Green Tea, one of the popular varieties of tea, is produced using only the leaves and boiled water buds of the plant Camellia Sinensis. It may surprise many that the origins of the green tea and the black tea are the same species, however, green tea manufacture does not involve the process of drying or oxidation, unlike black teas.
Camellia sinensis is said to have its origin in the Yunnan Province of China with around 260 of the 380+ varieties of tea found there. Legend says that Emperor Shennong of China, considered by many as the inventor of Chinese medicine, discovered green tea in 2737 BC by accident when some fresh tea leaves fell into his cup of boiled water. Buddhist monks from Japan who visited China took seeds to grow tea back home for its calming effects and refreshing energy.
While the origins of green tea can be traced back to China, its production and manufacture is since widespread and has a global presence in 50+ countries such as Japan, India, Bangladesh, Kenya, Sri Lanka, Taiwan, Hawaii and as far away as South Carolina.
The Nutritional Content of Green Tea
The manufacturing process for green tea is quite distinctive and commences as soon as the tea leaves from the Camellia Sinensis plant are harvested. Soon after cleaning, either a pan-fried method or steaming is undertaken to dry the leaves without too much oxidation, as it would result in the green leaves turning brown and change the unique flavor.
Green tea, if brewed correctly, will be light-colored and possess a mildly astringent quality. Depending on the process, the flavor is either grass-like and toasty in pan-fired teas or sweet, vegetal kind of flavor in steamed teas.
The nutritional content of green tea is varied with
- Amino acids (glycine, theanine, leucine, arginine, etc.),
- Carbohydrate (pectin, cellulose, fructose, etc.),
- Minerals (calcium, magnesium, iron, copper, zinc, etc.),
- Pigments (chlorophyll, carotenoids),
- Linoleic acids,
- Vitamins (B, C, E),
- Xanthic bases (caffeine, theophylline) and
- Volatile compounds (aldehydes, esters, alcohols, etc.)
The most important component of green tea is the heavy presence of polyphenols which are flavonols or catechins. 30% of the dry content of green tea is made up of these phenolic compounds which have high antioxidant properties. Catechins are of 4 types namely epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG). The most abundant catechin is EGCG, which is proven by many studies to provide various health benefits to the human body.
The 12 Proven Health Benefits of Green Tea
Green Tea has been used in traditional Chinese, Japanese and Indian medicine for treating various conditions such as reducing anxiety, increasing energy, treating hangovers, improving mood, aid digestion, etc. Scientific studies have also backed green tea’s polyphenolic compounds in promoting various health benefits. Listed are some of the proven health benefits of green tea.
1. Green Tea Polyphenols Have Therapeutic Properties
Green Tea is abundant in polyphenols that are proven to have high antioxidant properties. Research has found that these polyphenols are 25 and 100 times more powerful than vitamins E and C respectively. The polyphenols in green tea provide several benefits by fighting free radicals to reduce inflammation, fight cancer, obesity, and protect from cell damages and cardiovascular disorders.
Research has classified EGCG or epigallocatechin gallate in green tea as one of the most powerful and potent catechins well-known for its beneficial effects. Apart from its antioxidant properties, EGCG is proven to have therapeutic properties that can help prevent various health issues such as cholesterol, diabetes, inflammation and heart diseases. Studies show that the compounds epigallocatechin (EGC) and EGCG possess antimicrobial properties and green tea consumption can ensure the distribution of these compounds throughout the body to prevent infectious diseases.
Summary: Green tea’s content of polyphenols, especially EGCG, possesses antioxidant properties that help protect the body from free radical damage and fight various diseases.
2. Green Tea Improves Memory and Cognitive Ability
Cognitive abilities are skills associated with learning, planning, recalling, reasoning and abstract thinking. Green tea has been researched by various studies to see if its content of amino acids, catechins and caffeine could help enhance memory and cognitive abilities in humans.
Research has shown that green tea intake may have a positive impact on cognitive functions, especially working memory. Another study showed that green tea drinking may improve working memory in relatively older women.
Studies have also shown that the antioxidants in green tea catechins can help improve spatial learning abilities. The caffeine present in green tea is believed to boost cognition, memory, alertness, and mood in human beings. Green tea contains the amino acid l-theanine which is shown to increase brain chemicals serotonin and dopamine to exert neuroprotective effects and also improve cognitive abilities such as learning and memory. One study showed that the presence of both caffeine and l-theanine in green tea can have significant effects on attention, memory, and less distraction.
