Green tea, made of the leaves of the Camellia sinensis plant, first originated in Asia and is now grown in various hot and humid regions of Asia, Africa, and Oceania. Green tea leaves and leaf buds are harvested from the tea plant, processed to remove their moisture content, and roasted until their characteristic green color is achieved. The tea is also screened to remove unwanted particles, then graded into various varieties to be sold commercially. (9)
Green tea benefits
Some of the benefits of green tea include its antioxidant and potential anti-cancer effects, as well as its role in supporting cardiovascular, cognitive, and metabolic health.
Green tea is a source of water-soluble antioxidants known as catechins, which make up approximately 30% of the dry leaf. (9) The four primary catechins in green tea leaves include:
- Epigallocatechin gallate (EGCG)
- Epicatechin gallate (9)
Green tea catechins act as scavengers of reactive oxygen and nitric oxide free radicals, which are unstable compounds that are associated with cellular damage and diseases such as Alzheimer’s disease, atherosclerosis, cancer, and diabetes. (2)(9) Antioxidants function by neutralizing free radicals before damage can occur. (2)
Green tea may have a protective effect against certain cancers, such as breast cancer. Research in China compared the effects of green tea in 1,009 females with confirmed breast cancer to 1,009 age-matched healthy controls. The study found that green tea intake was associated with a reduced risk of breast cancer. The relationship was dependent on the amount and duration of tea consumption, which suggests that regular consumption of green tea may provide greater protective effects. (12) Although some evidence supports these anti-cancer effects, the National Cancer Institute doesn’t currently support the use of green tea to reduce cancer risk. (6)
You may have already heard of the heart-healthy benefits of drinking green tea, which may also be attributed to its catechin content. A meta-analysis of controlled trials including liquid green tea and green tea supplements found that green tea and catechins may improve blood pressure, particularly in individuals with elevated systolic blood pressure (above 130 mm Hg). Green tea intake was also associated with reduced total and low-density lipoprotein (LDL) levels. (4) These findings suggest that green tea may have a role to play in the prevention of cardiovascular disease.
If you’re looking for help with that afternoon slump, stressful exam, or presentation at work, then green tea may be your cup of tea. A review assessed 21 studies that investigated the effects of green tea and green tea extracts on brain function and cognition. The researchers concluded that green tea was associated with reduced symptoms of anxiety and improved attention and memory, as well as improved working memory function demonstrated by MRI scans. These benefits may be a result of the combination of caffeine and the amino acid L-theanine, as the effects were stronger when both substances were present. (6)
Green tea can also support your metabolic health. Green tea catechins may support glucose (blood sugar) control by reducing the absorption of carbohydrates in the intestines, enhancing insulin sensitivity, and regulating gluconeogenesis, a process occurring in the liver that produces glucose. (11)
A systematic review and meta-analysis examined the effect of green tea supplementation on glycemic control. The study found that short-term (generally less than 12 weeks) supplementation lowered fasting blood glucose levels. The authors specified that longer intervention trials of green tea supplementation are needed to assess its effect on hemoglobin A1c (HbA1c) concentrations, a measure of average blood sugar levels over preceding two to three months. (11)
How to include green tea in your diet
Green tea is most commonly found in loose-leaf form or packaged in tea bags, but you can also try it as matcha tea. Matcha green tea is made from tea plants that are shade-grown. After harvest, the leaves are ground into a fine powder. This powder is whisked and dissolved into hot water or milk. Matcha makes a delicious, rich-tasting drink that you can enjoy as a substitute for coffee or black tea.
Green tea caffeine content
If you’re limiting caffeine intake, green tea may be a better choice than coffee. A standard 8 oz cup of green tea has approximately 35 mg of caffeine, compared to 100 mg for brewed coffee. (3) Keep in mind that decaffeinated green tea may not provide the same benefits, as research has shown that decaffeination decreases the amount of volatile compounds in the tea. (5)
Green tea supplements
This medicinal plant is commonly found in supplement form as green tea extract (GTE). GTE supplements contain L-theanine, individual catechins such as EGCG, and numerous other active constituents. (10) If you’re a patient, we always recommend speaking with your integrative healthcare practitioner prior to trying a new supplement.
The bottom line
Green tea offers more than a delicious cup of aromatic tea. It’s been enjoyed for centuries for its therapeutic properties, and emerging research is now supporting some of these health claims. Green tea is high in antioxidants and may protect against certain health conditions, which are great reasons to incorporate green tea into your diet! (4)(8)(9)
- Chu, C., Deng, J., Man, Y., & Qu, Y. (2017). Green tea extracts epigallocatechin-3-gallate for different treatments. BioMed Research International, 2017, 1–9.
- Hajhashemi, V., Vaseghi, G., Pourfarzam, M., & Abdollahi, A. (2010). Are antioxidants helpful for disease prevention? Research in Pharmaceutical Sciences, 5(1), 1–8.
- Heckman, M. A., Weil, J., & de Mejia, E. G. (2010). Caffeine (1, 3, 7-trimethylxanthine) in foods: A comprehensive review on consumption, functionality, safety, and regulatory matters. Journal of Food Science, 75(3), 77–87.
- Khalesi, S., Sun, J., Buys, N., Jamshidi, A., Nikbakht-Nasrabadi, E., & Khosravi-Boroujeni, H. (2014). Green tea catechins and blood pressure: A systematic review and meta-analysis of randomised controlled trials. European Journal of Nutrition, 53(6), 1299–1311.
- Lee, S., Park, M. K., Kim, K. H., & Kim, Y.-S. (2007). Effect of supercritical carbon dioxide decaffeination on volatile components of green teas. Journal of Food Science, 72(7), S497–S502.
- Mancini, E., Beglinger, C., Drewe, J., Zanchi, D., Lang, U. E., & Borgwardt, S. (2017). Green tea effects on cognition, mood and human brain function: A systematic review. Phytomedicine, 34, 26–37.
- Namita, P., Mukesh, R., & Vijay, K. J. (2012). Camellia sinensis (green tea): A review. Global Journal of Pharmacology, 6(2), 1.
- National Center for Complementary and Integrative Health. (2016, November). Green Tea. Retrieved from https://www.nccih.nih.gov/health/green-tea
- Poonam, V., Archita, M., Deepali, S., Hemant, G., & Himanshu, S. K. (2018). A review on: Green Tea: A miraculous drink. International Journal of Pharmaceutical Sciences Review and Research, 51(2), 26–34.
- Saldanha, L., Dwyer, J., Andrews, K., Betz, J., Harnly, J., Pehrsson, P., … Savarala, S. (2015). Feasibility of including green tea products for an analytically verified dietary supplement database. Journal of Food Science, 80(4), H883–H888.
- Xu, R., Bai, Y., Yang, K., & Chen, G. (2020). Effects of green tea consumption on glycemic control: A systematic review and meta-analysis of randomized controlled trials. Nutrition & Metabolism, 17(1), 56.
- Zhang, M., Holman, C. D. J., Huang, J., & Xie, X. (2006). Green tea and the prevention of breast cancer: A case-control study in Southeast China. Carcinogenesis, 28(5), 1074–1078.