Last Updated June 13th, 2021
Green tea: A story of humble beginnings
Tea is one of the most popular beverages among people from ancient times until the present day, which is consumed worldwide. The source of green tea is from the plant Camellia sinensis. Various positive health benefits on human health have been observed with the consumption of green tea.
The first green tea was exported from India to Japan during the 17th century. It is estimated that about 2.5 million tons of tea leaves are produced each year throughout the world, with 20% produced as green tea, which is mainly consumed in Asia, parts of North Africa, United States, and Europe.
To produce green tea, freshly harvested leaves are immediately steamed to prevent fermentation, yielding a dry, stable product. The process of steaming destroys the enzymes responsible for breaking down the color pigments in the leaves and allows the tea to maintain its green color during the subsequent rolling and drying processes.
These processes preserve natural polyphenols (naturally occurring micronutrients in plants) with respect to the health-promoting properties. When green tea is fermented, Oolong and then black tea can be produced.
The chemical composition of green tea consists of proteins (15% to 20% dry weight), carbohydrates (5-7% dry weight) minerals and trace elements (5% dry weight), and trace amounts of lipids. Fresh leaves contain around 3% to 4% of alkaloids known as methylxanthines (class of drug that is derived from the purine base xanthine). In addition, there are phenolic acids and an amino acid such as theanine present.
Green tea contains polyphenols, which include flavanols, flavandiols, flavonoids, and phenolic acids, which accounts for 30% of the dry weight. Most of the green tea polyphenols (GTPs) are flavonols, commonly known as catechins. There are four kinds of catechins mainly found in green tea namely epicatechin, epigallocatechin, epicatechin-3-gallate, and EGCG. The amount of catechins also varies in the original tea leaves due to differences in variety, origin, and growing conditions.
Several studies have proven that these catechins have immense potential of warding off chronic inflammation and even the toxic side-effects of known carcinogens. EGCG present in green tea is known to successfully act against a number of inflammatory and cancer-causing agents. Recent studies now reveal that green tea extract can be effectively used to reduce chronic inflammation and also reduce the risk of cancer, especially in the cervical region.
The preparation of fresh green tea cannot totally extract catechins from the leaves and therefore, the concentration differs from the absolute values determined through the complete extraction of leaves. Products derived from green tea are mainly extracts of green tea in liquid or powder form.
Why should you include green tea in your daily routine?
There are numerous health benefits of green tea and can be considered as the healthiest beverage among others. Green tea is rich in antioxidants and nutrients, which can play a vital role to keep our body healthy namely improved brain function, fat loss, lower the risk of cancer, lower cardiac risk factor by reducing the blood pressure and many more.
Rich in Bioactive Compounds
Green tea contains large amounts of important nutrients namely polyphenols, which have beneficial in reducing inflammation and helping to fight cancer. Green tea contains around 30% of polyphenols including large amounts of catechin called EGCG.
Catechins are natural antioxidants that help prevent cell damage. Catechins can reduce the formation of free radicals in the body, protecting cells and molecules from damage. EGCG (Epigallocatechin Gallate), which is one of the most powerful compounds in green tea, which is helpful to treat various diseases and has powerful medicinal properties.
Improves Brain Function
An active ingredient in green is caffeine, which is a known stimulant. It is not found in large amounts but is enough to produce a response without causing any side effect as compared to other beverages such as coffee or other caffeinated drinks. Caffeine blocks an inhibitory neurotransmitter called Adenosine in the brain, which increases the firing of neurons and the concentration of neurotransmitters like dopamine and norepinephrine.
Due to this property, the brain is able to function better with improved mood, vigilance, reaction time, and memory. Another component of green tea is the amino acid called as L-theanine, which is able to cross the blood-brain barrier. L-theanine has the ability to increase the activity of the inhibitory neurotransmitter called as GABA, which can help to treat anxiety.
The combination of L-theanine and caffeine has the ability to improve brain function. It can give a soothing effect to the brain without causing drowsiness. People usually have stable energy and tend to be more productive after the consumption of green tea.