Summary: Green tea phytochemicals have been proven to have a positive impact on the brain and help in improving cognitive abilities in humans.
3. Green Tea Helps Burn Fat
Obesity is a condition where fat accumulation in the body is uncontrolled and excessive to the extent that it has adverse effects on an individual’s health and well-being. As obesity can lead to various hazardous health conditions including cardiovascular diseases, fat loss through weight management becomes vital. Green tea has been a popular choice for many who want to lose weight and scientific research confirms its efficacy in aiding weight loss.
Studies show that green tea with its powerful catechins and caffeine content may promote weight management by inhibiting fat accumulation and obesity and increasing the body’s metabolic rate. Green tea seems to work by using its thermogenic properties to increase energy expenditure and promote fat oxidation to effectively aid in weight control. One study indicated that green tea intake during moderately-intensive exercises enhances fat oxidation and promotes insulin sensitivity and glucose tolerance in healthy young men. An overall impression from several studies suggests that green tea consumption every day, with EGCG doses between 100 and 460mg, may result in a significant reduction of body fat and weight when taken for periods of 12 weeks or more.
Summary: Green tea with its catechins and caffeine content can increase energy expenditure and fat oxidation when taken daily for continuous periods to help lose fat and aid in weight loss.
4. Green Tea May Help Lower Risk of Cancer
Cancer is a disease in which abnormal cells multiply rapidly and invade part(s) of a body destroying body tissue and eventually the organ(s). Green tea has been one of the top food choices to prevent or aid in the treatment of cancer owing to its powerful polyphenols presence. The polyphenols which have high antioxidant properties may help in fighting oxidative stress which can trigger inflammatory pathways to turn normal cells into tumors.
A comprehensive search of studies on breast cancer has revealed that green tea consumption of 5 cups a day may likely reduce the recurrence of breast cancer in early stages but the data collected is limited and still not conclusive. Another study indicated that men who had a regular intake of green tea had a decreased risk of having advanced prostate cancer. A specific study showed that green tea may have a protective effect on female and rectal cancer patients and daily consumption may have an inverse effect on colorectal cancer risk.
Summary: Various studies have shown that green tea with its antioxidant capabilities may help in preventing the recurrence of cancer. Those with regular intake of green tea may have a lower risk of having cancer.
5. Green Tea May Lower Risk of Neurodegenerative Diseases
Neurodegenerative diseases such as Alzheimer’s, Parkinson’s disease occur due to the progressive decline of the central and peripheral nervous system in the human body. These diseases affect the body’s capabilities such as movement, gait, speech, memory, etc. Green tea has been intensively studied for efficacy in reducing the risk of such neurodegenerative diseases.
Studies have explored and indicated that green tea polyphenols may exert neuroprotective effects that are beneficial in the treatment of neurodegenerative diseases. Another study suggested that a ‘colon-available’ extract (CAGTE) after gastrointestinal digestion was shown to exhibit anti-proliferative effects and ameliorated cytotoxicity induced by specific free radicals such as hydrogen peroxide and beta-amyloid. The neuroprotective properties of green tea catechins, especially EGCG, is thought to decrease dementia incidence in Alzheimer’s and Parkinson’s diseases.
Summary: The polyphenols in green tea especially EGCG may help reduce dementia, inhibit free radicals and exert neuroprotective capabilities that may benefit the treatment of neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases.
6. Green Tea May Improve Dental Health
Dental health, given minimal importance by many people, has a primary role to play in maintaining the overall health and wellbeing of every individual. Poor oral hygiene, besides causing cavities, bad breath and gum disorders, is also known to lead to serious conditions such as diabetes, cancer, and risk of cardiovascular diseases. Green tea in scientific studies has shown the potential to safeguard oral health in various ways.
Studies indicate green tea may support periodontal health by reducing inflammation and inhibiting the proliferation of bacteria that are linked to periodontal diseases. The antibacterial properties of green tea extracts can be effective in preventing dental caries and other periodontal diseases. Dental caries are mainly caused by bacteria such as Streptococcus mutans and Lactobacillus acidophilus and the antimicrobial and antibacterial properties of green tea seem to be effective in fighting these bacteria. Studies also support the fact that green tea can be effective in lowering bad breath owing to its disinfectant and deodorant properties.
Summary: Green tea has the potential to eliminate harmful bacteria that can cause dental infections and helps prevent caries and bad breath.
