The Green Tea Facade

Green tea has been consumed, mainly by Asian nations (having originated in China) for hundreds and hundreds of years. Over the course of history numerous and powerful heath effects have been attributed to frequent consumption of green tea.

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In the modern day, green tea and green tea based products are major staples of health food and fitness shops with much emphasis placed on it’s ‘fat melting’ properties.

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Green tea has also been linked to other extraordinary benefits…

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  • A cure for various cancers
  • Decreases risk of cardiovascular disease
  • Improves glycemic control
  • Reduces ‘bad’ cholesterol
  • A general reduction in risk of death
  • Reduces inflammation
  • Powerful weight loss aid

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These are all extraordinary claims which of course require extraordinary evidence. Luckily a fair amount of research has looked more closely at these proposed benefits…

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Is green tea beneficial to health: What does the science say?

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I’ve gone through the major ‘health benefits’ of green tea and addressed them below. Where possible I’ve used meta-studies to support my arguments. These are large scale reviews of all the available data on the topic and can provide stronger evidence than individual studies alone.

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Cancer: There are a few studies which make suggestive links between consumption of green tea and reduced risk of certain types of cancer in specific populations. A small decrease in esophageal cancer rates amongst the Chinese and slightly lower rates of oral cancers in Asian populations. (1, 2). However it is impossible to control for all variables in these sort of population studies and although overall cancer rates were very slightly lower in green tea drinkers, there are also many many other differences in lifestyle habits that could lead to this outcome.  When all current data is taken together, there is no firm, conclusive evidence that green tea consumption prevents or treats cancer  (3,4).

Search for 'green tea and cancer' and this is one of the first image results. Most of this is wrong. Pseudoscience like this is why I started this website in the first place. Red writing was added by me not some lunatic arguing with himself in an info graphic.
Search for ‘green tea and cancer’ and this is one of the first image results. Most of this is wrong. Pseudoscience like this is why I started this website in the first place. Red writing was added by me not some lunatic arguing with himself in an info graphic.

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Cardiovascular disease: A recent meta-study which compiled a large amount of data on this subject concluded that daily intake of green tea was associated with  a roughly 5% chance reduced risk of death from cardiovascular diseases (this includes things like heart attacks and stroke) (5). A well respected Cochrane review also compiled data from numerous randomised trials a few years previously and reported a small reduction in blood pressure associated with  tea consumption (6). In fitting with these findings, a number of other studies have suggested green tea consumption may also be associated with a reduced risk of stroke (7).

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Blood glucose control: Data here is a little bit messy. Green tea lowered fasting blood glucose in one trial but data generated on fasting insulin levels as well as glycated hemoglobin levels (used to determine longer term average blood glucose) was inconsistent (8,9). Both these references are large scale meta-studies so we can be fairly certain that green tea consumption has no real impact on glycemic control.

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Cholesterol: In this area green tea does appear to have some small but clear benefits. Another Cochrane review (can’t get enough) of longer term trials over 3 months in duration, concluded that green tea consumption lowers total blood cholesterol concentrations in the blood including LDL (low density lipoprotein) cholesterol sometimes called ‘bad cholesterol’ (10).

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LDL - Bad HDL - Goof
LDL – Bad
HDL – Good

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General risk of death: Two separate meta-studies concluded that frequent consumption of green tea resulted in a small reduction in the percentage chance of death from any cause (11,12).

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Inflammation: Green tea consumption is not associated with a significantly lower concentration of c-reactive protein in the blood. C-reactive protein is an acute phase protein from the liver that increases in response to macrophage and T cell activation so is used as a marker of inflammation (13).

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Green tea and pills containing concentrated green tea extract (catechins being the most important component) are  a multi-million dollar market. Although there is some suggestive evidence of small health benefits (see above), green tea is most commonly sold as a weight loss aid.

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But does it actually help with weight loss?

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Green tea is not a weight loss aid

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If you can convince people that your product will help them lose weight then you will make a guaranteed profit. The population is getting fatter and more than ever, people are desperate for a quick fix for weight problems.

