Beneficios do chá verde
MAIN HEALTH BENEFITS OF GREEN TEA
Powerful antioxidant
Provides strong anti-inflammatory activity
Improves cardiovascular health
Improves brain function and improves mood
Protects the brain from ageing
Stimulates weight loss and fat burning
Eases digestive symptoms and bowel disease
Reduces blood pressure and cholesterol
Helps to fight infections
Helps remove heavy metals
Assists in the treatment of cancer
Upregulates longevity genes
BOTANICAL NAME
Camellia sinensis
WHAT IS THE HISTORY OF GREEN TEA?
“Tea is a miraculous medicine for the maintenance of health. Tea has an extraordinary power to prolong life.” Eisai (‘Father of Tea’ in Japan), Maintaining Health by Drinking Tea, 1211.6
“Better to be deprived of food for three days than tea for one.” Ancient Chinese Proverb
There are many legends surrounding green tea. According to one account, tea was discovered quite accidentally by the Chinese emperor Shen Nung in 2737 B.C. The ‘Divine Healer’, as the emperor was called, routinely boiled his drinking water before consuming it and one day some leaves from a nearby tree fell into the pot producing an excellent tasting and fragrant beverage. The emperor, upon drinking the concoction, proclaimed the beverage as ‘‘heaven sent”, and as a result tea was discovered.
The cultivation of tea in Japan was initiated in the 11th century by the Zen Buddhist monks who also developed methods for processing and preparing the powdered green tea known as ‘matcha’. In Japanese ‘cha’ means tea, and ‘ma’ means powder
Historically green tea was a luxury beverage in Japan available only to court nobles, Buddhist monks and other select members of society. It was also used for medicinal purposes. Today green tea is an integral part of the Japanese diet drunk together with meals
The tropical and temperate regions of Asia, Africa and South America are considered the main origins of the tea plant, an evergreen shrub. The majority of members of the Theaceae tea family are obtained from India, Sri Lanka, China and Japan.
To produce green tea, freshly harvested leaves are immediately steamed to prevent fermentation yielding a dry, stable product. This steaming process destroys the enzymes responsible for breaking down the colour pigments in the leaves and allows the tea to maintain its green colour during the subsequent rolling and drying processes. These processes preserve natural polyphenols with respect to the health-promoting properties. As green tea is fermented to oolong and then to black tea, it loses much of it’s antioxidant properties. The polyphenol compounds (catechins) in green tea combine to form a variety of theaflavins with the result that these teas have different biological activities with green tea being the stongest. Black tea also contains up to three times the amount of caffeine as green tea.
TARGETS AND MECHANISMS OF ACTION
The chemical composition of green tea is complex. It contains polyphenols, which include flavanols, flavandiols, flavonoids and phenolic acids.
Most of the green tea polyphenols are flavonols, commonly known as catechins. There are four kinds of catechins mainly found in green tea: epicatechin (EC), epigallocatechin, epicatechin-3-gallate and epigallocatechin-3-gallate (EGCG).-
Green tea also contains proteins (15 to 20% dry weight), whose enzymes constitute an important fraction; amino acids (1 to 4% dry weight) such as theanine or 5-N-ethylglutamine, glutamic acid, tryptophan, glycine, serine, aspartic acid, tyrosine, valine, leucine, threonine, arginine and lysine; carbohydrates (5 to 7% dry weight) such as cellulose, pectin, glucose, fructose and sucrose; minerals and trace elements (5% dry weight) such as calcium, magnesium, chromium, manganese, iron, copper, zinc, molybdenum, selenium, sodium, phosphorus, cobalt, strontium, nickel, potassium, fluorine and aluminium; and trace amounts of lipids (linoleic and α-linolenic acids), sterols (stigmasterol), vitamins (B, C, E, K), xanthic bases (caffeine, theophylline), pigments (chlorophyll, carotenoids) and volatile compounds (aldehydes, alcohols, esters, lactones, hydrocarbons).
While most of the research has been conducted on the ECGC constituents of green tea, a large body of research has been done on the flavonoid portion of the plant (kaempferol, quercetin and emyricetin) as these have been shown to be strong antioxidants and found to be potent chemo- preventative phytochemicals in skin cancer.
