Tea is the most widely consumed beverage worldwide, second to water. The incredible health benefits of green tea are not news to most people. Green tea benefits your health as an antioxidant, anti-inflammatory, antimicrobial, anticarcinogenic, antihypertensive, brain protector as well as lowers cholesterol.
Some of the downsides may be less well known. We will begin here with a review of some of the most well studied benefits of green tea.
EGCG (Epigallocatechin gallate) & Cancer
In the last decade, there has been a good deal of research showing the anti-cancer properties of green tea and it’s main constituent, epigallocatechin gallate (EGCG), showing positive results in epidemiological, cell culture, animal and human studies in various types of cancer.
Cell culture studies, including those on the polyphenols in green tea, show that tea polyphenols increase apoptosis (programmed cell death) and arrest cell proliferation in tumor cells but not in normal, healthy cells.1 Animal studies also show that treatment with green tea can decrease cancerous tumors in skin, colon, liver, mammary glands and stomach.
Breast Cancer therapies utilizing the catechins of green tea have been studied extensively in the past two decades. The research has varied significantly, in terms of in vivo or in vitro, carcinogens looked at, green tea catechin dose used, and whether or not it was green tea extract or a synthetic version that is higher in EGCG. The effect is not always statistically significant, but what is consistently found is the protective effect of green tea in all of the breast cancer trials. This suggests that further trials of green tea extracts should be done, particularly in high-risk women. 7
Estrogen receptor alpha cells responded better to tamoxifen in the presence of EGCG. And growth of non-malignant breast epithelial cells is not affected by EGCG. 5
Researchers studying the nanoparticles of green tea found that while they did not have the EGCG (or caffeine or theobromine) that has been studied so heavily, they did have a benefit in cancer therapy. They form a complex with doxorubicin and improve the uptake of the drug into cancer cells. This led to increased cytotoxicity of lung cancer and breast cancer cells. They also were found to have increased uptake and cytotoxicity in multi-drug resistant breast cancer cells. 6
EGCG has been shown to have very potent free-radical quenching capabilities, which is especially important in detoxification and preventing oxidative damage.
More studies are needed to determine which populations and which organ systems are likely to benefit the most from green tea consumption. But there is sufficient evidence to know at this point that it does help keep cancer at bay, and without much downside, can be assumed to be a reasonable tonic to include in your daily diet.
Theanine & Anxiety
Recent years have seen large increases in data available on the central nervous system effects of theanine. Theanine is an amino acid component of both green and black teas, although is somewhat higher in green tea. L-theanine is the form in supplements for human use. It was previously thought it should be taken as a supplement to achieve the greatest calming effect, rather than to just have a cup of green tea. Recent research shows that it crosses the blood brain barrier, increasing alpha brain waves, even with just a simple cup of green tea. Alpha waves are seen on EEG and mostly found in wakeful relaxation with eyes closed. This seems to help people focus on mental tasks. The unique quality of theanine is that it helps produce alert focus while also producing a sense of calm. Many calming herbs and pharmaceuticals also create sleepiness. Not so with theanine. Although if your anxiety is keeping you awake, theanine may help induce sleep just by reducing anxiety levels. The calming effect of theanine is related to it’s upregulation of inhibitory neurotransmitters, while also regulating dopamine and serotonin levels in the brain. 2 Other areas where theanine shows some promise include stroke recovery and schizophrenia.
Polyphenon E and Cervical Cancer
Polyphenon E is a topical ointment with a standardized amount of epigallocatechin gallate (EGCG) from green tea. It has been used in several studies showing elimination of HPV related warts. 3 It has also been shown in cell cultures to reduce cervical cancer by inducing apoptosis and inhibition of telomerase activity. 4
Green Tea and Anti-Aging
Tea has been used since ancient times for it’s proposed health benefits. Now we are coming up with scientific research to help prove this and also to understand the mechanisms of action. Several new research studies have recently been published that show the benefits of green tea on effects of aging.
Polyphenolic compounds from green tea contain compounds that show strong affinity to reactive oxygen species. They show the ability to neutralize free radical damage and initiate other positive biological effects. 10
Emulsions of green tea and lotus applied to the skin are shown to reduce wrinkles, scaliness and skin roughness. Green tea and lotus were also each studied alone in this trial and were found to have synergistic effects when applied together. 8 Another meta-review of studies of botanicals for skin wrinkles showed no benefit with green tea, but also pointed out at that the study designs were not adequate. 9 More research is needed in this area.
Another review article pointed out that green tea has a beneficial effect in limiting skin cancer growth, along with reducing ultraviolet light induced photoimmunosuppresion. 12
Diabetes and Heart
Green tea has been shown to help with metabolic disorders including insulin resistance, type 2 diabetes, hypertension, and decrease cholesterol. 11
What about the bad stuff?
If you’ve been reading so far waiting for the other shoe to drop, fear not. It isn’t so bad. At least nothing that you can’t avoid with a little education.
Look out for toxic elements!