7. Green Tea Can Help Manage Diabetes
The World Health Organization (WHO) has estimated that 400+ million people in the world are affected by diabetes and it is the 7th leading cause of death globally. Type II is the most common type of diabetes but is treatable. Consumption of certain foods has been known to help manage diabetes and green tea has been at the forefront of such foods. Research says that drinking beverages such as green tea and coffee may prove helpful in lowering the risk of type II diabetes.
A meta-analysis of various studies shows that green tea may effectively improve insulin sensitivity and help in controlling glucose levels in the body. Another study on mice and humans’ intake of green tea showed that regular intake of green tea in the evenings was more beneficial in reducing postprandial glucose levels in humans. A study on mice with type I and type II diabetes showed that green tea consumption could reduce blood glucose levels and also lowered the plasma fructosamine and glycated hemoglobin concentrations.
Summary: Various studies support green tea’s efficacy in managing diabetes. Regular consumption of green tea has shown to reduce glucose levels and improve insulin sensitivity in diabetics.
8. Green Tea May Help Protect From Heart Disease
Heart diseases also referred to as Cardiovascular Diseases (CVD) is responsible for more than 17 million deaths each year around the globe but yet 80% of them are treatable. Smoking, stress, cholesterol, blood pressure levels are all markers for CVDs. Green tea with its anti-inflammatory and anti-carcinogenic properties has been intensely studied for its effects in lowering the risk of CVDs.
A study on the mortality rate due to all causes including CVD showed that those who drank 5 cups of green tea had a significantly lower risk of dying due to CVD. Another study showed that the intake of green tea consumption could result in a lowered risk of Coronary Heart Disease (CHD) mainly in middle-aged and older Chinese populations.
A study of green tea on cholesterol, one of the major markers of heart disease, indicated that habitual consumption of green tea every day may promote a significant reduction in Total Cholesterol (TC) and LDL concentrations in the body. Another meta-analysis of 15 studies suggests that green tea catechins may improve blood pressure especially systolic pressure, which is again one of the important factors to consider in heart diseases. In a specific study on smoking and green tea consumption, it was found that regular green tea consumption reduced oxidative stress in healthy smokers through its antioxidant properties. Also, the presence of ascorbic acid in green tea was considered beneficial to prevent atherosclerotic vascular disease.
Summary: Green tea has been proven beneficial to lower the risk of CVDs and also manage other factors such as smoking, blood pressure, and cholesterol that may contribute to CVDs.
9. Green Tea May Promote Weight Loss and Prevent Obesity
Obesity is a condition where excess body fat may become dangerous and lead to major health complications such as heart disease. Weight management with a good diet and active lifestyle can help in preventing or reducing obesity. Green tea has been backed by research as part of a healthy diet to help manage weight.
In scientific studies, about 11 relevant articles provided information that catechins, specifically EGCG, showed a positive impact on weight loss and weight management, with ethnicity and caffeine being moderators. A meta-analysis on the effect of green tea found that a continuous 8-week intervention with green tea could help maintain a stable fasting blood insulin and reduce waist circumference in Type II Diabetes Mellitus (T2DM) patients.
One study on obese Thais revealed that green tea was capable of reducing body weight by increasing the energy expenditure and fat oxidation process in these subjects. Another study on high-catechin green tea intake on body composition suggested that green tea consumption reduced abdominal fatness and improved body composition in moderately overweight Chinese people.
Summary: Scientific research back green tea for its potential to reduce waist circumference, increase energy expenditure to induce weight loss and improve body composition to prevent the risk of obesity.
10. Green Tea May Help Treat Inflammatory Diseases
Inflammatory diseases refer to ailments of the sin and other parts of the body characterized primarily by inflammation. Hepatitis, Inflammatory Bowel Disease (IBD), Autoimmune diseases, etc. all fall into this category. Green tea polyphenols have studied for their beneficial effects owing to their antioxidant and anti-inflammatory capabilities.
Studies have shown that green tea polyphenols lower inflammatory responses by controlling cytokines and inflammatory markers to protect against various diseases such as hepatitis, colonic and neurodegenerative complications. Another study on the effect of green tea on psoriasiform lesions indicated that the polyphenols in green tea may have therapeutic effects on psoriasiform disorders.
Specific studies of green tea effects on autoimmune disease showed that green tea extracts have potential anti-inflammatory effects and can serve as an excellent curative agent as well as a food supplement in the treatment of intraocular autoimmune inflammation.