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As you’ve guessed – there is no magic pill or easy fix for weight loss. It requires a maintained change to your eating and exercise habits.

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Ridiculous
Ridiculous

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Green tea is described on lots of product labelling as a ‘metabolic booster’ or ‘fat burner’. The main molecule that is often reported to be the ‘fat burner’ is a catechin called  epigallocatechin gallate (EGCG) . So what sort of conclusions are drawn from study’s looking at the ‘fat burning’ properties of green tea?

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Important point to bare in mind: Your average cup of green tea contains about 50-60 mg of EGCG

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One study from 2009 looked directly at the effects of green tea on body composition, measuring things like intra-abdominal fat, waist circumference and total body fat in control subjects and subjects receiving a varying amount of EGCG and caffeine. The group receiving the highest daily dose of EGCG and caffeine saw a clear reduction in all three measurements (14).

.Sounds great right?

.Well not really.

.This group was receiving 900 mg of EGCG a day as well as 200 mg of caffeine on top.

That’s the equivalent of about 18 cups of green tea and 5 cups of coffee...

Neither of which can be described as ‘healthy’ in the long term.

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Another study, published in 2008 approached from a different angle and looked at if green tea could enhance exercise-induced weight loss.

These participants were receiving over 600 mg of EGCG a day. The paper describes a ‘trend towards greater fat mass  loss in the catechin group’  which is another way of saying there was no statistically detectable difference between the groups. (15).

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What about claims that green tea ‘boost or increases metabolism’?

Short answer: It doesn’t.

A number of studies have shown that green tea consumption has no effect at all on the basal metabolic rate of healthy participants (16, 17). Importantly, these studies were measuring basal or resting metabolism . People peddling ‘fat burning’ green tea supplements want you to believe that green tea will simply burn away the extra calories all while you sit on the sofa. Impossible!

A more recent Cochrane meta-study, taking data from 18 separate studies and involving close to 2000 participants concluded that green tea does lead to small weight loss in obese people. However this is described as ‘non-significant and unlikely to be clinically important’. Additionally, green tea has no effect on weight loss maintenance (18).

All strong evidence that Green Tea or Green Tea Extract products are close to useless when it comes to weight loss. 

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Take home message

 

So what have we learned about green tea…

Commonly advertised attributes and the truth side by side:

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  • A cure for various cancers : No
  • Decreases risk of cardiovascular disease: Small reduction 
  • Improves glycemic control: Currently inconclusive
  • Reduces ‘bad’ cholesterol: Small but clear reduction 
  • A general reduction in risk of death: Potentially true but could be explained by many other variables
  • Reduces inflammation: No
  • Powerful weight loss aid: No

 

Although there is some evidence that green tea consumption can have health benefits such as a reduced risk of death from cardiovascular disease and a reduction in cholesterol, relying on supplements for this benefit isn’t necessary. Reducing your intake of trans fats and exercising more will provide you with these benefits plus many more.

In terms of the fat burning potential of green tea, it simply doesn’t exist. 

If you enjoy green tea then by all means enjoy a hot brew every now and then. However if you are forcing yourself to drink green tea for the advertised benefits  or paying through the nose for green tea extract pills then it’s not worth your time or money.

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Thanks for reading,

ScienceGuy

 

 

 

 

References

 

I recommend using Google Scholar for quick access to these studies.

1) Zheng JS, Yang J, Fu YQ, Huang T, Huang YJ, Li D (January 2013). “Effects of green tea, black tea, and coffee consumption on the risk of esophageal cancer: a systematic review and meta-analysis of observational studies”. Nutr Cancer (Systematic Review and Meta-Analysis). 65 (1): 1–16.

2) Wang W, Yang Y, Zhang W, Wu W (April 2014). “Association of tea consumption and the risk of oral cancer: a meta-analysis”. Oral Oncol (Meta-Analysis). 50 (4): 276–81.

3)  Boehm K, Borrelli F, Ernst E, et al. (2009). “Green tea (Camellia sinensis) for the prevention of cancer”. Cochrane Database Syst Rev (Systematic review) (3): CD005004

4) Johnson R, Bryant S, Huntley AL (December 2012). “Green tea and green tea catechin extracts: an overview of the clinical evidence”. Maturitas (Review). 73 (4): 280–7.