Canadian researchers recently studied 30 different types of black, green and oolong teas found on local store shelves. They looked at both regular and organic teas. They looked at toxic elements in the tea leaves themselves, tea brewed for 3 minutes and then tea brewed for 15-17 minutes. Here is the heartbreaking news: all teas contained lead. In the teas brewed for just 3 minutes, 73% contained lead, and in the tea brewed for 15-17 minutes 83% contained lead at levels that are considered unsafe for pregnancy and lactation. There was no difference in lead levels between organic and regular teas. 13
Interestingly, while many of the tea leaves contained mercury, no mercury was found in the brewed teas. There is some binding that occurs in the tea leaves that keeps it from leeching out in to the tea.
And while choosing tea that is organic isn’t necessarily going to protect you from the elevated lead levels, purchasing tea from different countries certainly could. The study showed that all green tea from China, organic and regular, had elevated lead levels. While tea from Sri Lanka did not. Organic green tea from Japan showed moderate levels of lead, arsenic and cadmium.
Take it easy on cream and sugar!
Tea flavonoids protect cells from free radical damage. This is because tea contains high levels of antioxidants, the polyphenols we’ve talked about already. But many people are doctoring up their tea with things that completely eliminate the activity of these antioxidants. As it happens, more people do this to black tea than to green. Researchers showed that the addition of milk, sugar and honey decrease the antioxidant levels in tea in a dose-dependent manner. Addition of the natural sweetener stevia had no negative effect on the antioxidant levels, so it should be the sweetener of choice in any tea. 14
Where do we go from here?
It is clear that green tea has many beneficial qualities. Having several cups each day can provide myriad health benefits. My favorite way to have my green tea is to brew kombucha – that way I get the catechins and some probiotics all in one place. But we need to be smart to avoid any negative attributes. Educate yourself about where your tea comes from. Most of us tend to drink the same brand over and over again. Find out where it’s grown and if they do any testing to make sure it does not have toxic contaminants. If you are taking a concentrated green tea capsule for medicinal purposes, I would do the same research. Make sure that you aren’t also getting concentrated lead. Many of the best supplement companies do regular testing to make sure there are no toxins in their products. If they aren’t, I wouldn’t take it.
And for sure stay away from milk and sugar in your tea.
- Chen, D et al, Green tea and tea polyphenols in cancer prevention. Front Biosci. 2004 Sep 1;9:2618-31. PMID:15358585
- Yokoyama, M. The tea polyphenol, (-)-epigallocatechin gallate effects on growth, apoptosis, and telomerase activity in cervical cell lines. Gynecol Oncol. 2004 Jan;92(1):197-204.
- Garcia, FA. Et al. Results of a phase II randomized, double-blind, placebo-controlled trial of Polyphenon E in women with persistent high-risk HPV infection and low-grade cervical intraepithelial neoplasia. Gynecol Oncol. 2014 Feb;132(2):377-82. doi: 10.1016/j.ygyno.2013.12.034. Epub 2014 Jan 2.
- Zeng L, et al. Effects of physiological levels of green tea extract epigallocatechin-3-gallate on breast cancer cells. Front Endocrinol (Lausanne). 2014 May 7;5:61. doi: 10.3389/fendo.2014.00061. eCollection 2014.
- Yi S, et al. Tea nanoparticles for immunostimulation and chemo-drug delivery in cancer treatment. J Biomed Nanotechnol. 2014 Jun;10(6):1016-29.
- Yiannakopoulou ECh Effect of green tea catechins on breast carcinogenesis: a systematic review of in-vitro and in-vivo experimental studies.Eur J Cancer Prev. 2014 Mar;23(2):84-9. doi: 10.1097/CEJ.0b013e328364f23e.
- Mahmood, T. Combined topical application of lotus and green tea improves facial skin parameters. Rejuvenation Res. 2013 Apr;16(2):91-7. doi: 10.1089/rej.2012.1380.
- Hunt, KJ, Botanical extracts as anti-aging preparations for the skin: a systematic review. Drugs Aging. 2010 Dec 1;27(12):973-85. doi: 10.2165/11584420-000000000-00000.
- Hsu S. Green Tea and the skin. J Am Acad Dermatol. 2005 Jun;52(6):1049-59.
- PloS One. 2014 Jan 3;9(1):e84468. doi: 10.1371/journal.pone.0084468. eCollection 2014.
- Barbosa, NS. CAM use in dermatology. Is there a potential role for honey, green tea, and vitamin C? Complement Ther Clin Pract. 2014 Feb;20(1):11-5. doi: 10.1016/j.ctcp.2013.11.003. Epub 2013 Nov 20.
- Schwalfenberg G, et al. The benefits and risks of consuming brewed tea: Beware of toxic element contamination. J Toxicol 2013. 370480.
- Korir, MW. The fortification of tea with sweeteners and milk and its effect on in vitro antioxidant potential of tea product and glutathione levels in an animal model. Food Chem. 2014 Feb 15;145:145-53. doi: 10.1016/j.foodchem.2013.08.016. Epub 2013 Aug 11.