Green tea is one of the most widely consumed beverages in the world, with origins tracing back thousands of years to ancient China. Made from the leaves of the Camellia sinensis plant, green tea is processed and manufactured in a way that prevents the leaves from oxidizing and allows them to maintain their distinctive green color. This also preserves many of the inherent nutrients and antioxidants found in the tea leaves.
In recent decades, modern scientific research has revealed and confirmed many different health benefits of regularly drinking high-quality green tea. The leaves used to make green tea contain various antioxidant compounds called catechins, including one known as EGCG, which is a very powerful antioxidant. These catechins boost metabolism, improve brain function, and may even help protect against serious diseases like cancer.
This blog post will provide a comprehensive overview of everything you need to know about green tea. First, we’ll take a deep dive into the long and storied history of green tea, tracing its origins in ancient China and how it spread from there to Japan and eventually to the rest of the world through global trade. Next, we’ll look closely at how green tea is harvested and processed to maintain its characteristic green leaves. We’ll also summarize the chemical composition and ingredients that give green tea its unique nutritional profile. Finally, we’ll walk through decades of scientific research on green tea and its associated health benefits for both body and mind.
The Ancient Origins and History of Green Tea
According to ancient Chinese legend, the history of tea began in the year 2737 BC when some leaves from a wild tea bush accidentally fell into a pot of boiling water being heated by the Chinese Emperor Shennong. The Emperor enjoyed drinking the resulting tea-infused water so much that he is considered the father of Chinese tea culture.
For several thousand years after this legendary event, tea was consumed primarily in China and largely remained a regional beverage. Tea leaves were prepared by methods like steaming or pan-frying to deactivate certain enzymes and limit oxidation, creating green and oolong teas. Tea was commonly boiled in pots and consumed for its medicinal properties as well as for refreshment.
The consumption and production of tea grew over the centuries throughout China until it became a widely popular drink across all levels of society by the 8th century AD. In the late 8th century, a famous Chinese poet named Lu Yu wrote the first definitive book about tea, the Ch’a Ching. This seminal book codified the ritual preparation and consumption of tea into an art form and cemented tea’s cultural importance in China.
Around the early 9th century AD, tea spread beyond China for the first time as Japanese Buddhist monks who had traveled to China brought back tea seeds and a knowledge of tea preparation and culture. As tea drinking in Japan grew in popularity through the 1200s, the traditional Japanese tea ceremony also developed as a form of spiritual refinement. The detailed ceremonial process provided tranquility and contemplative stillness for the mind.
For centuries, green tea remained largely unknown outside of east Asia. It wasn’t until the early 17th century when global trade began to spread between Europe and east Asia that green tea was first introduced to the Western world. Portuguese priests and merchants who had settled in Japan brought green tea back to Europe as gifts. At first, it was so rare and expensive that only the elite could afford to buy it.
The Dutch East India Company eventually imported the first shipment of green tea to Europe from China in 1610. At first it was mainly sold in coffee houses, but its popularity grew steadily. By the mid-1700s, green tea had become a widely popular beverage in Western countries among all classes of society, though still far less than in China and Japan where tea drinking had been entrenched for thousands of years.
The Growth of Tea in the 19th and 20th Centuries
In the 19th century, the Chinese tea trade grew rapidly and teas began to be exported in large quantities to Western countries. To meet this growing demand, tea cultivation spread across China from the southeast coastal regions further inland and into Yunnan province in the southwest. More efficient methods of growing and harvesting tea were developed to increase yields.
Great Britain, as a major colonial power in east Asia at the time, became enamored with Chinese tea culture. The British introduced tea farming into India in an effort to break China’s global monopoly on tea production. However, since India lacked natural camellia sinensis plants, this early attempt failed until hybrids were created using seeds from China and Japan. By the early 1900s, India had become a major tea producer, especially of black teas.
