trà xanh green tea thành phần hóa học và lợi ích của trà xanh đối với cơ thể

GREEN TEA Green tea comes from a tea plant native to Asia called Camellia sinensis. Black tea also comes from this same plant. What makes green tea different, and green, is not the plant used to make the tea, but how the plant is processed. Green teas are the least processed of commercial teas and the method used preserves more of the nutrients and health benefits.

GREEN TEA

Green tea comes from a tea plant native to Asia called Camellia sinensis Black tea also comes

from this same plant What makes green tea different, and green, is not the plant used to make the tea, but how the plant is processed Green teas are the least processed of commercial teas and the method used preserves more of the nutrients and health benefits

Green tea leaves are picked and then immediately fired, a tea processing term which means the

leaves are either steamed or heated The tea leaves are then dried and prepared for either sale or further processing Other teas are picked, dried by a process commonly called "withering", rolled

or broken which induces oxidation, and then dried Oxidation removes most of the necessary nutritional values from the tea and then the leaves are dried to halt oxidation Oxidized teas are called black teas and most of the tea we drink in the Western hemisphere is considered black tea Because of the process used to make black tea, most of the antioxidants that are proven to provide health benefits are removed which is why green tea, still antioxidant rich, is considered healthier Black teas have the characteristic brown color when brewed that many associate with tea Green

tea, however, has a much lighter hue and flavor due to the minimal processing.

Many people believe green tea to have curative effects Recent studies indicate that the green teas contain powerful antioxidants that do boost health and the immune system The American Cancer Society has studied the benefits of green tea to both prevent and treat cancer Other studies indicate that green tea may ward off or slow Alzheimer's disease Many believe that green teas are an effective aid in weight loss and others believe green teas offer benefits for arthritic patients

Green teas are available in leaf form, in tea bags, in nutritional supplements, and as prepared

beverages Detailed information is available from a variety of sources Check with a medical professional, an herbalist, or look in bookstores for complete information about the proven and perceived benefits of green tea

What Does A Tea Leaf Contain? –

Fresh-cut tealeaves consist of 75-80% water A variety of green tea flavors are formed through the

combination of three main taste components :

Catechin– Bitterness & Astringency

Caffeine– Bitterness

Theanine & Amino Acids– Flavor & Sweetness

Catechin –

Catechin is a tannin peculiar to green tea because the black tea fermentation process reduces catechins in black tea Catechin is a powerful, water soluable polyphenol and antioxidant that is easily oxidized

Several thousand types are available in the plant world As many as two thousand are known to have a flavon structure and are called flavonoids Catechin is one of them

Research aimed at finding the active compounds in green tea revealed that its protective effects are due chiefly to catechins Tea contains four main catechin substances: EC, ECg, EGC and EGCg, all of which are inclusively called catechin Epigallocatechin gallate (EGCG) is the most powerful

of these catechins EGCG as an antioxidant is about 25-100 times more potent than vitamins C and

E One cup of green tea provides 10-40 mg of polyphenols and has antioxidant effects greater than

a serving of broccoli, spinach, carrots, or strawberries The high antioxidant activity of green tea makes it beneficial for protecting the body from oxidative damage due to free radicals Research shows that green tea may help the arterial wall by reducing lipids Green tea can protect against experimentally induced DNA damage, and slow or halt the initiation and progression of

undesirable cell colonies Studies show evidence that green tea provides immunoprotective qualities, particularly in the case of patients undergoing radiation or chemotherapy White blood cell count appear to be maintained more effectively in patients consuming green tea compared to non-supplemented patients

According to the U.S National Cancer Institute, in laboratory studies using animals, catechins scavenged oxidants before cell damage occurred, reduced the number and size of tumors, and inhibited the growth of cancer cells White tea is said to be even more effective However, human studies have proven more contradictory, perhaps due to such factors as variances in diet,

environments, and populations Below is a list of benefits:

- Eliminates free radicals preventing cancer development by blocking the growth of substance that

causes cancer This also arrests aging

- Connects with cholesterol, absorbs and blocks it

- Decreases cholesterol level in blood and prevents bad cholesterol caused by oxidation, which prevents narrowing of blood vessel caused by the build-up of bad cholesterol

- Prevents arterial sclerosis, thrombosis, heart attacks and brain strokes

- Effective for high blood pressure

- Blocks a function of enzyme that digests and absorbs sugar and prevents diabetes.

