Green Tea Supplements: The Pros & Cons

What Are Green Tea Supplements?

With hundreds of millions of regular users, green tea is one of the most popular caffeinated beverages in the world.  On top of that, its extract is also featured in hundreds of different dietary supplements and taken by millions of people.     

Green tea extract is, not surprisingly, derived from green tea leaves, which come from the Camellia Sinesis plant.  Like the drink, green tea extract also contains caffeine along with natural compounds called catechins.

While plenty of research has demonstrated the positive effects of caffeine, there is also an ample body of evidence to suggest that catechins may offer several additional health benefits as well.  

What Benefits Are Associated with Green Tea?

⫸Boost Energy

Many different energy products feature green tea extract as one of their central ingredients.  That’s because countless studies have shown that caffeine helps to improve everything from alertness and cognition to reaction time and overall sports performance.   

Caffeine primarily works by inhibiting the action of the chemical messenger adenosine, which amongst other things, helps to produce feelings of tiredness when released in your body.  There is also some evidence that caffeine may help to boost the concentration of serotonin and epinephrine in your brain, which is why it's often labeled as a nootropicsubstance.        

⫸It’s an Antioxidant

The other central ingredient in green tea -- catechins -- act as antioxidants, helping to block the build-up of free radicals.  Free radicals are unstable molecules that can cause cellular damage, increase oxidative stress, and raise your risk of illness and disease.  

Several studies, however, have shown that catechins like epigallocatechin-3-gallate (EGCG), which is the most abundant catechin found in green tea, help to reduce oxidative stress and improve cellular health and longevity. ^(1)(2)(3)

⫸May Improve Brain Function

Catechins also appear to have neuroprotective properties helping to reduce oxidative stress and inflammation in the brain.  Catechins like EGCG aid in the prevention of brain cell damage by blocking the build-up of free iron on your brain’s neurons, which may help to improve your performance when it comes to memory and cognition-related tasks.⁽⁴⁾⁽⁵⁾

⫸Support Cardiovascular Health

On top of reducing oxidative stress, research also shows that catechins may benefit your cardiovascular health in several ways as well.  A number of studies have demonstrated that regular green tea consumption helped to reduce LDL cholesterol levels in study participants.⁽⁶⁾⁽⁷⁾

Other research has also illustrated that green tea may help to lower your blood pressure and reduce inflammation in your arteries, which in turn, may help to lower the risk of cardiovascular disease.⁽⁸⁾

⫸May Help With Weight Loss

In addition to keeping your heart healthy, there is also some evidence that catechins may help to promote weight loss, although findings are mixed. ^(9)(10)

Some researchers argue that EGCG helps to increase the physiological process known as thermogenesis.  Thermogenic compounds may help you to burn up more calories by increasing the amount of heat your body produces.⁽¹¹⁾

However, it’s important to point out that the number of extra calories you burn off as a result of ingesting green tea is likely pretty small.  While it might be a helpful tool for some, eating right and exercising regularly are far more effective when it comes to losing weight.  

Are There Any Risks Associated With Green Tea Supplements?

While a number of benefits have been associated with drinking green tea, the National Institute of Health (NIH) suggests that unlike the beverage, green tea extract may pose some potential dangers to your health.   

More specifically, the NIH has reported over 50 cases of acute liver injury in individuals who took dietary supplements containing green tea extract.  While most people were able to recover with treatment, several fatalities have also been reported. ⁽¹²⁾

In most cases, liver injury occurred inside of 4 months, with symptoms typically arising anywhere from 10 days to several months after supplementation began.   The issue appears to be linked to an excessive intake of EGCG. While they may be beneficial to your health at lower levels, research shows that catechins can become toxic to your liver at high dosages.    

Depending on how it's produced, green tea extract can have extremely high concentrations of EGCG (and other catechins) but these levels can vary significantly from one product to another, which may help to explain why some weight loss products have been directly associated with liver injury while others have not.  

Many products containing green tea extract also don’t clearly state how much EGCG is in each dose, which makes it much more difficult to know how much you’re taking in per day.            

This can be problematic especially when it comes to individuals taking green tea extract for weight loss.  In fact, nearly all cases of liver injury reported by the NIH were directly linked to weight loss products such as Hydroxycut, Dexatrim, and Slimquick.  

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For instance, a case study published in the Annals of Internal Medicine reported that a 37-year-old woman with no history of liver disease developed jaundice along with abdominal pain and nausea around 4 months after she began taking a weight-loss product containing green tea extract.⁽¹³⁾ 

Lab test ultimately revealed that her serum aminotransferase (ALT) levels were 20 times greater than normal and a liver biopsy showed significant necrosis and inflammation.

A 2015 study published in the Journal of Food and Chemical Toxicology explored the effects of green tea extract in postmenopausal women at risk for breast cancer.⁽¹⁴⁾ 

While the researchers did report some positive findings, they also found that 6.7% of the study participants who were given green tea extract ultimately demonstrated elevated aminotransferase (ALT) levels, which can be a sign of liver injury -- when your liver is damaged, it often releases more ALT in your blood.  

Research suggests that certain factors like fasting and obesity, as well as micronutrient deficiencies, may increase the risk of liver injury when coupled with green tea supplements.    

In addition, taking green tea extract with other medications can significantly increase the risk of liver toxicity as well.  For example, one of this article's authors did not realize that he was combining green tea extract with 4 other known liver toxins and suffered reversible hepatitis.