Although black teas surpassed green teas in popularity in the West up until the 20th century, green teas were still regularly imported from China and Japan. Green tea saw a major resurgence starting in the 1990s and 2000s as research began to demonstrate its unique health benefits compared to black tea. Celebrities and pop culture figures endorsing the benefits of green tea also fueled its renewed popularity.
Green tea is now one of the most popular beverages consumed daily across the world, though China and Japan still remain the top producers and per capita consumers. Countries as diverse as India, Sri Lanka, Kenya, Indonesia, and even the United States now produce green tea to meet rising global demand. The ancient beverage has become a globalized commodity while also retaining its cultural significance in east Asia.
Green Tea Processing and Manufacturing
Now that we’ve traced the long and influential history of green tea, let’s look at how green tea is harvested and processed after harvest to create the finished tea products.
All tea varieties, including green, black, oolong, and white tea, come from the leaves of the shrub species Camellia sinensis. What makes green tea unique is how the tea leaves are processed shortly after being picked, which is different from how other true teas are prepared.
The very first step in making any tea is plucking and harvesting the youngest tea leaves, which produce the best flavor. For high-quality green teas, only the unopened leaf buds and top two youngest leaves are picked, usually by hand. Lower quality tea may be machine harvested which can bruise leaves.
After harvesting, the tea leaves are withered, meaning some of their moisture content is reduced prior to further processing. Withering originally involved simply air-drying the leaves in sunlight, but today producers use carefully controlled indoor methods. Leaves might be set out on racks or troughs to gently reduce moisture over several hours. This softens the leaves to prepare for shaping.
The next step is the defining process that differentiates green teas from other varieties. For green tea, the leaves undergo minimal processing and very little oxidation. This preserves the chlorophyll in the leaves to maintain the characteristic green color. Traditional methods involve pan-firing or steaming the leaves.
Pan-firing involves manually rolling the leaves into balls that are then heated in pans over fires or furnaces. The leaves are fired at hot temperatures for a very brief time, stopping the oxidation process but retaining greenness.
Steaming involves suspending the leaves over boiling water in steamers. The leaves are steamed for less than a minute, which similarly halts oxidation and preserves the green color. Steaming is more common in Japanese green tea processing.
After this heating process, the leaves may be shaped through additional rolling or forming steps. The leaves are then dried completely using hot air rather than being fermented or further oxidized. The drying process ensures the leaves are preserved for safe long-term storage.
The dried green tea leaves are then sorted into grades and packages based on factors like leaf size, shape, and quality. Lower grades typically end up in tea bags, while delicate whole leaves are reserved for loose leaf tea. Unlike black teas, high-end green teas are made from a single type of plant cultivar rather than a blend. This provides distinctive and delicate flavor.
The resulting minimally processed leaves have only been very lightly oxidized, usually less than 10%. This oxidation arresting is what gives green tea its unique flavor and health promoting properties compared to more heavily oxidized black or oolong tea leaves.
The Unique Chemical Composition of Green Tea
In the first part of this blog series, we traced the origins and history of green tea and how it is harvested and processed. Now let’s take an in-depth look at the chemical composition of green tea leaves that gives this beverage its distinct nutritional profile.
Catechins – The Powerful Antioxidants
Green tea contains a class of antioxidants called catechins, which make up 15-30% of the dry weight of the leaves. The most abundant and important catechin found in green tea is EGCG (epigallocatechin gallate).
EGCG is considered a very potent antioxidant. Antioxidants help protect against cell damage caused by free radicals, which are unstable molecules generated by normal metabolic processes in the body. Over time, excessive free radical formation can contribute to chronic diseases. Research shows that the EGCG in green tea has anti-cancer effects by neutralizing free radicals before they can damage cells.
Other catechins found in green tea include epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and gallocatechin gallate (GCG). Each catechin has unique properties and synergistic effects when working together as antioxidants.
Flavonoids – The Pigments with Health Benefits
Flavonoids are a broad class of plant pigments that give many fruits, vegetables and teas their vivid colors. In green tea, flavonoids provide the yellow, orange and reddish hues seen in the leaves.