- Suppresses aggregation of platelets and prevents thrombosis such as heart attacks and brain strokes

- Fights bacteria and viruses and prevents influenza, food poisoning and cavities including

including: O-157, Dysentery, Cholera, Mouth bacteria that can damage teeth, gums, and lead to periodontal disease, Piccoli, which causes gastric ulcers

- Improves conditions of intestines by blocking growth of bad bacteria and enhancing good

bacteria like bifid bacteria This regulates the function of intestines

- Connects with substances (breath, fish, meat, human waste, etc.) and prevents odor

- Detoxifies by connecting with poisonous substance and harmful heavy metals (lead, chrome, mercury, cadmium, etc.) and dissolves it

- Changes harmful ultraviolet rays into non-harmful light in a plant to protect it

- Gargling with green tea is believed to be an effective way to protect oneself from influenza because of tea’s anti-viral functions

Caffeine –

A cup of green tea contains about 15 to 30 mg of caffeine, a stimulant affecting the central nervous system It is an important quality in green tea providing some of its astringency

Japanese people drink green tea to soothe hangovers and this is because the caffeine in green tea encourages metabolization of alcohol On a side note: it is said that the habit of drinking green tea

started in Japanese history from its refreshing effects caused by caffeine.

Caffeine is widely know for its awakening property, and the caffeine contained in green tea is no

exception Taking in appropriate amounts of caffeine encourages brain and muscle exercise, and strengthens stamina

A cup of green tea contains about 15-30mg of caffeine, normally enough to produce the stimulant

effects typically associated with caffeine However, because green tea also contains theanine, caffeine effects are counteracted and little if any stimulation actually occurs The

caffeine-counteraction effect of theanine is being further researched Theanine is a very important relaxing component unique to green tea

Health Benefit:

Typically associated as a stimulant effecting central nervous system and mental alertness Prevents sleepiness and speeds recovery from fatigue Caffeine also enhances athletic ability and endurance When caffeine is taken together with exercise, subcutaneous fat (paniculus adiposus) is

metabolized as an energy source rather than depleting glycogen stores, leading to increased

stamina In addition, caffeine is considered a good remedy for hangovers because caffeine blocks absorption of alcohol and enhances its metabolization Has a diuretic function (enhances

urination), which encourages detoxification and the discharge of body wastes and natrium (Na) that raises blood pressure Activates blood circulation

Amino Acid (L-Theanine: Caffeine Counteraction) –

Theanine is an amino acid found in tea that produces a calming effect on the brain (Yokogoshi et

al 1998b) There are about 20 different types of amino acids in tea More than 60% of these amino acids consist of theanine, which is unique to green tea because the steaming process does not eliminate it Theanine has a similar structure to glutamine providing an elegant taste and sweetness

in green tea L-theanine is a healthy amino acid that is only found in tea plants and certain

mushrooms

Health Benefit:

Theanine also helps to protect nerve cells in the brain, lengthening the life of these cells It is linked to increased alpha brain wave production and is considered a natural antidepressant and stress reliever Japanese studies link consumption of L-theanine with strengthening the immune system L-theanine is often added to energy drinks and is known to give a 6-hour sustainable energy boost

Theanine easily crosses the blood-brain barrier and exerts subtle changes in biochemistry that cause a tranquilizing effect The production of GABA, the brain chemical known for its calming effect, is increased after taking theanine Increased GABA can also put you in a better mood and create a sense of well-being Dopamine, another brain chemical with mood-enhancing properties is also increased by theanine

Green tea contains a much higher concentration of theanine than other teas Theanine has been

proven to lower blood pressure It works through its GABA enhancing effects Along with its calming effect on the brain, GABA also lowers blood pressure

Amino Acid (Butyric Acid) -

Amino Butyric Acid (GABA) is produced if tealeaves are left without oxygen Regular crude tea processing produces a tea with GABA

Health Benefit:

Suppresses high blood pressure

Vitamin A (Carotene) –

Several types of carotene exist in tea leaves ß-carotene is the most prevalent (22mg%) ß-Carotene converts to Vitamin A once absorbed in the body Carotene content is high in quality teas

Health Benefit:

Promotes better vision Among the carotene types, ß-carotene particularly has strong antioxidant effects, eliminating free radicals Antioxidant effects help prevent aging and cancer

Vitamin B1 - Thiamine –

This vitamin is necessary for proper metabolism of sugar, particularly essential for Asians, whose primary nutrition comes from rice Amount per 100 g of tea: 600 µg in Matcha