Helps in Burning Fat
The processes of converting food and liquid into usable energy are known as metabolism. Green tea contains caffeine and flavonols called as catechin, which is an antioxidant. Both of these compounds can speed up metabolism. Catechin has the ability to break down excess fat, which in turn helps in losing weight.
Caffeine present in green tea has the ability to mobilize the fatty acids from the fat tissues, which are then available to use as energy.
Acts as an Antioxidant
An ingredient in green tea called as flavonols is an antioxidant. Antioxidant clean out free radicals in the body that contribute to organ or tissue breakdown, inflammation, degeneration, and help reduce the effects of aging.
The antioxidant can also be helpful to protect against liver damage and heal ulcers. L-theanine present in green tea is a strong antioxidant, which is one of the most potent nutrients to help shield against the vast majority of chronic and degenerative diseases including cancer.
Since antioxidants keep out free radicals from the body and its systems, it can also be one of the ways to limit the growth of cancer cells and proliferate. L-theanine can particularly target cancerous cells inhibiting the growth of cancer cells and help fight cancers such as lung cancer, breast cancer, prostate cancer, and colorectal cancer.
Protects Brain in Old Age
As we know that green tea can improve brain function in short term, it is also proven that it can protect our brain in old age. Alzheimer’s disease is the most common neurodegenerative disease in humans and a leading cause of dementia. Parkinson disease is the second most common neurodegenerative disease and involves the death of dopamine-producing neurons in the brain.
Catechin compounds in green tea have various protective effects on neurons, which potentially lowers the risk of Alzheimer disease and Parkinson disease.
Lowers the risk of Diabetes Mellitus Type 2
Type 2 diabetes affects around 400 million people worldwide. It involves having elevated blood sugar levels due to insulin resistance or an inability to produce insulin. Green tea can be very beneficial in regulating insulin and reduce blood sugar levels. Studies have shown that people drinking green tea had a 42% lower risk of developing type 2 diabetes.
Reduces Cardiovascular Risk Factors
Cardiovascular risk factors include coronary artery disease (disease in the heart’s major blood vessels), high blood pressure, cardiac arrest (Sudden, unexpected loss of heart function, breathing and consciousness), congestive heart failure (chronic condition in which the heart does not pump blood as well as it should), arrhythmia (Improper beating of the heart), peripheral artery disease (circulatory condition in which narrowed blood vessels reduce blood flow to the limbs), stroke (Damage to the brain from interruption of its blood supply).
Some of the components affecting cardiovascular risk factors include total cholesterol, LDL cholesterol, and triglycerides. Since green tea has an antioxidant effect, it increases the antioxidant capacity of the blood, which protects the LDL particles from oxidation and lowers the total and LDL cholesterol, which in turn reduces the risk of heart disease.
Boosts the Immune System
Due to the antioxidant effects of green tea, it can help enhance immunity. This property can be helpful to people suffering from immune-related issues like rheumatoid arthritis, and keep the immune system strong against common cold and flu.
Acts as Antifungal
Catechins present in green tea helps in fighting against Candida albicans (opportunistic pathogenic yeast). A combination of catechins and lower doses of antimycotics (compounds that inhibit the growth of fungi) help to avoid the side effects of antimycotics.
Helps in the absorption of minerals
Flavonoid namely the catechins help in the absorption of important minerals. Green tea catechins have the potential to affect the absorption and metabolism of ions because flavonoids interact with a variety of metal ions. Iron is one of the important mineral required by the human body and catechins help in the absorption of iron, which can help in treating iron deficiency anemia.
Reduce Anxiety and Stress
Anxiety can be defined as a state of apprehension, uncertainty, and fear resulting from the anticipation of a realistic or fantasized event or situation, which impairs physical and psychological functioning.
There are many types of anxiety disorders including generalized anxiety disorder (GAD), social anxiety disorder (SAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and phobias. Anxiety, in turn, leads to stress including mental and physical stress.
L-theanine present in green tea has a close resemblance to the brain-signal chemical called as glutamate. L-theanine produces the opposite effect in the brain whereas glutamate is the brain’s most important excitatory neurotransmitter.