These flavonoids act as antioxidants within the body to help neutralize those damaging free radicals. Two major flavonoids found in green tea are kaempferol and quercetin.
Kaempferol gives green tea some of its light yellowish color. Research indicates kaempferol has anti-inflammatory, anticancer, cardioprotective, and neuroprotective effects in the body.
Quercetin is responsible for some of the reddish color in green tea leaves. It acts as an antihistamine and anti-inflammatory compound. Quercetin may help reduce risk factors for heart disease like high cholesterol and hypertension.
Theanine – The Relaxing Amino Acid
Theanine is a unique amino acid found almost exclusively in the Camellia sinensis tea plant. It is responsible for the relaxing, calming effect felt when drinking green tea, despite the presence of caffeine.
Theanine promotes relaxation and stress reduction by increasing alpha brain wave activity. It also boosts levels of serotonin and dopamine in the brain which improves mood. The combination of theanine and caffeine in green tea provides both a relaxed and focused feeling.
Theanine makes up about 2% of the dry weight of green tea leaves. The amount in a single cup of green tea varies from 20-60 mg. Supplements are also available in higher isolated doses.
Caffeine – The Light Stimulant
While green tea contains far less caffeine than coffee or energy drinks, it still contains some caffeine which acts as a mild stimulant. Caffeine content in green tea ranges from around 20-45 mg per 8 oz cup.
Caffeine works by blocking adenosine receptors in the brain which promotes increased focus and alertness. Green tea’s low caffeine content provides gentle stimulation without causing excess jitteriness or energy crashes.
The caffeine and theanine in green tea work synergistically together. Theanine helps counter the anxious side effects of too much caffeine consumption. At the same time, the low caffeine levels provide clean energy without sedation.
Vitamins and Minerals
Green tea contains small amounts of essential vitamins and minerals that contribute to its overall nutritional value.
Vitamin C is found in green tea, which boosts immunity and acts as an antioxidant to protect cells from damage. Green tea’s catechins may actually increase the absorption of vitamin C.
Green tea also provides B vitamins like thiamin, riboflavin and folic acid which help convert food into usable energy in the body. The minerals manganese and zinc act as cofactors for critical enzymatic processes.
Other trace minerals found in green tea include chromium, selenium, nickel, fluorine, magnesium, sodium and potassium. These help support bone health, blood sugar control, thyroid function, and more.
Carotenoids, Polyphenols and Other Compounds
Green tea contains other beneficial plant compounds like carotenoids, chlorophyll, polysaccharides, and polyphenols.
Carotenoids provide yellow, orange and red pigments. Green tea carotenoids like beta-carotene can be converted to vitamin A in the body. Chlorophyll lends a green color and provides anti-inflammatory activity.
Polysaccharides are complex carbohydrates that stimulate the immune system. Polyphenols have antioxidant effects that reduce oxidative damage and may inhibit tumor growth.
This diverse mix of plant-based micronutrients and phytochemicals give green tea its unique nutritional and sensory profile. Next we’ll explore how these compounds impact human health.
The Scientifically-Proven Health Benefits of Green Tea
In the first two parts of this series, we learned about the history of green tea, how it is processed, and its unique chemical composition. Now let’s explore what decades of scientific research says about the multitude of potential health benefits that regularly drinking high-quality green tea can provide.
Weight Loss and Fat Burning
Numerous studies have found that the catechins and caffeine in green tea can boost metabolism and promote fat loss, especially in the stomach area.
Green tea catechins appear to stimulate the body to burn calories and break down fat. EGCG in particular helps inhibit an enzyme that normally breaks down norepinephrine, a hormone involved in fat burning. Higher norepinephrine levels then lead to increased calorie and fat burn.
Drinking green tea before cardio exercise may also amplify fat burning effects. The combination of green tea compounds and exercise creates a synergistic effect for enhanced weight loss and body fat reduction.