Health Benefit:

Known to speed recovery from fatigue

Vitamin B2 - Riboflavin

Necessary for red blood cell formation, antibody production, and cell respiration and growth This vitamin also helps tissues of the skin, hair, nails, and hair utilize oxygen more efficiently

Health Benefit:

Maintains proper skin condition (Prevents rough skin) and enhances growth Promotes cell growth and the production of antibodies

Vitamin B3 - Niacin

Important for the release of energy from carbohydrates and fats, the metabolism of proteins, making certain hormones, and assisting in the formation of red blood cells It also imrpoves the blood cholesterol profile

Health Benefit:

Maintains proper skin condition, lowers cholesterol Currently being researched for helping to prevent and control diabetes

Vitamin C

Necessary for collagen growth, the substance that connects cells Sencha contains significant amounts of Vitamin C (250mg per 100g of tea) Fermented teas (black, oolong tea) contain far less because vitamin C dissolves in the fermentation process

Health Benefit:

Antioxidant vitamin that eliminates free radicals preventing cancer and aging

Antiviral/antibacterial function assists in preventing colds Collagen growth factor cleanses skin

Vitamin E - Tocopherol

This vitamin is an antioxidant known as a tocopherol Green teas grown in non-shaded

environments contain more Vitamin E than teas grown in shaded environments

Health Benefit:

Antioxidant through fat eliminating free radicals Combats infertility Prevents aging Important in the prevention of cardiovascular disease and cancer pressure

Vitamin F – Fluorin

Particularly abundant in the Camellia family of plants Green tea contains 40-1900 ppm (parts per

million) of fluorin Mature leaves contain more fluorine than young buds, and Bancha, made from

mature leaves contains a lot of fluorine

Health Benefit:

Flourine adheres to the surface of the teeth producing an antioxidant coating this helps prevent cavities

Vitamin K - Koagulations

Vitamin K occurs in many vegetables Vitamin K is abundant in leafy greens.Dried green tea leaves have a very high concentration of vitamin K, but a cup of brewed green provides only a small amount, 0.03 mcg per 3.5 fluid ounces (roughly half a cup)

Health Benefit:

Vitamin K, an essential nutrient necessary for blood clotting

Vitamin P - Flavonoids

A type of flavonoid known as rutin The amount of Vitamin P in spring for first flush tea is lower 340mg per 100g while the summer tea content is higher 415mg per 100g Bancha, in particular, contains a high level of Vitamin P

Health Benefit:

Strengthens the walls of capillary blood vessels, helps to fight high blood pressure

Vitamin U

In higher quality teas, when dissolved, this vitamin generates a peculiar aroma like dried seaweed Gyokuro contains as much as 25mg per 100g and high-quality Sencha contains 10mg per 100g Regular quality teas and Bancha contain very little of this vitamin

Health Benefit:

Effective in fighting gastric ulcers Also used as the main substance in digestive medicines

Chlorophyll

Plays a vital role in photosynthesis Its molecular structure is similar to hemoglobin contained in human red blood cells If green tea is grown with a covering over it, chlorophyll tends to increase

as the tea leaves attempt to absorb as much light as possible This is why Gyokuro and Kabusecha (shaded teas) which contain much chlorophyll are deep green Chlorophyll does not dissolve in water and doesn't affect the color of tea liquor

Health Benefit:

Helps prevent odor and bad breath Assists in blood production Fights tumors

Minerals (Ash Content)

Green tea contains 5-7% minerals (ash content) Major types of minerals are kalium, calcium,

zinc, phosphorus, manganese, & copper Zinc and copper are necessary elements to form

antioxidants

Pectin

A natural food fiber The content level in green tea is not high, but it gives stickiness to the liquid and adds body to brewed tea

Saccharides

Tea leaves photosynthesize and produce glucose, which converts to starch and provides cellulose leaf structure These substances are called saccharides Tea leaves photosynthesize and produce glucose, which converts to starch and provides cellulose leaf structure These substances are called saccharides The amount of saccharides is lower in young buds that have not yet photosynthesized, but increase as tea leaves mature High-end teas contain fewer saccharides than low-end Cellulose does not dissolve in water and has no effect on tea taste Glucose, fructose, and sucrose do dissolve

in water but their content in tea liquor is extremely low

Saponin

Saponin is the component that causes the formation of bubbles in teas such as Matcha Research

indicates the following effects: anti-mold, anti-inflammation, anti- allergy, anti-hypertension, and anti-obesity