduced risk of incident Parkinson’s disease [59]. 

      In the Singapore Chinese Health Study, a prospective cohort of 63,257 Chinese men and women, all 157 Parkinson’s disease cases were identified. 

So there was an inverse relationship between black tea with Parkinson’s disease risk that was not confounded by total caffeine intake or tobacco smoking, while green tea was unrelated to Parkinson’s disease risk [60].


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                  Drinking tea can help neuro patients. Especially Dementia patients.  Dementia is characterized by the impairment of memory and judgement. It leads to an increased dependence on others. So drinking tea regularly might help them. It seems to benefit from tea – black, green, white and oolong.

    A new study in Translational Psychiatry found that people who drank tea were 16% less likely to develop different forms of dementia when compared with those who did not drink tea.

“The mechanisms of action of tea underlying this benefit are not definitively known, but several experimental studies have indicated tea flavonoids may invoke extensive cellular pathways of antioxidants and activities of neurorescue, which might prevent memory deficits,” explains Blumberg. 

      He also said: “In addition, tea flavonoids have been found to have anti-inflammatory properties, which could slow the progression of cognitive decline.”

Blumberg also notes that tea may play a neuroprotective role in the cognitive decline because it has a positive effect on the flow of blood vessels in the brain

   The study showed that three cups a day produced the strongest protective effect against developing the disease.

                Since there are currently no conclusively effective drug treatments once an individual has developed dementia, prevention is key.

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Evidence has shown that tea from Camellia sinensis seems to have a calming effect, which helps combat stress. Most notably, tea seems to act upon attention and alertness.

“When experiencing elevated stress, tea is an optimal beverage of choice due to its beneficial effects on attention,” says Louise Dye, professor of nutrition and behaviour in the University of Leeds Human Appetite Research Unit, based in the School of Psychology.

Studies suggest that the unique combination of caffeine and the amino acid L-theanine in tea can improve attention, says Blumberg.


Though the jury is still out, some studies suggest that the caffeine and catechins, a type of polyphenol, in tea may help with weight loss.  

      Decaffeinated green teas did not appear to produce the same results. Though the research on caffeinated green tea looks promising. There are still a lot of unanswered questions. Plus, the results have been minimal – only one to two pounds of additional weight loss. 

 But note, that research is lacking to support the wide range of herbal tea products advertised for weight loss and these can be harmful depending on their ingredients.


Drinking tea both green and black is helpful to maintain a sound heart. 

Polyphenols, in particular flavonoids, are found in both green and black tea. So have been suggested to play a primary role in the reduction of cardiovascular disease risk.

Here  CVD includes diseases of the heart and/or blood vessels, such as coronary artery diseases, heart failure, stroke and cardiomyopathy.

Tea should be taken in our regular diet.  A May 2022 review study in the journal Food Science and Wellness showed that daily green or black tea consumption is inversely associated with CVD risks, especially in habitual tea drinkers.


A large population-based study comprising 40,000 middle-aged adults in Japan found that, compared to no tea consumption, habitual tea intake (daily average of two cups or approximately 17 oz. for 10 years) was associated with a reduced risk of death from CVDs. Read more: How Can We Get White Teeth Using the Best Toothpaste?


Though the research relating to drinking tea in diabetes is less clear. Some studies suggest that the catechins in green tea may help to keep blood sugar in check, reducing the risk of developing Type 2 diabetes. 

      However, these findings have mainly been based on practices in other countries and not repeated in clinical trials.

Some findings of the researchers are also evaluating if spearmint and chamomile herbal teas have a role to play in preventing diabetes. More research is needed on the amount of tea and type of tea, especially since some of the results have involved tea in the form of a supplement instead of a drink.


 Drinking tea can have hydration power. It’s better to drink cold tea. 

But whether chilled or hot, tea is an excellent source of hydration.

      The choice of an iced tea naturally sweetened with a splash of fruit juice instead of a sugary beverage could bring big benefits, instead of potentially wreaking havoc on your blood sugar levels.

     You can mix fruit juice in your tea.          Fruits like strawberries or watermelon are used in a pitcher of unsweetened iced tea and kept in the fridge for a refreshing pick-me-up after a workout, or cut an apple or pear into a steamy mug of tea and enjoy a baked fruit when you’re done. Read more:WHY IS MANGO THE KING OF FRUITS?


   I have seen my elder brother who used to drink tea several times a day. Even he used to have handmade bread with tea for dinner. He is now near 80 having no complications in health. 

Therefore, Green tea should be a key component of a healthful food pattern as it may help support your immune system and increase your body’s resistance to illnesses. 

My inference gets support when Dayong Wu, associate director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston says : 

       “Tea helps your body ward off infection and, in the event, you do become sick, it will help your body respond to illness more efficiently by ridding itself of the infection.”

