Almost everyone nowadays knows that Green tea is an amazing beverage that is extremely good for health. This article takes a deeper look at the benefits of Green tea consumption and any associated risks.
Green tea is rich in polyphenolic compounds, with catechins as its major component. Studies have shown that catechins possess diverse pharmacological properties that include anti-oxidative, anti-inflammatory, anti-carcinogenic and anti-bacterial effects.
Overall, Green tea has other benefits like anti-arteriosclerotic, anti-arthritic, anti-angiogenic, anti-viral, neuroprotective and cholesterol-lowering effects1 (Chacko et al., 2010).
The health benefits of consuming this tea are substantial. Let’s take a look at some of the potential benefits of green tea…
Benefits of Green tea
1. Prevent Cancer
Green tea possesses powerful anti-angiogenic properties that may help prevent cancer.
Cancer is one of the most terrible diseases in the 21st century. The fact that it has no guaranteed cure makes it even more terrifying.
So it comes as great news to know that there are studies2, 3 (Kavanagh et al., 2001; Sueoka et al., 2001) that have experimented on human cells and observed that Green tea has significant inhibitive effects on cancer cell proliferation.
Another similar study11 (Sartippour et al., 2002) indicated that Inhibition of (VEGF) transcription appeared to be one of the molecular mechanism(s) involved in the anti-angiogenic effects of green tea, which may contribute to its potential use for breast cancer treatment and/or prevention.
To put the aforementioned study in context, vascular endothelial growth factor (VEGF) is a signal protein produced by cells that stimulates the formation of blood vessels9 (Wikipedia). In healthy humans, VEGF promotes angiogenesis (process through which new blood vessels form from pre-existing vessels) in embryonic development and is important in wound healing in adults. Research10 (Carmeliet et al., 2005) has shown that it is the key mediator of angiogenesis in cancer.
2. Prevent Cardiovascular Diseases
Cardiovascular diseases (esp. those involving heart failure) are one of the leading causes of death in the world.
A study3 (Sueoka et al., 2001) found a decreased relative risk of death from cardiovascular disease for people consuming over 10 cups of green tea a day.
3. Prevent A Host of Inflammatory Diseases
Green tea possesses strong anti-inflammatory properties.
Inflammation in the body can lead to a wide array of diseases like allergy, auto-immune diseases, coeliac disease, hepatitis, inflammatory bowel disease etc.
Neutrophils (a type of White blood cells) in the human body are essential for both host defence (immunity) and inflammation. Neutrophil elastase is a derivative of the same and is known as the most destructive enzyme in human body as it results in the destruction of the bacteria and host tissue as part of its functioning. Usually this works in our favour as part of immune function. But once unregulated, this enzyme can wreak havoc in the body4 (Kawabata et al., 2002).
There is evidence5 (Donà et al., 2003) that epigallocatechin-3-gallate (EGCG) in Green tea, strongly inhibits the functioning of neutrophil elastase and hence, may be used as a potential anti-inflammatory agent.
4. Weight Loss
Green tea has been reported to have several benefits relating to weight loss.
A randomized study33 (Boschmann & Thielecke, 2007) was conducted among six overweight men on the effect of epigallocatechin-3-gallate (EGCG) – the main catechin in green tea – with regards to fat oxidation. The results suggested that green tea consumption increases fat oxidation and has anti-obesity properties.
Another study32 (Venables et al., 2008) conducted among healthy young men on the effect of green tea extracts on fat oxidation reported that during moderate to intense exercises, the rate of fat burn was higher in people who consumed green tea.
5. Reduce Blood Pressure
Increased blood pressure is one among the indicators of metabolic syndrome. Green tea consumption has reportedly been observed to reduce blood pressure.
A 2013 study6 (Mousavi et al., 2013) conducted in healthy subjects between ages 35-65 years and BMI 25-35 showed that drinking four cups of green tea led to a significant reduction in weight and systolic blood pressure.
6. Prevent Arthritis
Arthritis is a common problem associated with old-age. Arthritis is basically a case of inflammation of one or more of your joints.
The anti-oxidative properties of Green tea may be useful in dealing with this disease.
There is evidence7 (Haqqi et al., 1999) that suggests that a polyphenolic fraction from green tea that is rich in antioxidants may be useful in the prevention of onset and severity of arthritis.
7. Fight Infections
Green tea may be helpful in fighting bacterial and viral infections.
Bacterial infections are the cause of many diseases and resistant infections. The epigallocatechin-3-gallate (EGCG) in Green tea has been studied to have several antibacterial activities that limit bacterial growth and invasion and act in synergy with beta-lactam antibiotics.
In fact, a study8 (Sudano et al., 2004) in 2004 suggested the possible use of EGCG as an adjuvant in antibacterial therapy.
It was observed in another study19 (Weber et al., 2003) on adenovirus infection that Green tea catechins (specifically epigallocatechin-3-gallate (EGCG)) was the most effective when added to the cells during the transition from the early to the late phase of viral infection suggesting that EGCG inhibits one or more late steps in virus infection.