ANTIOXIDANT AND ANTI-INFLAMMATORY ACTIVITY
Limits the amount of free radicals by binding to reactive oxygen species (ROS)
increases plasma antioxidant capacity and reduces lipid peroxidation (especially oxidation of LDL.
Significant geno-protective effects were found with an in-vitro study and human trial using biomarkers of oxidative stress
Improves antioxidant systems and activates cyclic AMP response element-binding protein(CREB) in vivo leading to neuroprotection
Protects proteins and lipids from oxidation
Increases production of IL-10 (anti-inflammatory cytokine)
Used as a protective agent in pathological disorders caused by oxidative stress in iron overload conditions
Significantly decreases serum levels of iron, ferritin and malondialdehyde
Increases total antioxidant capacity
Inhibits the redox active transport factors – nuclear factor-kappaB (NF-kB) and activator protein 1
Upregulates antioxidant enzymes – catalase, glutathione peroxidase (GPx), and superoxide dismutase (SOD)
Scavengers free radicals by decreasing superoxide anions, nitric oxide radicals, singlet oxygen, and peroxynitrite radicals
Reduces the formation of kidney stones
BONE GROWTH ACTIVITY
Prevents age related bone loss in elderly women and men. Ingestion of green tea and green tea bioactive compounds are beneficial in mitigating bone loss of this population and decreases their risk of osteoporotic hip fractures
Decreases the risk of fracture by improving bone mineral density and supporting osteoblastic activities while suppressing osteoclastic activities
ANTI-CANCER ACTIVITY
Plays an adjunctive role for ovarian, cervical, colorectal, prostate, leukaemia and breast cancers
Studies report the daily consumption of at least 10 Japanese-size cups of green tea results in delayed onset of cancer
Enhances the cancer-preventive activity of sulindac (a non-steroidal anti-inflammatory drug) and tamoxifen (a hormone therapy drug), resulting in smaller doses of these drugs and fewer adverse effects
Aromatase-inhibiting activity is more effective for women drinking green tea pre-menopause, which may delay the onset of breast cancer
Modifies oestrogen metabolism or conjugation and in this way influences breast cancer risk
Is a rich source of phytochemicals that can interact with and regulate xenobiotic metabolising enzymes
Lowers tendency for colorectal cancer development
Higher intake of green tea is linked with a reduced risk of adult leukaemia, acute lymphocytic leukaemia, chronic myeloid leukaemia and chronic lymphocytic leukaemia
Protects against development of primary hepatocellular (liver cell) carcinoma (HCC), especially in patients with chronic hepatitis
Significantly decrease the risk of ovarian cancer
Downregulates the expression of proteins involved in inflammation, cell signalling, cell motility and angiogenesis
Induces apoptosis and can potentiate the effects of cisplatin (a chemotherapeutic agent)
Endometrial cancer risk can be reduced by up to 23% for regular green tea drinkers
Human clinical trials demonstrate a decrease in the rate of tumour progression from prostate intraepithelial neoplasia to adenocarcinoma, together with evidence of a decrease in serum markers of tumour progression
Protects against nephron-toxicity by the chemotherapeutic drug cisplatin
CARDIOVASCULAR SYSTEM ACTIVITY
Shown to inhibit atherosclerosis, reduce lipid levels overall and improve the ratio of LDL to HDL
Increases high-density lipoprotein (HDL) cholesterol
Demonstrates statistically significant reductions in both systolic and diastolic blood pressure by inhibiting angiotensin-converting enzyme (ACE)
Reduces lipid peroxidation (especially oxidation of LDL)
Reduces cholesterol absorption in the intestines
Increases faecal excretion of cholesterol and fats
Reduces liver production of cholesterol and regulates LDL receptors
Improves vasodilation via increased nitric oxide regulation, increased prostacyclin and increases in cAMP and cGMP signalling pathways
ANTI-DIABETIC ACTIVITY
Reduces fasting serum glucose, insulin levels and insulin resistance
Reduces body weight and BMI and has favourable effects on body composition
Studies show moderate weight loss, reduction in waist circumference and improvement in metabolic parameters
Shows significant increases in resting metabolic rate, lean body mass and strength and significant reduction in waist circumference, body fat and triglycerides when combining green tea with resistance training (compared with placebo and resistance training only)