     The scientists suspected that antioxidants called catechins, which are particularly abundant in unfermented green tea, help fight against a variety of pathogens by improving the way the immune system responds.

        As a result, tea may also help immunity and help fight colds and viruses. In addition, a stuffy nose can be unclogged by breathing in the warm vapours that arise from a sweltering cup of tea. Warm liquids, in general, help assuage congestion.


It’s suspected that antioxidants called catechins, which are particularly abundant in unfermented green tea, help fight against a variety of pathogens by improving the way the immune system responds. 

     As a result, tea may also help immunity and help fight colds and viruses. In addition, a stuffy nose can be unclogged by breathing in the warm vapours that arise from a sweltering cup of tea. Warm liquids, in general, help assuage congestion.


Believe it or not, Tea can protect you from cancer.  Powerful compounds called flavonoids to protect against damage caused by free radicals, helping cut the risk of cancer.

     “There is strong evidence that some polyphenols have cancer-preventing properties. These are beneficial in fighting cancer, such as antioxidants and anti-inflammation,”

– says Raul Zamora-Ros, a principal investigator at the Unit of Nutrition and Cancer at the Bellvitge Biomedical Research Institute in Barcelona.

Although more research needs to be done to determine the optimal dose and duration of tea consumption, it seems that higher intakes of tea consumption may reduce the risk of some forms of cancer.


        It’s investigated among many dietary agents for chemopreventive properties against prostate cancer (PCa), green tea and its constituent polyphenols (GTP) have received much attention. 


      A Phase II trial was conducted in patients with androgen-independent prostate carcinoma to investigate the antineoplastic effects of green tea. 


      Forty-two patients asymptomatic who had manifested, progressive prostate-specific antigen (PSA) elevation with hormone therapy were evaluated.

           Six grams of green tea per day orally in 6 divided doses were given to patients and each dose contained 100 calories and 46 mg of caffeine. A decline in more than or equal to 50% in the baseline PSA value occurred in a single patient and it was not continued beyond 2 months. 

       The median change in the PSA value increased by 43% at the end of the first month. Grade 1 or 2 green tea toxicity occurred in 69% of patients, along with Grade 3 toxicity and one episode of Grade 4 toxicity [19]. 


    In Hangzhou, southeast China, a case-control study was conducted on 130 incident patients with histologically confirmed adenocarcinoma of the prostate. The risk of PCa declined with increasing frequency, duration and quantity of green tea consumption and there were significant dose-response relationships, suggesting preventive effects of green tea [20].


            The efficacy of green tea capsules was tested on patients with hormone-refractory prostate cancer (HRPCa) by Choan et al. [21]. 

     The efficacy of green tea, prescribed as an alternative complementary formulation was tested on HRPCa. PSA was the primary endpoint and estimated after a minimum of 2 months of therapy.

     As a result,  It was found that 12 patients reported at least one side effect among 19 patients enrolled in the study. The minimum 2 months of therapy was not completed by 4 patients and 15 patients completed at least 2 months of therapy. 

            Within 2 months of starting therapy, progressive disease was noted in 9 of these patients and 6 patients developed it after adding 1 to 4 months of therapy. 

      Therefore, based on the results of this study, it was concluded that green tea had minimal clinical activity against HRPCa [21].

            In high-grade prostate intraepithelial neoplasia volunteers, a clinical trial was conducted to assess the safety and efficacy of green tea catechins for the chemoprevention of PCa.

        Daily treatment consisted of three green tea catechins capsules of 200 mg each. Only one tumour was diagnosed among the 30 green tea catechins-treated men with an incidence of 3%.

         On the other hand,  nine cancers were found among the 30 placebo-treated men with an incidence of 30% after 1 year. There was no significant change in total PSA between the two arms, but the green tea catechism 

         Furthermore, the scientists used daily treatment consisting of three green tea catechins capsules of 200 mg each. Only one tumour was diagnosed among the 30 green tea catechins-treated men with an incidence of 3%. 

         On the other hand,  nine cancers were found among the 30 placebo-treated men with an incidence of 30% after 1 year. There was no significant change in total PSA between the two arms, but green tea catechins-treated men showed values constantly lower than placebo-treated ones. 

There were no reports of significant side effects and administration of green tea catechins also reduced lower urinary tract symptoms [22]. 

    There is another survey. Green tea consumption habits of 49,920 men aged 40–69 years were investigated in the Japan Public Health Center-based prospective study. During that time, 404 men were newly diagnosed with PCa, of which 114 had advanced cases, 271 were localized, and 19 were of an undetermined stage.

    It was established that localized PCa was not affected by the consumption of green tea, there was a dose-dependent decrease in the risk of advanced PCa by intake of green tea [23].

