By: Samuel Mathis, MD, Assistant Professor, UTMB
“All I need in life is Jesus and my green tea.” – Mary Mathis (my grandmother)
One question often asked by Integrative Medicine physicians is how much green tea an individual drinks daily. At Integrative Medicine conferences, green tea is everywhere. I am fairly sure I even saw a green tea beer on tap one year ago. And why wouldn’t we love green tea? It is one of the healthiest drinks ever created outside of clean drinking water. What is it that makes green tea so healthy?
First, green tea contains numerous health-boosting compounds, such as flavonoids and catechins – specifically epigallocatechin-3-gallate (EGCG), L-Theanine, and phenolic acid. These compounds have antioxidant properties, improve cognition, and even help prevent damage to the brain from aging (1). There are studies that have found decreased levels of inflammation in the body and brain from drinking 3-5 cups of green tea per day (2). These compounds decrease and even reverse some of the oxidative damage caused by pro-inflammatory foods and other harmful substances. A large systematic review in 2016 found that EGCG acted as an antioxidant to scavenge reactive oxygen species and even attenuated nuclear factor-kB activity (2).
There are even some studies that have linked green tea consumption to decreased risk of developing certain types of cancers like lung cancer or ovarian cancer. There are some studies that have shown the compounds in green tea may also limit the growth of certain cancers like esophageal, lung, and pancreatic cancers, but these were not conclusive. In 2020, a Cochran systematic review update of 142 studies found that these benefits are inconsistent, though there are numerous RCTs and case-controlled studies that indicate the protective benefits of green tea consumption. One caveat to these studies is that the bulk were carried out in Asian populations, which limits the generalizability of these studies (3). Studies have not shown that green tea can treat cancer, but my grandmother swore that green tea played a huge role in treating her cancer.
In addition to its inflammatory and cancer-prevention properties, green tea has also been shown to help with certain chronic health conditions such as diabetes and cardiovascular health (1). Drinking green tea daily is estimated to lower one’s risk of death from diabetes by up to 10%. Other studies have found green tea slightly helps with blood sugar control, lowering the risk of hyperglycemia. Green tea also lowers the risk of heart disease through blood pressure and cholesterol-lowering effects. However, these studies are small, and further research is needed to verify these results.
Green tea has also been shown to improve fat utilization, thus increasing the effectiveness of weight loss. This is why so many weight loss supplements utilize green tea extract. Again, while some studies have shown green tea helps, other studies have not shown it to be effective.
Some caution in green tea ingestion may be required. Individuals with caffeine sensitivity or a history of liver injury should use caution in drinking significant amounts of green tea. Side effects of overconsumption include nausea, vomiting, diarrhea, headache, and loss of appetite (caffeine overdose). The caffeine in green tea can also interact with medications such as beta-blockers, some antibiotics, and some seizure medications. There is some concern that the antioxidants in green tea may interact with chemotherapy agents and some monoamine oxidase inhibitors and can even lower lithium levels. For these reasons, I typically recommend patients drink 2-3 cups of green tea daily. Many of my patients will “reuse” their green tea bags, which still give the benefit of the phenols without the added caffeine. Loose-leaf tea is usually better than tea bags as the risk of food fraud is high in many versions of various teas (some have been found to have lawn clippings in them).
Finally, one study in Japan found that individuals who drank 5 cups of green tea per day had lower all causes of mortality than those drinking 1 cup or less. A follow-up study confirmed these findings and found that drinking 7 cups a day lowered the risk of death by up to 62% compared to non-drinkers (4). Whatever the case may be, green tea is something that should be added to all our diets to help improve our overall health. I use a little honey in mine to sweeten it up without ruining the anti-inflammatory effects by adding sugar. Add some lemon and it tastes great either hot or over ice on a hot summer day.
References:
- Chacko, S.M., Thambi, P.T., Kuttan, R., Nishigaki, I., 2010. Beneficial effects of green tea: A literature review. Chinese Medicine 5, 13.. https://doi.org/10.1186/1749-8546-5-13
- Ohishi T, Goto S, Monira P, Isemura M, Nakamura Y. Anti-inflammatory Action of Green Tea. Antiinflamm Antiallergy Agents Med Chem. 2016;15(2):74-90. doi: 10.2174/1871523015666160915154443. PMID: 27634207.
- Filippini T, Malavolti M, Borrelli F, Izzo AA, Fairweather-Tait SJ, Horneber M, Vinceti M. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database Syst Rev. 2020 Mar 2;3(3):CD005004. doi: 10.1002/14651858.CD005004.pub3. PMID: 32118296; PMCID: PMC7059963.
- Abe SK, Saito E, Sawada N, Tsugane S, Ito H, Lin Y, Tamakoshi A, Sado J, Kitamura Y, Sugawara Y, Tsuji I, Nagata C, Sadakane A, Shimazu T, Mizoue T, Matsuo K, Naito M, Tanaka K, Inoue M; Research Group for the Development and Evaluation of Cancer Prevention Strategies in Japan. Green tea consumption and mortality in Japanese men and women: a pooled analysis of eight population-based cohort studies in Japan. Eur J Epidemiol. 2019 Oct;34(10):917-926. doi: 10.1007/s10654-019-00545-y. Epub 2019 Aug 7. PMID: 31392470.