A deeper study of EGCG effects on vascular inflammation in Rheumatoid arthritis (RA) revealed that experiments showed a visible reduction in vascular inflammation. Though more studies are necessary to state facts and mechanisms clearly, researchers agreed that green tea may provide benefits in managing RA.
Summary: Green tea polyphenols, in various studies, have displayed commendable effects in the treatment of various inflammatory disorders. More studies may be necessary to accentuate green tea effects on certain conditions.
11. Green Tea May Help Preserve Bone Health
Bones provide structure, enhance muscle formations, shield organs from damage and store calcium to provide support, gait, and strength to the body. Bone loss may occur over time and it becomes essential to maintain bone density to prevent conditions such as osteoporosis. Scientific journals and certain other studies conclude that general tea consumption can lower the risk of osteoporosis.
Scientific studies have shown that green tea can mitigate bone loss due to aging, obesity and chronic inflammation. The effect of green tea polyphenols in female rats has shown that it displayed bone-protective properties that could enhance antioxidant capacity and decrease oxidative stress.
Another study of green tea extracts on bone markers proved that green tea supplementation combined with Tai Chi exercise had a positive impact on serum markers of bone turnover such as bone-specific alkaline phosphate (BAP) and tartrate-resistant acid phosphatase (TRAP), calcium metabolism and an increase in muscle strength in postmenopausal osteopenic women.
Summary: Green tea polyphenols can help reduce bone loss, improve serum markers of bone turnover and enhance antioxidant capabilities to protect bones from oxidative stress.
12. Green Tea May Protect Eye Health
Eye health is considered vital as 80% of perception is dependent on vision. Neglecting eye health can have a drastic impact on the quality of life. Cataract, macular degeneration, diabetic retinopathy are some of the common conditions or diseases that affect the eye. Green tea catechin presence has been studied for their efficacy in supporting eye health.
Age-related macular degeneration (AMD), if untreated, is known to cause visual impairment or even blindness. Specific studies show that green tea polyphenols may help treat retinal degeneration and be beneficial in patients suffering from AMD. Owing to its antioxidant properties, green tea consumption of over 500ml per day was shown to offer protection against age-related cataracts. A specific clinical trial revealed that diabetic people who regularly consumed green tea for one year had a 50% risk reduction of diabetic retinopathy than those who did not consume green tea.
Studies showed that eye tear film quality in normal eye subjects appeared to reduce after just one acute dose of green tea consumption. As a topical treatment, green tea was proven to be a safe and effective treatment for evaporative dry eyes and Meibomian Gland Dysfunction (MGD).
Summary: Green tea catechin constituents have displayed considerable efficacy in preventing and treating eye-related disorders that can otherwise cause severe complications including blindness.
The Risks and Side-Effects of Green Tea
Consumption of green tea is generally considered extremely healthy and safe. There are rare, minimal side-effects reported from the use of green tea. Still, overconsumption of green tea can pose health risks due to its caffeine content and traces of aluminum.
Caffeine is an active and natural stimulant. Though green tea has a lower caffeine content (between 25 – 40 milligrams per 8 ounces), people sensitive to caffeine should avoid or exercise caution in the consumption of green tea. Caffeine sensitivity can cause insomnia, nausea, upset stomach, mental anxiety, headaches, irritability, tremors, and more.
Pregnant women should avoid or reduce green tea consumption to one or two cups to prevent miscarriages and growth retardations. Caffeine’s diuretic effects can be harmful to those with kidney problems especially those prone to or with renal failure.
Green tea consumption is best avoided for those with heart conditions or cardiovascular diseases as it can interfere with the heart-rate. Individuals under prescribed medications such as blood thinners, hypertension drugs, stimulants such as amphetamines, etc. should avoid green tea. Persons under medication for anxiety, depression, etc. should consult a doctor before the intake of green tea.
The Final Note
Green tea has been used by traditional Chinese and Japanese as a nutritional beverage that could provide various benefits to living a healthy life. Science has proved that green tea with its powerful catechins, amino acids, vitamins, minerals, and pigment constituents, can indeed be beneficial in reducing weight, fighting cancer, preventing cardiovascular risks, treating inflammatory diseases, and supporting good bone and eye health.
Though green tea consumption is relatively safe, pregnant women and certain individuals using prescribed medications or with sensitivity to caffeine, kidney problems, and cardiovascular diseases should exercise caution consuming green tea. Regular green tea consumption can not only refresh the body and mind but also bestow multiple health benefits for overall physical and mental wellbeing.