Green Tea Benefits and Side Effects

Green Tea Benefits and Side Effects

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Green tea is one of the most famous beverages ever created for over health and well-being. It possesses a host of benefits and relatively few side effects.


Green Tea Benefits:


  • Green tea boosts mental acuity and reliefs symptoms of depression
  • Green tea is a mental relaxant
  • Green tea helps to prevent the onset of anger
  • Green tea helps to reduce cholesterol levels
  • Green tea reduces blood pressure levels
  • Green helps with weight loss
  • Green tea prevents and helps to treat diabetes
  • Green tea is a good detoxifier


Wow, what a range of benefits, and more could be included, green tea really is a great healing agent.

Let’s take a closer look at the benefits of green tea.


Mental health

L-Theanine (a key compound found in green tea) has been noted in a study on mental acuity, that after the participants imbibed 97mg of L-Theanine, combined with 40mg of caffeine, demonstrated a significant improvement in mental acuity tests. 1

In another study on brainwaves, they noted that within 40 minutes of imbibing L-Theanine, that the participants demonstrated a noticeable increase in brain wave patterns, associated with deep states of relaxation. 2

In another study, on green tea and its effects on depression, the academics focused on a group of 1058 old aged peoples, who were living in a community for the elderly and who were expressing depressive tendencies. Out if this group, a whopping 44% demonstrated a noticeable decrease in depressive symotoms! 3

This is a truly amazing result, regarding the reduction in depressive symptoms, although do bear in mind that often a massive reduction, in depressive symptoms, in the elderly will more than likely not trickle down to the same result in younger people. In general green tea gets a favourable yet mixed report regarding its anti-depressive qualities. Possible the very significant effect, seen in this study has been brought about both by a relief from a state of health deficiency in the elderly, combined with a large placebo effect, as many elderly people suffer depressive symptoms, because of feeling of relegation. So having a team of researchers testing them, may well have produced a large feel good factor. Which could go some way to influencing the result! Nevertheless such a big study group (1058), demonstrating such improvement certainly suggests a potentially good anti-depressive result!

So from a mental health point of view, a an increase in mental acuity, a reduction in depressive symptoms and an increase in feeling feelings of relaxation, represent some great green tea benefits which relate to our mental health states.


Physical Green Tea Benefits


The physical benefits of green tea are no less startling. In another Japanese based study, on 8552 test subjects, they noted a reduction in the onset of cancer and an overall improvement in cholesterol levels in their participants. 4 In yet another study they noted a 5% drop, in both diastolic and systolic blood pressure levels, in subjects who drank either green or black tea consistently over a 12 week period. 5

Green tea boosts not only the cardiovascular system, but also it helps to prevent the onset of diabetes, and possible it may even improve diabetic symptoms for some diabetic patients, in some cases. In a 2008 study, on diabetic mice, they noted a reduction in fatty liver syndrome, metabolic syndrome and obesity. 6 Fatty liver, is associated with diabetic symptoms, while metabolic syndrome is an indicator of potential cardiac health problems. Admittedly this study was carried out on mice, but more than likely the effect will be similar in human beings. So a potential reduction in diabetes, cardiac disease and potential weight loss too!

On the subject of weight loss, green tea is high in polyphenol components, namely epicatechin, epicatechin gal late, epigallocatechin, and epigallocatechin gallant, which have a thermogenic effect. Also, it is high in catechins, which once again are thermogenic, and of course green tea also contains some caffeine, which once again is thermogenic. All of these factors mean that when green tea is consumed, in significant amounts that it result in thermogenesis (fat burning). 7 In one study they gave the participants 625mg of green tea catechins, mixed with 39mg of caffeine, and noted astonishing that the green tea group lost abdominal fat (post exercise) and also demonstrated a noticeable reduction in morning levels of triglycerides (bad cholesterol), when compared with the control group! 8

Finally, green tea is most famous for its detoxifying effects. Green tea increases antioxidant and enzyme phase II production in the body. 9 Antioxidants fight cell damage and increased enzyme production helps to break down foods, thus providing from nutritional absorption, which in turn boosts the immunity and energy levels, within the body. Furthermore green tea possesses antibacterial and antimicrobial properties, which help to boost the immune system and fight potential disease. 10


Discussion on the Green Tea Benefits

The benefits of green tea are genuine and cannot be argued with; just take a look below this article at the footnote section. This isn’t the usual generic information, on an online magazine, stating that green tea is great; no it’s a bunch of scientists, hard headed down to earth types, who have noted the amazing properties of green tea!