         It has been reported that there was a significant reduction in serum levels of PSA, hepatocyte growth factor and vascular endothelial growth factor in men with prostate cancer after brief treatment with green tea extract containing EGCG (Polyphenon E), with no elevation of liver enzymes [24]. 

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    Tea drinking was associated with a reduced risk of lung cancer in male cigarette smokers in a case-control study in Uruguay [26]. 

           In a population-based case-control study in Shanghai, China, consumption of green tea was associated with a reduced risk of lung cancer among non-smoking women and the risk decreased with increasing consumption [27]. 

      There was a significant decrease in urinary 8-hydroxydeoxyguanosine after drinking decaffeinated green tea among smokers over 4 months in a randomized controlled tea intervention phase II trial [28]. 

        The maximum tolerated dose of green tea extract (GTE) in patients with advanced lung cancer was determined by Laurie et al. 

             There was a higher risk of lung cancer in smokers who never drank green tea, as compared to smokers who drank green tea >1 cup/day [31].


Breast cancer is now an epidemic. So many demonstrations are going on. In the meantime, epidemiological studies have demonstrated inconsistent results on the relation between green tea intake and the risk of breast cancer.

    Stages I and II breast cancer patients showed a lower recurrence rate and a longer disease-free period when consuming more than 5 cups of green tea/day compared to those consuming less than 4 cups/day [32]. 

                   A significant inverse relationship between intake of green tea and risk of breast cancer was reported in a case-control study conducted among Asian-American women in Los Angeles County.

 Almost  13 studies were examined and data on the consumption of either green tea or black tea, or both about breast cancer risk was provided [33]. 

      The combined results from the four studies indicated a reduced risk of breast cancer for highest versus non/lowest intake of green tea. Contradictory results were observed in case-control as compared to cohort studies for black tea. 


Is drinking tea harmful? This concept is not right. Tea consumption has been reported to have beneficial effects on several types of cancers. Consumption of green tea was associated with a lower risk of oesophageal cancer in a case-control study of oesophageal cancer patients in Shanghai [38]. 

         Individuals who consumed more than 10 cups of green tea/day showed a remarkable reduction of relative risk for lung, colon, and liver cancers [39].

      In a study, we see that consumption of black tea reduces colon cancer risk in both men and women [40].

    Regular green tea consumption at least three times/week for more than six consecutive months was related to a reduced risk of colorectal cancer in non-smokers and the risk decreased with the increased amount of green tea consumption. *See Benefits of Coconut Water

Each 2 g rise of intake of dry green tea leaves/day was associated with a 12% reduction in the risk of colorectal cancer. 

     However, there was no significant association between green tea consumption with the risk of colorectal cancer among smokers. It’s suggesting that regular consumption of green tea may reduce colorectal cancer risk among non-smokers [41].

       It was concluded that green tea consumption was associated with a moderate reduction in risk for primary liver cancer [42]. 

      The association between green tea drinking and the risk of pancreatic cancer was investigated in a population-based case-control study in urban Shanghai with the recruitment of 908 patients with pancreatic cancer and 1067 healthy controls.

 It was found that regular green tea drinking was associated with a 32% reduction in pancreatic cancer risk as compared to those who did not drink tea regularly in women. 

Various studies proved that tea may affect glucose metabolism and insulin signalling. So it’s causing interest in the health effects of tea consumption on diabetes.

  Consuming more than or equal to 4 cups/day of tea had a 30% lower risk of developing type 2 diabetes than did those who did not consume tea [51]. 

 Adults who consumed more than or equal to 6 cups/day of green tea lowered their risk of diabetes by 33%. Even no association with diabetes risk was found for oolong or black teas. 

      Consumption of more than or equal to 3 cups/day of coffee lowered the risk of diabetes by 42% and high caffeine intake can reduce the risk of diabetes 33%.

A lowered diabetes risk was also observed in women after green tea and caffeine consumption [52].

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Another investigation shows that decaffeinated coffee was at increased risk of rheumatoid arthritis. In contrast, women consuming more than or equal to 3 cups/day of tea displayed a decreased risk of rheumatoid arthritis compared with women who never drank tea.


Last but not least. Drink tea when you feel fatigued.  Tea is the most widely consumed beverage in the world, next only to water. 

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Though there are lots of good things about consuming tea, overdoing it can put your health at risk.

One risk is caffeine overload. Large amounts of caffeine may lead to nervousness, and restlessness and may disturb your sleep. 

           Some people may also experience loose stools and other gastrointestinal issues. Nausea, abdominal pain, heartburn, dizziness and muscle pain are also possible side effects of consuming too much caffeine.  

     It may also interact with certain medications and increase the effects of caffeine in the body. The total daily intake of caffeine from all sources should not exceed 400 milligrams.*

Reference :

  • Wikipedia

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