8. Prevent Cholesterol
Cholesterol that is oxidized within the body tends to promote the formation of fatty deposits in the arteries. This can lead to serious health issues like stroke.
One study12 (Osada et al., 2001) that monitored the anti-oxidative potency of Green Tea Catechins against copper catalysed Low-density lipoprotein (LDL or “bad” cholesterol) oxidation showed that epigallocatechin-3-gallate (EGCG) had significant anti-oxidative property.
Another study13 (Raederstorff et al., 2003) provides evidence suggesting that the cholesterol-lowering effect of green tea is mainly elicited by EGCG, one of the most abundant catechins contained in green tea. The study suggests that one of the underlying mechanisms by which EGCG lead to a decrease in cholesterol absorption is by interfering with the breakdown, synthesis and solubilisation of cholesterol in the digestive tract.
9. Prevent Gastrointestinal Disorders
Research14 (Koo et al., 2004) indicates that Green tea is effective to prevent dental caries and reduce cholesterols and lipids absorption in the gastrointestinal tract. Tea catechins are well absorbed in the gastrointestinal tract and interact synergistically for disease-modifying actions.
This makes drinking unfractionated green tea the most simple and beneficial way to prevent gastrointestinal disorders.
10. Prevent Metabolic Syndrome
Metabolic syndrome is the name for a cluster of risk factors that raises your risk of contracting heart disease, stroke and type-2 diabetes.
Results obtained from a study15 (Ikeda, 2008) suggest a possibility that tea catechins and heat-treated tea catechins with the galloyl moiety (critical structural feature of green tea catechins that inhibits fatty-acid synthase (FAS)) improve lipid metabolism and contribute to the prevention of the metabolic syndrome16 (Wang et al., 2003).
11. Protect From Neuro-Degenerative Diseases
Green tea may help protect from progressive neurodegenerative diseases like Parkinson’s and Alzheimer’s diseases.
Mounting evidence suggests a key role of oxidative stress and inflammation in the development of neurodegenerative and cognitive deficits in individuals of advanced age.
Studies18 (Weinreb et al., 2004) conducted on this front have resulted in green tea polyphenols being considered as therapeutic agents for these diseases due to their anti-oxidative and anti-inflammatory properties.
12. Prevent Skin Disorders
Solar ultraviolet radiation (UVR) light is a complete carcinogen and repeated exposure can lead to the development of various skin disorders including melanoma and non-melanoma skin cancers.
Research20 (Katiyar et al., 2003) conducted on this provides evidence to indicate that green tea polyphenols are photo-protective in nature and may be used as pharmacological agents for the prevention of solar UVB light-induced skin disorders including photo-aging, melanoma and non-melanoma skin cancers.
13. Promotes Oral Health
Green tea may help in improving oral health and have a protective effect on teeth. This is because green tea has been indicated to have significant anti-cariogenic (anti-decaying) and anti-bacterial properties to improve oral health.
In Green tea, the main players are its most abundant catechins (like epigallocatechin-3-gallate (EGCG)) that are in much lower concentration in other tea varieties23 (Goenka et al., 2013).
One pilot study28 (Awadalla et al., 2011) held in 2011 on the role of green tea use on oral health supported the thesis that local application of green tea as anti-bacterial and anti-cariogenic material decreases the acidity of the saliva and plaque and hence, may be considered as a cost-effective decay prevention measure.
Another study29 (Hirasawa et al., 2006) that investigated the effect of epigallocatechin-3-gallate (EGCG) solution on dental plaque pH suggested that it is effective in reducing acid production in dental plaque and mutans streptococci.
Yet another study30 (Koyama et al., 2010) of 2010 that examined the association between green tea consumption and tooth loss observed that consumption of atleast 1 cup/day of green tea was significantly associated with decreased odds for tooth loss.
The findings of a study31 (Ferrazzano et al., 2011) that showed a statistically significant reduction in colony counts of mutans streptococci and lactobacilli bacteria in the mouth after use of Green tea extract opened up a promising avenue of clinical applications in the preparation of specific and natural anti-cariogenic remedies centred around Green tea.
14. Prevent Asthma Attacks
Caffeine in Green tea (and other teas, for that purpose) has been found to have an inhibiting effect on asthma attacks.
A Cochrane Airways Group trial24 (Welsh et al., 2010) concluded that caffeine helped to improve airways function modestly up to 4 hours after ingestion.
15. Reduce Hair Fall
Hair fall is a common dermatological problem affecting both men and women. It is hereditary and is mainly caused by the hormone Dihydrotestosterone (DHT).
Here also, the caffeine in tea comes into play.
One study25 (Bansal et al., 2012) suggested that the beneficial effects of applying caffeine may be attributed to the inhibition of DHT, inhibition of phosphodiesterase, improvement in barrier function, follicular penetration, stimulation and promotion of hair growth.
Another interesting study26 (Yesudian, 2012) conducted in 2012 on whether caffeine containing beverages can regrow hair on bald heads observed that it may indeed be possible in the future and that the prospect has sufficient promise to warrant more research. The researchers in this study were able to cultivate human hair follicles from balding areas of bald male patients and observe the differential stimulatory effects of caffeine in varying doses. It was shown that 0.001% of caffeine prevented the suppressive effect of testosterone on the cultured hair follicles.