So behind the research what can we generally summarise has been the overall benefits of  taking green tea?

Well green tea possesses serious mental and physiological benefits. It will boost your immune system, reduce the possibility of developing cancerous growths, reduce the potential onset of diabetes and heart disease; all while helping you to lose weight and having a sharper happier mind set at the same time!

If I were to create a health pill which could all of these things, it would be hailed as the next great thing, and it would selling of off the shelf’s faster than the health food shop could replace them!

It for some funny old reason then, that green tea is so common place that we forget about its obvious benefits. Furthermore, it tastes too good, how could something which is so tasty be so health?

Well it can be!

So start drinking green tea today, because those befits of green tea are real!


Green tea benefits and Side Effects

While it’s great to talk about just how great green tea is and how many benefits, it possesses we must also remember that there, as always there is some downside.


Caffeine:                                                             For a start green tea has caffeine. Not as much as coffee, but still it is there. A small cup of green tea (8 ounces (120ml)) will have anywhere from 35 to 70mg of caffeine present. Compare this to coffee, and we see an 8 ounce cup of coffee having between 150-200mg of caffeine. So if we stick to the lower ends, which are 35mg and 150mg respectively, we see that coffee has about 4 times more caffeine than green tea. So as a general rule of thumb, green tea is far less of a stimulant than coffee. However, as a potential side effect of green tea, it must be noted that in some of the studies, referred to in this article, large qualities of green tea where consumed. Consequently, it is important to realise that large quantities of green tea will have a similarly stimulating effect, as noted with coffee consumption.

So if say you drink 4 cups of green tea, it is equivalent to 1 cop of coffee. If you are trying to detox, it might make sense to keep the green tea levels at the lower end, maybe 3 cups or less per  day, which is less than 1 cup of coffee. On the other hand if you want to perhaps make a big change to a specific health condition, such as say depression or blood pressure, for instance, a higher consumption, of green tea, for a limited period of time could be considered.


Green Tea Reactions with Certain Drugs


Amphetamines and cocaine:                                                      Have a bad effect when combined with green tea. Not that I would suggest anybody to take these kinds of drugs in the first place!

Ephedrine                                                                                            Is a stimulant and once combined with green tea could also produce a bad effect.

Adenosine (Aden card):                                                                 A heart medication reacts badly when combined with green tea.

Quinolone antibiotics:                                                                    When combined with green tea can result in an increase in side effects such as irritability, heart rate and headache.

Birth Control Pills and Cimetidine (Tagamet):                        Also run a risk of potential side effects which includes irritability, jitteriness and so on.


These side effects are actually unlikely to take place. More than Likely you will drink lots of green tea and feel fine; however, in some cases large doses of green tea may produce side effects in some cases.

If you feel any side effects, either reduce the quantity of green tea been imbibed or stop altogether.


In general the benefits of green tea far outweigh the side effects, so I would certainly recommend green tea to everyone. How much you take will vary of course, according to need and how your body reacts to green tea, but definitely 1 to 3 cups a day, will produce significant health benefits in the majority of the population.


Finally, the quality of green tea will vary quite a bit. How do you know if your green tea is good?


Well it should be green in colour and its tastes should be a little bit acerbic, which it will be if L-Theanine is present, and it should be, if it is concentrated green tea.

So f you don’t have any green tea in the house, start today, get drinking and focus on drinking regularly rather than drinking vast amounts, for a short period of time. On the various scientific trials noted in this article, the best benefits of green tea drinking where noted in subjects who were drinking green tea consistently, over s long period of time, as in 3 months or more. Do also remember that been a natural product, green tea will be slow to work, so don’t expect miracles; rather introduce green tea as a lifestyle Change and enjoy he benefits of green tea drinking!