5) Tang J, Zheng JS, Fang L, Jin Y, Cai W, Li D (July 2015). “Tea consumption and mortality of all cancers, CVD and all causes: a meta-analysis of eighteen prospective cohort studies”. Br J Nutr (Meta-analysis). 114: 1–11.

6) Zhang C, Qin YY, Wei X, Yu FF, Zhou YH, He J (February 2015). “Tea consumption and risk of cardiovascular outcomes and total mortality: a systematic review and meta-analysis of prospective observational studies”. Eur J Epidemiology(Systematic Review and Meta-Analysis). 30 (2): 103–13.

7)  Khalesi S, Sun J, Buys N, Jamshidi A, Nikbakht-Nasrabadi E, Khosravi-Boroujeni H (September 2014). “Green tea catechins and blood pressure: a systematic review and meta-analysis of randomised controlled trials”. Eur J Nutr (Systematic Review and Meta-Analysis). 53 (6): 1299–1311

8) Liu K, Zhou R, Wang B, Chen K, Shi LY, Zhu JD, Mi MT (August 2013). “Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials”. Am J Clin Nutr (Meta-Analysis). 98 (2): 340–8.

9) Zheng XX, Xu YL, Li SH, Hui R, Wu YJ, Huang XH (April 2013). “Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials”. Am J Clin Nutr (Meta-Analysis). 97 (4): 750–62.

10)  Zheng XX, Xu YL, Li SH, Liu XX, Hui R, Huang XH (August 2011). “Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials”. Am J Clin Nutr (Meta-Analysis). 94 (2): 601–10.

11)  Tang J, Zheng JS, Fang L, Jin Y, Cai W, Li D (July 2015). “Tea consumption and mortality of all cancers, CVD and all causes: a meta-analysis of eighteen prospective cohort studies”. Br J Nutr (Meta-analysis). 114: 1–11.

12) Zhang C, Qin YY, Wei X, Yu FF, Zhou YH, He J (February 2015). “Tea consumption and risk of cardiovascular outcomes and total mortality: a systematic review and meta-analysis of prospective observational studies“. Eur J Epidemiology(Systematic Review and Meta-Analysis). 30 (2): 103–13

13)  Serban C, Sahebkar A, Antal D, Ursoniu S, Banach M (September 2015). “Effects of supplementation with green tea catechins on plasma C-reactive protein concentrations: A systematic review and meta-analysis of randomized controlled trials”. Nutrition (Systematic review & meta-analysis). 31 (9): 1061–71.

14) Wang et al  (August 2009). ”Effects of catechin enriched green tea on body composition” Obesity 18 (4):773-9

15) Maki et al (December 2008) ”Green tea catechin consumption enhances exercise-induced abdominal fat loss in overweight and obese adults” Journal of Nutrition  139(2):264-70.

16) Lonac et al (August 2010) ”Influence of short-term consumption of caffine-free EGCG supplement on resting metabolism and the thermic effect of feeding”.  Obesity  19(2):298-304.

17) Gregersen et al (May 2009) ”Effect of moderation intakes of different tea catechins and caffeine on acute measures of energy metabolism under sedentary conditions”Journal of Nutrition 102(8):1187-94.

18)  Jurgens et al (December 2012) ”Green tea for weight loss and weight maintenance in overweight or obese adults”.  Cochrane Library 

8 thoughts on “The Green Tea Facade”

  1. Excellent Article.

    Great to see some real science being put out among the myriad of Nonsense pedalled around on the internet. I will keep reading with great interest.

    Personally I quite like green tea. I drink it for pleasure and enjoyment. Not because I believe any perceived benefit! Its certainly better for you than Coke (or any other sugary drink)

    Keep up the Good work Debunking the quacks

    1. Cheers Steve,

      I feel like a needle in a haystack of quackery mate. But I will keep on fighting. it’s the only thing that keeps me sane.

      I quite like it as well as a drink but glad we are on the same page – A MUCH better option than most popular soft drinks.