Brain Health and Function
The catechins, amino acids, and vitamins in green tea provide neuroprotective effects that may improve memory, mood, and cognition.
Green tea consumption has been linked in studies to better working memory and attention span. The antioxidants in green tea may help protect the brain from oxidative damage that can impair cognition and contribute to dementia.
L-theanine promotes increased alpha brain wave activity which creates a state of relaxed focus and attention. This allows you to better concentrate on work or studies without feeling sleepy.
Green tea may also help reduce risk of neurodegenerative diseases like Alzheimer’s and Parkinson’s. The polyphenols appear to prevent the buildup of beta-amyloid plaques that lead to Alzheimer’s progression.
Cancer Prevention and Treatment
A major catechin in green tea called EGCG has been shown in lab studies to inhibit tumor cell growth and prevent metastasis. Population studies also show green tea drinkers have lower risks of certain cancers.
The catechins prevent DNA damage from free radicals that can lead to cancerous changes. They also may inhibit angiogenesis, which cuts off the blood supply that growing tumors need.
Green tea consumption is associated with lower risks of breast, prostate, colorectal, lung, liver, pancreatic, and other cancers. Matcha green tea powder may provide even greater protection due to its higher catechin content.
Green tea extract supplements are being studied as adjunct treatments alongside chemotherapy drugs. Early results suggest they may enhance cancer drugs’ effectiveness or reduce treatment side effects.
Cardiovascular and Heart Health
Habitual green tea consumption is linked to lower risks of heart disease and stroke. Green tea has been found to improve many biomarkers related to heart health.
Green tea flavonoids and catechins reduce LDL cholesterol oxidation and plaque buildup in arteries. Green tea also helps lower blood pressure and prevents hypertension.
Population studies show adults who regularly drink green tea have up to a 31% lower risk of dying from heart disease. Green tea supports healthy blood vessel function and blood circulation.
Matcha green tea in particular was found to lower triglycerides and LDL cholesterol while increasing HDL levels, providing heart-protective benefits.
Immune System Support
The antioxidants and phytochemicals in green tea provide antiviral, antibacterial, and anti-inflammatory activity to strengthen immunity.
Green tea catechins modulate the body’s immune response. They prevent excess inflammation when sick but still allow enough immune activation against infections.
In clinical trials, green tea has been found to help prevent influenza infection or reduce severity and duration of symptoms. It shows promise for protecting against COVID-19.
Blood Sugar Control and Diabetes Management
Compounds in green tea may enhance insulin activity and sensitivity. This leads to better blood sugar control.
Studies show habitual green tea drinking is associated with significantly lower risk of developing type 2 diabetes. Green tea may also help prevent diabetic kidney disease.
Matcha green tea was found to better stabilize blood sugar levels after meals compared to a placebo drink. Matcha’s synergistic mix of catechins optimizes insulin response.
Skin Health and Anti-Aging
Applying green tea topically or drinking it regularly both appear to provide anti-aging skin benefits. Green tea is being added to more cosmetic products.
Green tea polyphenols protect skin cells from sun damage by quenching free radicals before they can degrade collagen and cause wrinkles. This reduces redness and inflammation too.
Drinking green tea may enhance skin elasticity and smoothness. The EGCG in matcha green tea protects against cellular damage that leads to sagging and premature aging when applied to skin.
Green tea shows promise for treating acne, rosacea, and atopic dermatitis when used topically. The polyphenols reduce inflammation and bacterial overgrowth.
Green tea has progressed from an ancient medicinal drink to a globally popular beverage that science continues to reveal health benefits of. Compounds like EGCG have antioxidant, anti-cancer, and metabolism enhancing effects that protect the body and mind in myriad ways.
When high-quality, fresh green tea is prepared properly, it delivers a mix of catechins, amino acids, vitamins, minerals, and other plant compounds unavailable elsewhere in the diet. Drinking just a few cups of green tea per day is an easy and delicious habit that boosts overall wellness.