Such common medications that may inadvertently add significant risk include:

• Tylenol (acetaminophen)
• Amoxicillin and Augmentin (antibiotics)
• Antidepressants like Paxil, Wellbutrin, and Lexapro
• Asprin
• Anit-viral agents like Acyclovir for Herpes
• Aloe-Vera
• Maca
• Niacin
• Red Yeast Rice and Statins

There are literally hundreds of medications and supplements that can potentially increase the likelihood of liver injury when combined with green tea extract. So if you're on other medications or are taking other supplements, you'll certainly need to do your research before throwing green tea extract into the mix.

While there is still some debate when it comes to tolerability, research suggests that the chances of liver damage start to increase significantly when you go over 21 mg of green tea extract per kilogram of body weight each day.   The NIH reports that the maximum dose tolerated in humans is 9.9 grams per day, which breaks down to over 20 cups of tea.  

So Should You Take Green Tea Extract?

While there does appear to be more risk involved in using green tea extract compared to just having a cup of tea, there are several things you can do to minimize the danger.  

When it comes to boosting your energy level, one of the easiest ways to minimize the risks associated with green tea extract is simply to get your caffeine from another source.  If switching over to a cup of tea or coffee is not for you, then you may want to consider an energy supplement without green tea extract.  

With that being said, if you're more interested in it for the health benefits, there are several things you can do to make sure you’re consuming green tea extract safely and effectively.  The first thing is to look for reputable products that clearly state how much EGCG is in each dose.   

On top of that, you can also take green tea extract with other substances that help to reduce the risk of liver damage.  For instance, doctors commonly recommend n-acetylcysteine (NAC) and milk thistle to drug overdose patients to help reduce liver toxicity.⁽¹⁵⁾

Wrap Up

While drinking green tea may be associated with a number of different health benefits, research shows that green tea extract can potentially become dangerous when taken in large quantities. More particularly, the catechin EGCG can be toxic to your liver when consumed in excess.

On top of making sure you're not consuming too many catechins, if you are taking a green tea supplement, you'll also want to make sure that you're not on other medications that can potentially alter or exacerbate its effects.

• References
  1. “Prevention of cytotoxicity and inhibition of intercellular communication by antioxidant catechins isolated from Chinese green tea” Ruch, R.J., Cheng, S., Klaunig, J.E. Carcinogenisis. Jun. 1989.
  2. “In vivo antioxidant effect of green and black tea in man.” Serfini, M., Ghiselli, A., Ferro-Luzzi, A. European Journal of Clinical Nutrition. Jan. 1996.
  3. “Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement.” Henning, S.M., Niu, Y., Lee, N.H., Thames, G.D., Minutti, R.R., Wang, H., Go, V.L.W, Heber, D. The American Journal of Clinical Nutrition. Dec. 2004.
  4. “Green tea catechins as brain‐permeable, natural iron chelators‐antioxidants for the treatment of neurodegenerative disorders” Mandel, S., Amit, T., Reznichenko, L., Weinreb, O., Youdim, M.B.H. Molecular Nutrition. Feb. 2006.
  5. “Protective effect of green tea polyphenol EGCG against neuronal damage and brain edema after unilateral cerebral ischemia in gerbils” Lee, H., Bae, J.H., Lee, S.R. Neuroscience Research. Aug. 2004.
  6. “Green Tea Catechins Decrease Total and Low-Density Lipoprotein Cholesterol: A Systematic Review and Meta-Analysis” Kim, A., Chiu, A., Barone, M.K., Avino, D., Wang, F., Coleman, C.I., Phung, O.J. Journal of the American Dietetic Association. Nov. 2011.
  7. “Chinese green tea lowers cholesterol level through an increase in fecal lipid excretion” Yang, T.T.C., Koo, M.W.L. Life Sciences. Dec. 1999.
  8. “Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials” Zheng, X., Xu, Y., Liu, X., Hui, R., Huang, X. The American Journal of Clinical Nutrition. Aug. 2011.
  9. “The effects of green tea on weight loss and weight maintenance: a meta-analysis” Hursel, R., Viechtbauer, W., Westerterp-Plantenga, M.S. International Journal of Obesity. July. 2009.
  10. “Effect of green tea on resting energy expenditure and substrate oxidation during weight loss in overweight females” Diepvens, K., Kovacs, E.M.R., Nijs, I.M.T., Vogels, N. British Journal of Nutrition. Dec. 2005.
  11. “Drug Record: Green Tea” National Institute of Health. July. 2019.
  12. “Repeated dose studies with pure Epigallocatechin-3-gallate demonstrated dose and route dependant hepatotoxicity with associated dyslipidemia” Ramachandran, B., Jayavelu, S., Murhekar, K., Rajkumar, T. Toxicology Reports. 2016.
  13. “Repeated dose studies with pure Epigallocatechin-3-gallate demonstrated dose and route dependant hepatotoxicity with associated dyslipidemia” Bonkovsky, H.L. Annals of Internal Medicine. Jan. 2006.
  14. “Repeated dose studies with pure Epigallocatechin-3-gallate demonstrated dose and route dependant hepatotoxicity with associated dyslipidemia” Ramachandran, B., Jayavelu, S., Murhekar, K., Rajkumar, T. Toxicology Reports. 2016.
  15. “The effect of N-acetyl-l-cysteine (NAC) on liver toxicity and clinical outcome after hematopoietic stem cell transplantation” El-Sefari, I., Remberger, M., El-Serafi, A., Benkessou, F., Zheng, W., Martel, E., Ljungman, P., Mattsson, J., Hassan, M. Scientific Reports. May. 2018.