      Who knows, maybe one day there will be more solid evidence regarding green teas and certain cancers but as of a right now a fat burner it is not!

  2. I like how you present a ton of information as well as linking to actual scientific studies. We need more people like you on the internet! Have you heard of green tea for use in skin care? You can get matcha green tea mask and green tea is an ingredient in a variety of skin care products. I am wondering if there have been studies done on that topic. I like to drink green tea because I like the taste and I like the lower caffeine than coffee, but I don’t expect it to work health miracles. You have to have a solid, healthy diet, exercise, restful sleeps and avoid toxins to stay healthy, not just drink some tea.

    1. Hi Andrea, thanks for commenting!

      Using plant products in cosmetic items has been going on for a long time now but recently we are seeing more research on the topic being produced. In theory EGCG is an anti inflammatory compound and also chemoprotective (as are lots of similar compounds) but this doesn’t seem to translate to health benefits when we drink green tea. However research is now looking at applying these compounds to cultured skin cells in vitro or in human patients. EGCG just rubbed into the skin doesn’t seem to have strong effects but techniques are now being explored that would inject EGCG (very shallow) into the skin – EGCG has a real problem getting past the most outer layers of the skin. It could potentially have skin protective or perhaps even restorative properties if it could be applied slightly deeper. If you would like to know more I suggest going to google scholar and typing in ‘green tea anti aging’. You will see a number of papers published this year which may interest you. I’m typing on my phone with spotty internet or I would link them to you myself!

      Please stop by again 🙂

  3. Man I am really glad I found this post. I have actually been taking decaffeinated green tea extract for the last six weeks.

    I had read about a study and the effects of EGCG and that it could actually help with fat loss. I have been losing fat but now I fear I am taking too much.

    What are the potential consequences of taking too much EGCG?

    1. Hi Jeremy, good to hear from you.

      When I cite studies, where possible, I try and use meta-studies which take all available data on a particular topic and produce a conclusion based on that – this can limit things like outcomes that happened by chance and not due to the intervention, in this case EGCG. Meta studies can range from a handful of studies to hundreds. It is true that some studies have found a link between EGCG and increased weight loss. However, most of these studies also include high levels of caffeine (a known stimulant which can produce weight loss by itself due to its effects on the sympathetic nervous system) alongside EGCG as well as being performed in obese people, whose metabolism is altered in numerous ways from people in the healthy weight bracket. It can therefore be misleading to take results from these sort of studies and tell people that EGCG will melt away the fat.

      I wouldn’t worry about taking too much EGCG although I’m not sure of the amount your supplement contains. Some of these weight loss studies gave participants the equivalent of 16 green tea cups worth of EGCG for an extended period of time. As far as I can tell, no health issues were reported because of this. I would be more worried about loading yourself up with caffeine but you did say it was decaffeinated which is a good thing – as high intakes of caffeine all the time can have negative side effects.

      You should be proud of your fat loss – you should take the credit not the EGCG supplement. The FDA has issued multiple warnings in the past to EGCG manufacturers who claim anti-disease or overall health benefits. None have been confirmed. My advice is to ditch the EGCG and carry on with what your doing because it’s clearly working.

      Cheers!

  4. It is true that green tea isn’t a solution for everything in this world. However, in America, it’s seen like some of miracle drug. People think it can be used for weight loss, diabetes, high blood pressure, cardiovascular diseases like angina and stuff. However, as you concluded, it’s just another beverage. To be fair here it does have its benefits, but people in America overexaggerate. In China, where the beverage originated from, it’s not used that way.

    1. Hi Blame,

      I think we are on the same page – things have been exaggerated with no real evidence. There is some very loose evidence, based on epidemiological studies, that drinking lots of green tea may reduce the rates of certain cancers including mouth and throat in Asian populations but this has yet to be confirmed. Numerous other lifestyle habits could produce this result.

      I also agree that it does have its benefits. Drinking tea, I find, is relaxing and soothing – both of which feedback into overall health by reducing stress. Drinking lots of tea is also hydrating which is an added bonus.

      Thanks for stopping by

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Filtering out the pseudoscience