Consuming Chinese green tea every week for at least one year has a diabetic retinopathy risk reduction of about 50%
LIVER SUPPORT
Demonstrates hepatoprotective actions and protection against NAFLD (non-alcoholic fatty liver disease)
Improves the liver’s antioxidant capacity and down regulates serum hepcidin as well as reducing the release of apoptotic related proteins
Reduces iron overload toxicity which is associated with chronic liver diseases leading to hepatic fibrosis and subsequently cancer through oxidative stress and apoptotic pathways
Provides protection from liver damage especially in patients with Hepatitis B or C
IMMUNE ACTIVITY
Shows dramatic effects on T cell functions, including T cell activation, proliferation, differentiation and production of cytokines
Improves dysregulated T cell function with respect to different subsets of CD4(+) T cells leading to a reduction in the development of autoimmune inflammatory diseases
Antibacterial effects of tea have been demonstrated against a number of microorganisms including Staphylococcus aureus, Vibrio cholerae, Escherichia coli, Shigella spp., Salmonella spp., Bacillus spp., Klebsiella spp. and Pseudomonas aeruginosa
Antiviral effects of green tea have been demonstrated against the influenza virus, as well as against the herpes simplex virus, tobacco mosaic virus, enterovirus, rotavirus, Epstein Barr virus and HIV virus
Anti-fungal effects of tea have been reported against Candida albicans, Trichophyton mentagrophytes and Trichophyton rubrum
Antimalarial properties have been shown in vitro and strongly inhibits Plasmodium falciparum growth
Green tea kills the causal organisms of typhoid fever (Salmonella typhi) and brucellosis (Brucella melitensis)
Shows direct antimicrobial effects in vitro on Streptococcus mutans, the main cause of dental caries and it also seems to inhibit the attachment of the bacteria to oral surfaces
MICROBIOME ACTIVITY
Consumption decreases the abundance of Clostridium species and increase the abundance of the Bifidobacterium species in faecal samples
Green tea catechins produce favourable improvements in human bowel conditions, as evidenced by a reduction of faecal moisture, pH, ammonia, sulphide and oxidation-reduction potential
Demonstrates a marked improvement in colitis and inflammatory bowel diseases
Has a inhibitory effect on Helicobacter Pylori and reduces incidents of stomach ulcers
MOOD, COGNITION, BRAIN ACTIVITY
Influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI)
Confers protection against depression
Improves spatial memory during aging
Three or more cups a day shows a reduction in risk of stroke and cerebral haemorrhage by 21%
ANTI-AGEING ACTIONS
Human studies indicate that four cups of green tea daily decreases DNA damage
Effective in enhancing learning and memory in vivo indicating that it may serve useful in reversing age-related memory deficits
Controls oxidation reactions in the skin to reduce skin inflammation, photo damage, cancer and skin ageing
Regulates nitric oxide (NO) pathways and cell signalling
Regulates endothelial nicotinamide adenine dinucleotide phosphate (NADPH)
Upregulates daf-16 and skn-1 gene; the DAF-16 transcription factor, homologue of the mammalian FOXO gene. is a key modulator of stress resistance, longevity, and other important cellular functions
Shown to influence several biological processes by inhibiting telomerase, mitogen-activated protein kinase (MAPK), activator protein-1, and nuclear factor-kappaB (NF-κB)
Numerous ageing models have shown that green tea is able to extend longevity significantly under several stress conditions by postponing aging and age-related diseases
Upregulates stress-resistance-related proteins (SOD, heat shock protein(hsp)-16.2) and ageing-associated genes (DAF-16, SOD3, SKN-1)
Modulates the expression of some key genes in the insulin/IGF-1 signalling pathway
Upregulates the expression of some stress resistance associated genes, such as gst-4, hsp-16.2 and hsp-70, which are regulated downstream by the insulin/insulin-like (IIS) pathway
Shown to be effective in improving age-associated disorders such as immune-senescence, inflammation and organ functions, as well as extending lifespan in experimental animal models
Promotes restoration of Nrf2 signalling as well as PPARγ and SIRT1 levels (longevity genes)