Please note that the point made here is about caffeine content and hence, may be applicable to any beverage containing the same (not just Green tea).
16. Improve Cognitive Ability
Green tea may help to maintain mental alertness and cognitive function. The main potential effect of all teas is its impact on the central nervous system. This is mainly the impact of caffeine.
Green tea has caffeine and an amino acid called L-theanine in quantities of 6.56 and 16.28 mg/g approximately. Caffeine works as a stimulant whereas L-theanine has a relaxing effect. In fact, Green tea has the highest caffeine content among all 4 teas prepared from Camellia sinensis shrub27 (Boros et al., 2016).
The Recommended Quantity of Intake
Speaking strictly from a Green tea based context, the required quantity differs across the medical condition that you are trying to avoid. The reason for this is that different studies used different amounts of Green tea to get their desired results. This ranges from 2 cups in a day to more than 10 cups in a day.
Hence, this information may not be very useful due to the isolated nature of the study and when read in conjunction with the deleterious effects of tea.
Common dosage for human consumption is usually 1-2 cups a day. In these dosages, on a consistent basis, you may be able to reap the benefits of Green tea. Consumption in moderation is safe for most people. Since you probably already drink atleast 1-2 cups of tea/coffee per day, this should be okay (provided you substitute them for Green tea) to consume.
It is, nonetheless, advisable to consult your doctor to make sure that your individual case does not constitute a scenario where you should avoid Green tea. This is especially true if you intend to increase your consumption beyond the common dosage.
What Makes Green Tea So Amazing?
Polyphenol content in Green tea, particularly catechins, flavanols and flavonols, is the major factor that makes it one of the healthiest drinks in the world. They constitute about 30% of fresh leaf dry weight of Green tea leaves. Its most abundant catechin – epigallocatechin-3-gallate (EGCG) – has been identified as a key component that boasts of many health benefits. <Cite reference 1>
A research17 (Eng et al., 2018) found EGCG to exhibit a myriad of therapeutic properties including anti-atherosclerosis, anti-cardiac hypertrophy, anti-myocardial infarction, anti-diabetes, anti-inflammatory and antioxidant.
These were mainly explained by the below cause-effect details:
- Inhibition of LDL cholesterol –> anti-atherosclerosis
- Inhibition of NF-κB –> anti-cardiac hypertrophy
- Inhibition of MPO activity –> anti-myocardial infarction
- Reduction in plasma glucose and glycated haemoglobin level –> anti-diabetes
- Reduction of inflammatory markers –> anti-inflammatory
- Inhibition of ROS generation –> anti-oxidant
Are There Any Risks To Consumption Of Green Tea?
From the cases and studies available over the years, three factors jump out as potential issues:
- Caffeine sensitivity – Green tea contain caffeine and other components available in similar tea groups. If you are sensitive to caffeine or any such components, it is better to consult with your doctor about it before making a habit of it.
- Combination effects with other drugs – If you are on medications, it is better to consult with your doctor regarding potential deleterious combinatorial effects. This includes reduced efficiency of some medications taken to reduce anxiety and depression, reduced efficiency of medications like beta blockers used for heart disease etc.
However, study22 (Pain et al., 2018) says that such effects are very less pronounced (if at all they occur) in common dosages of human consumption.
- Fluoride content in low-quality Green tea – A study21 (Lu et al., 2004) indicated that the fluoride level in some teas (including Green tea) increased along with a decrease in tea quality.
Fluoride is a Schedule 6 Poison, teratogen and bio-accumulative, endocrine disruptor that has no nutritional value. The acute lethal dose of Fluoride for humans is less than 5 milligram of Fluoride per kilogram of body weight. The World Health Organization (WHO) states that Fluoride is more toxic than Lead and slightly less toxic than Arsenic.
A safe dosage is estimated to be 0.0010 mg Fluoride/kg-day [Hirzy 2016]. This implies that the expected dosage is supposed to be decided using ALARA principle, i.e. keeping exposure reduced to As Low as Reasonably Achievable22 (Pain et al., 2018).
However, this is more or less the case with other tea categories as well. So if you do decide to consume Green tea (or any tea for that purpose), we suggest you opt for the highest quality possible.
- Potential Pregnancy risks – It is advised by researchers that women in the third trimester of pregnancy avoid foods that contain high concentrations of polyphenol (like Green tea) to avoid risk of triggering constriction of ductus arteriosus which has potential harmful consequences such as foetal and neonatal heart failure and pulmonary arterial hypertension of the new-born22 (Pain et al., 2018).
The name of the game, as always, is moderation. So if you are a tea-lover, you might want to check out our article on the health hazards of tea so that you may make an informed decision and find a sweet spot where your satiety coincides with medically safe proportions.
Carmeliet P. VEGF as a key mediator of angiogenesis in cancer. Oncology. 2005;69 Suppl 3:4-10. Epub 2005 Nov 21. https://www.ncbi.nlm.nih.gov/m/pubmed/16301830/