Camellia sinensis
In 2737 BC, the Chinese emperor Shen Nung sits under a tea tree with a cup of hot water in his hand. A leaf falls into a cup by the wind and sees that the colour, smell and taste of the water changes within 2-3 minutes. The emperor is pleased with the colour and taste that the fallen leaves give to the water. After Shenn Nung drank this and found healing, then tea began to be used as a medicine for healing.
The parts of the tea that are used for medicinal purposes are the leaves. Tea contains many active ingredients, the most important of which are: Xanthine alkaloids (caffeine, theophylline, theobromine, xanthine), tannins, flavanols and flavone glycosides, polyphenols (catechin, gallocatechin, epicatechin, epigallocatechin), phenolic acids, proanthocyanidins, free amino acids, minerals such as aluminium, manganese, fluoride and potassium.
Green tea differs from black tea in terms of the ratio of catechin compounds it contains. Green tea has a higher percentage of catechins compared to black tea. After the catechin is absorbed, it reaches the target tissues and shows anticancer activity. It fights against cancer cells by providing the opposite effect at all stages of cancer formation (proliferation, transformation, inflammation, apoptosis, metastasis and occupation stages). It shrinks the tumour.
Green tea is obtained by steaming the fresh leaves of the tea at high temperature after harvesting it. Since the oxidizing enzymes that are found intensely in tea leaves at high temperatures are inactivated, there is no colour change specific to tea and almost a green appearance is displayed. In addition, since the polyphenols and catechin in its content are not oxidized, it contains higher polyphenols and catechins than black tea. Green tea has 30-40% polyphenols, while black tea has 3-10%.
Green tea polyphenols have antioxidant, anti-inflammatory, anticarcinogenic, thermogenic, probiotic, and antimicrobial properties.
Green tea;
- Reduces the risk of atherosclerosis
- Reduces the risk of developing cardiovascular diseases
- Reduces the risk of myocardial infarction (reduction of platelet aggregation and ischemic damage)
- Increasing plasma antioxidant capacity
- It is very useful in terms of reducing serum lipid concentration.
In addition;
- Showing protection against cancer
- Reducing the incidence of oral mucosal leukoplasia
- Symptomatic treatment of mild cases of diarrhoea
- Ensuring diuresis
- Facilitating digestion
- Dysuria, oedema reducer
- Weight loss
- Functional asthenia
- Central nervous system stimulant
- Reducing headaches
- It is also very important in terms of reducing the risk of osteoporosis.
It is known that black tea, which is consumed a lot in our country, has similar effects.
Standardized preparations of tea;
- 1 cup of green tea a day for antioxidant effect
- Anti atherosclerotic effect 3-4 cups of black tea per day
- At least 1 cup of black tea per day for a reduction in the risk of myocardial infarction
- Green tea activates thermogenesis and fat oxidation. The use of capsules containing 250 mg of green tea powder 8 times a day is used to provide benefits in the treatment of obesity.
These effects of tea;
Anticarcinogenic effects:
- Catechins are effective in oral and oesophageal cancers because they are absorbed from the oral mucosa.
- The antioxidant and antiproliferative effects of the polyphenols in the tea content enable it to show anticarcinogenic effects.
- Green tea and black tea reduce the risk of cancer by inhibiting the formation of oxidized metabolites of DNA.
- Green tea prevents the development of colon cancer by changing the intestinal flora.
Effects on thermogenesis:
- Catechins activate thermogenesis due to their sympathetic activity by blocking the enzyme COTT, which is the enzyme responsible for the degradation of noradrenaline.
- Epigallocatechin gallate inhibits the production of peroxidase by blocking the deamination of monoamines in glial cells, thereby inhibiting oxidative neuronal damage.
Contraindications:
Individuals with weakened cardiovascular system, kidney diseases, thyroid hyperfunction, patients at high risk of spasm, psychic disorders (such as anxiety)
Side Effects:
At high dose (more than 10 cups per day) Nervousness, anxiety, cardiac irregularities, headache, tremor, hypertension, restlessness, insomnia, irritability, irritation of gastric mucosa, diuresis.
Alerts:
- Xanthine derivatives (caffeine, theophylline) in black tea may reduce the effect of coronary vasodilators such as dipyridamole and should not be taken together.
- Green tea in combination with sulindac and/or tamoxifen can have synergistic effects and reduce each other's side effects.
- Since green tea is a source of vitamin K, it can have an antagonist effect together with warfarin.
- Tannin-rich herbs can reduce the absorption of theophylline, a bronchodilator drug used to treat asthma.
- The tannins in tea can affect the absorption of vitamins and nutrients from the small intestine. In newborns, tannins cause the development of microcytic anaemia, as they bind iron and reduce its absorption.
- High amounts of caffeine can increase the side effects and activity of theophylline.
- It can inhibit the effect of adenosine, which is used when heart rhythms are irregular.
- Green tea increases the effect of beta-lactam group antibiotics by lowering bacterial resistance.
- Caffeine in green tea reduces the sedative effectiveness of benzodiazepine group drugs.
- In people taking beta-blockers, the caffeine in green tea may cause the dose to change because it increases blood pressure.
Chemotherapy
Green tea may increase the effectiveness of chemotherapy drugs, especially doxorubicin and tamoxifen. These results have been proven by laboratory tests, but not enough clinical research has been done on humans. On the other hand, black and green tea inhibit the effectiveness of chemotherapy drugs used in prostate cancer and the genes that show selectivity to these drugs.
Clozapine
There should be a minimum of 40 minutes between the intake of clozapine, which is an antipsychotic drug, and green tea, otherwise the effectiveness of the drug decreases
Ephedrine
Agitation, tremor, insomnia, and weight loss may occur when ephedrine and green tea are taken together.
Lithium
Green tea lowers the level of lithium in the blood.
MAO-inhibitors
In people who use MAO inhibitors, especially phenelzine and tranylcypromine, the use of green tea together may cause a hypertensive crisis due to its ability to increase blood pressure.
Oral contraceptive
Oral contraceptives can increase the stimulating effect because they prolong the stay of caffeine in the body.
Phenylpropanolamine
The combined intake of phenylpropanolamine and caffeine in green tea can cause mania and hypertension.
Use in Pregnancy & Lactation:
There are no known restrictions. However, due to the caffeine and theophylline it contains, pregnant women are advised not to consume more than 5 cups of tea a day.
Lactation:
Consumption of tea during breastfeeding can lead to sleep disturbance in the newborn.
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