  1. l-Theanine and caffeine improve task switching but not intersensory attention or subjective alertness

Suzanne J.L. Einöthera, , Vanessa E.G. MartensaJane A. RycroftbEveline A. De Bruina

a Sensation, Perception & Behaviour, Unilever R&D Vlaardingen, Vlaardingen, The Netherlands

b Lipton Institute of Tea, Unilever R&D Colworth, Sharnbrook, Bedford, United Kingdom

Received 3 September 2009, Revised 18 December 2009, Accepted 8 January 2010, Available online 15 January 2010

  1. L-theanine—a unique amino acid of green tea and its relaxation effect in humans

Lekh Raj Juneja**, , Djong-Chi Chu*Tsutomu Okubo*Yukiko Nagato*Hidehiko Yokogoshi

* Nutritional Foods Division, Taiyo Kagaku Co., Ltd, 1-3 Takaramachi, Yokkaichi, Mie 510-0844, Japan

 Laboratory of Nutritional Biochemistry, School of Food and Nutritional Sciences, The University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan

Available online 17 December 1999

3. Green tea consumption is associated with depressive symptoms in the elderly1,2,3

Kaijun NiuAtsushi HozawaShinichi KuriyamaSatoru EbiharaHui Guo,Naoki NakayaKaori Ohmori-MatsudaHideko TakahashiYayoi Masamune,Masanori AsadaSatoshi SasakiHiroyuki AraiShuichi AwataRyoichi Nagatomi, and Ichiro Tsuji

First published October 14, 2009, doi: 10.3945/ajcn.2009.28216Am J Clin Nutr December 2009 
vol. 90 no. 6 1615-1622

4. Preventive effects of drinking green tea on cancer and cardiovascular disease: Epidemiological evidence for multiple targeting prevention

Kei Nakachi*, Satoru Matsuyama, Satoshi Miyake,

Masami Suganuma andKazue Imai

Article first published online: 16 DEC 2008

DOI: 10.1002/biof.5520130109

5. Preventive effects of drinking green tea on cancer and cardiovascular disease: Epidemiological evidence for multiple targeting prevention

Kei Nakachi*, Satoru Matsuyama, Satoshi Miyake, Masami Suganuma andKazue Imai

Article first published online: 16 DEC 2008

DOI: 10.1002/biof.5520130109

6. The Major Green Tea Polyphenol, (-)-Epigallocatechin-3-Gallate, Inhibits Obesity, Metabolic Syndrome, and Fatty Liver Disease in High-Fat–Fed Mice1,2

Mousumi Bose3,5Joshua D. Lambert3,6Jihyeung Ju3Kenneth R. Reuhl4,

Sue A. Shapses5, and Chung S. Yang3,5,*

  1. Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin, and green teaKristel Diepvens, Klaas R. Westerterp, Margriet S. Westerterp-Plantenga

American Journal of Physiology – Regulatory, Integrative and Comparative Physiology Published 1 January 2007 Vol. 292 no. 1, R77-R85 DOI:10.1152/ajpregu.00832.2005

8.  Green Tea Catechin Consumption Enhances Exercise-Induced Abdominal Fat Loss in Overweight and Obese Adults1,2

Kevin C. Maki 3 , * Matthew S. Reeves 3 Mildred Farmer 4 Koichi Yasunaga 5 ,Noboru Matsuo 5 Yoshihisa Katsuragi 5 Masanori Komikado 5 ,Ichiro Tokimitsu 5 Donna Wilder 3 Franz Jones 3 Jeffrey B. Blumberg 6 , and Yolanda Cartwright 3

  1. Enhancement of Antioxidant and Phase II Enzymes by Oral Feeding of Green Tea Polyphenols in Drinking Water to SKH-1 Hairless Mice: Possible Role in Cancer Chemoprevention1

Sikandar G. Khan2Santosh K. KatiyarRajesh Agarwal3, and Hasan Mukhtar4

  1. Pharmacognosy Res. 2011 Oct-Dec; 3(4): 266–272.

doi:  10.4103/0974-8490.89748

PMCID: PMC3249787

Antioxidant and antibacterial properties of green, black, and herbal teas ofCamellia sinensis

Eric W.C. ChanEu Ying SohPei Pei Tie, and Yon Peng Law







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