Green tea has been consumed throughout Asia for centuries. Tea is made from dry leaves from the plant camellia sinesis, and the tea from this plant is categorised by how it is processed. Green tea is non-oxidised, oolong tea is partially oxidised, and Black Tea is fully oxidised. What are the benefits of drinking green tea?
The benefits of drinking green tea is widely reported, but what is the research showing in relation to these benefits and how much do we need to drink to see a benefit to our health?
Full of antioxidants, green tea is the most consumed beverage throughout the world. An antioxidant called catechin is present in high amounts in green tea. Natural compounds called polyphenols are contained in high quantities in green tea, and researchers believe the benefits are mostly related to the polyphenol content within the green tea.
Reducing cancer risk
The benefits of green tea has been studied and some research has linked green tea compounds with a reduced risk of cancers such as colorectal cancer, lung cancer due to melanoma and breast cancer.
- Colorectal Cancer
One study showed that the reoccurrence rate for colorectal cancer was lower when consumed green tea and green tea extras when compared to a control group (1).
- Lung Cancer
Green tea has shown inhibitory effects on spreading of cancer cells in certain types of cancer such as melanoma which has spread to the lungs (3).
- Breast Cancer
Some research has shown that reoccurrence rate for stage I and stage II breast cancer was lower consuming more than 5 cups of green tea per day (3). In saying that, the Western Australia Cancer Council (2) state that there is conflicting evidence between green tea and cancer risk, but drinking 3-5 cups per day is likely to do no harm.
Cardiovascular benefits of green tea
Harvard Health (5) released a paper in 2012, which indicated that green tea may lower blood triglycerides and bad cholesterol (LDL) levels. With a diet high in processed foods, it is not uncommon to see younger people have high cholesterol levels. I have covered other foods that benefit cholesterol levels here.
A Japanese study found adults who consumed 5 cups of green tea per day had a 26% decreased risk of dying from a stroke or heart attacks, and 16% lower death rate from other diseases (5).
What are the weight-loss benefits of drinking green tea?
Some evidence shows that consuming green tea may reduce visceral body fat around the abdominal area. Research has shown that catechins found in green tea can reduce visceral fat, body fat and body weight was decreased significantly (8). Excessive visceral body fat can be detrimental to one’s health, increasing heart attacks, stroke and Metabolic Syndrome.
Lower your risk of type II diabetes
Diabetes rates are increasing year to year, especially in western countries. Some studies have shown that people who drink green tea can have an 18% reduced risk of diabetes (7). Other benefits of green tea consumption may include improved insulin sensitivity and improved blood glucose levels.
Benefits of green tea for people with metabolic syndrome
Some early research suggests that body mass index, waist circumference, fasting blood glucose, systolic blood pressure and bad cholesterol dramatically improved in people consuming green tea (10). Although the study did show not many changes in total cholesterol, cholesterol levels (HDL) and diastolic blood pressure. To improve some of these aspects could improve the health of people with metabolic syndrome.
How many cups per day is beneficial?
It is commonly agreed that 3-5 cups per day of green tea could be beneficial but should be consumed wisely due to some potential side effects (5). The side effects of drinking green tea are rare but may include elevated liver enzymes, which has been shown in various animal research studies. Green tea is a rich source of oxalate, which may form kidney stones (5). And nobody has time for that.
More research is required.
Given conflicting opinions regarding the anti-cancer effects and preventative actions of green tea, I believe the jury is still out on this. There are several published research articles that there is not enough research showing the anti-cancer effects of green tea alone in clinical trials in humans, and further research is needed (4).
More research is needed on how the catechins in green tea reduce the risk of a specific disease and any other clinical effects of these substances. Definitely watch this space!
- Sabu M Chacko, Priya T Thambi, […], and Ikuo Nishigaki. Beneficial effects of green Tea: A literature review. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2855614/
- Cancer Council WA. Cancer myth: Coffee, Tea, hot beverages and cancer. Retrieved from https://www.cancerwa.asn.au/resources/cancermyths/coffee-tea-myth/
- Miyata, Y., Matsuo, T., Araki, K., Nakamura, Y., Sagara, Y., Ohba, K., & Sakai, H. (2018). Anti-cancer Effects of Green Tea and the Underlying Molecular Mechanisms in Bladder Cancer. Medicines (Basel, Switzerland), 5(3), 87. https://doi.org/10.3390/medicines5030087
- Miyata, Y., Shida, Y., Hakariya, T., & Sakai, H. (2019). Anti-Cancer Effects of Green Tea Polyphenols Against Prostate Cancer. Molecules (Basel, Switzerland), 24(1), 193. https://doi.org/10.3390/molecules24010193
- Harvard Health. Green tea may lower heart attack risk. Retrieved from: https://www.health.harvard.edu/heart-health/green-tea-may-lower-heart-disease-risk#:~:text=Lowering%20your%20risk%20of%20cardiovascular,from%20heart%20disease%20and%20stroke.
- Babu, P. V., & Liu, D. (2008). Green tea catechins and cardiovascular health: an update. Current medicinal chemistry, 15(18), 1840–1850. https://doi.org/10.2174/092986708785132979
- Huxley R, Lee CMY, Barzi F, et al. Coffee, Decaffeinated Coffee, and Tea Consumption in Relation to Incident Type 2 Diabetes Mellitus: A Systematic Review With Meta-analysis. Arch Intern Med. 2009;169(22):2053–2063. doi:10.1001/archinternmed.2009.439
- Ying Zhang, Yingjie Yu, Xu Li, Shinichi Meguro, Satoshi Hayashi, Mitsuhiro Katashima, Takeshi Yasumasu, Jingzhong Wang, Keji Li,
- Effects of catechin-enriched green tea beverage on visceral fat loss in adults with a high proportion of visceral fat: A double-blind, placebo-controlled, randomised trial, (2012). Journal of Functional Foods, Volume 4, Issue 1. https://doi.org/10.1016/j.jff.2011.12.010.
- Emerald Insights. (2018). Effect of green tea consumption on the metabolic syndrome indices in women: a clinical trial study. Retrieved from https://www.emerald.com/insight/content/doi/10.1108/NFS-03-2018-0091/full/html