L-theanine binds to the same brain cell receptors and blocks them. This action produces inhibitory effects on the brain overactivity and has a calming, relaxing effect in which anxiety minimizes. In addition to blocking excitatory stimuli at glutamate receptors in the brain, L-theanine also stimulates the production of the inhibitory, relaxing neurotransmitter, which adds to the calming, anti-anxiety effect. Unlike other prescription anti-anxiety drugs, which produce sleepiness, L-theanine produces its anti-anxiety effects without producing sleepiness or impairing motor behavior.
L-theanine prevents the sudden rise in blood pressure that people experience under stress. Maintaining normal blood pressure is critical because many people have normal blood pressure readings at rest and may have a dangerously high level when subjected to stressful situations. This sudden rise in blood pressure may lead to massive arterial damage.
L-theanine influences expression of genes in brain areas responsible for fear and aggression (amygdala) and memory (hippocampus), helping to balance the behavioral responses to stress, and potentially improve conditions such as mood disorders, post-traumatic stress disorder (PTSD), and substance dependence.
Varieties of Green Tea
- Sencha: It is the most frequently drunk and well-known variety of green tea. It is made according to the most common processing methods, whereby the leaves are steamed and rolled to produce crude tea.
- Fukamushi Sencha: Green tea that has been steamed approximately twice as long as regular Sencha is called either Fukamushi Sencha or Fukamushi Ryokucha. Since the leaves have been steamed for a long time, they become finer and the tea made from these leaves has a high leaf content. A unique characteristic of Fukamushi Sencha is that many active components of the tea can be absorbed into the body even though they do not dissolve in water.
- Gyokuro: Gyokuro tea bushes are covered with cloth or reed screen (covered culture) approximately 20 days prior to picking. By limiting the amount of light that reaches the new shoots while they are growing, the generation of catechins from amino acids (theanine) is suppressed, resulting in lower astringency and a rich flavor.
- Kabusecha: For approximately one week prior to picking, Kabusecha bushes have reed screen or cloth placed over them to block out most sunlight. This enables new leaf shoots to grow without sunlight, giving the tea a darker green color, full-bodied flavor and lower astringency than Sencha.
- Matcha: Tencha that is stoneground immediately before shipping is called Matcha. A unique feature of Matcha is that it is fully consumed.
- Tencha: This tea is mainly used as the ingredient for Matcha. Tencha is grown according to the covered culture method whereby the tea bushes have reed screen or cloth placed over them to block out most sunlight. After steaming, the leaves are dried without being rolled. After removing stalks and leaf veins, the tea leaf flecks become Tencha.
- Genmaicha: It derives its name from the Japanese word brown rice, which is rice that still retains the bran covering of the rice grain. The soaked and steamed brown rice is roasted and popped and is mixed with Sencha or other tea in a ratio of approximately 50:50. One may enjoy the combination of the savoriness of roasted brown rice and the refreshing flavor of Sencha.
- Hojicha: Hojicha is made by roasting Sencha or other types of green tea, which gives it a distinctive roasted aroma. The tea leaves are roasted in a roasting pan at a temperature of approximately 200 degrees C and then immediately cooled.
- Shincha: Shincha is the new tea or first picking of the season. Picking begins in temperate regions and gradually moves northward. Shincha and Ichibancha are essentially the same tea, with the difference being in name only. Shincha’s key characteristic is its refreshing and invigorating scent of new leaves. Another feature of Shincha is its low catechin and caffeine content, making it less bitter and astringent compared with Nibancha or Sanbancha.
- Ichibancha, Nibancha, Sanbancha: Ichibancha is the first picking of new leaf shoots of the year. After that, tea is called Nibancha and Sanbancha based on the order in which it is picked. Ichibancha is sometimes called Shincha
Green tea is rich in nutrients and antioxidants making it the ideal beverage for a healthy life. Green tea is not harmful, and it has been used for centuries. It may be a useful addition to a healthy diet and exercise regime for weight loss and overall health. It can be concluded that when consumed in moderation, green tea is safe for most people.
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