What is matcha tea
Matcha is finely ground powder also called fine powdered tea of specially grown and processed green tea [Camellia sinensis] leaves 1). Matcha tea is special in two aspects of farming and processing: the green tea plants for matcha are shade-grown for about three weeks before harvest and the stems and veins are removed in processing. During shaded growth, the plant Camellia sinensis slows down growth, stimulates an increase in chlorophyll levels, turns the leaves a darker shade of green, and causes the production of amino acids, in particular theanine and produces more caffeine. The powdered form of matcha is consumed differently from tea leaves or tea bags, and is dissolved in a liquid, typically water or milk.
In rats, caffeine-induced sleep disturbances were partially counteracted by theanine 2). Theanine (l-theanine, N-ethyl-l-glutamine) is the major amino acid in tea leaves (Camellia sinensis L.), and has significant anti-stress effects on animals and humans 3). In tea leaves, other amino acids such as arginine (Arg), glutamic acid (Glu) and glutamine (Gln) are also contained. Scientists recently noted that arginine (Arg) has a significant anti-stress effect, similar to theanine, while glutamic acid (Glu) and glutamine (Gln) have no anti-stress effect 4). Scientists also found that theanine [1/5 (w/w) of caffeine] and Arg [1/10 (w/w) of caffeine] cooperatively abolished the effect of caffeine on the adrenal hypertrophy of psychosocially stressed mice 5). On the other hand, catechins, mainly epigallocatechin-3-gallate (EGCG), have potent antioxidative and anti-inflammatory activities that fortify the beneficial effect of green tea on health 6). However, epigallocatechin-3-gallate potently suppressed the anti-stress effect of theanine, while epigallocatechin (EGC), the second most abundant gallate-free catechin, retained the effect of theanine 7). These results suggest that balances among theanine, caffeine, catechins and arginine (Arg) are crucial for the function of green tea. Since the concentrations of caffeine, catechins and amino acids eluted into water are altered by the kind of tea leaves and water temperature, their content in each green tea solution needs to be measured.
The traditional Japanese tea ceremony centers on the preparation, serving, and drinking of matcha as hot tea and embodies a meditative spiritual style. In modern times, matcha also has come to be used to flavor and dye foods such as mochi and soba noodles, green tea ice cream, matcha lattes, and a variety of Japanese wagashi confectionery. Often, the former is referred to as ceremonial-grade matcha, meaning that the matcha powder is good enough for tea ceremony. The latter is referred to as culinary-grade matcha, but there is no standard industry definition or requirements for either.
Blends of matcha are given poetic names known as chamei (“tea names”) either by the producing plantation, shop, or creator of the blend, or, by the grand master of a particular tea tradition. When a blend is named by the grand master of a tea ceremony lineage, it becomes known as the master’s konomi, or a Butcher block of Leaf.
Figure 1. Matcha green tea powder
Matcha vs green tea
Green tea is produced from fresh leaves of Camellia sinensis by steaming or drying without fermenting 8). On the other hand, matcha tea powder appears brighter green than ordinary green tea, which can look brown and dull due to green tea processing. Matcha powder is a fine, velvety powder that feels smooth to the touch, like talc. Green tea feels gritty, like crushed-up leaves. In loose green tea leaf, the leaves are discarded after steeping, but Matcha dissolves completely and is fully ingested.
Matcha green tea benefits
The vibrant color of matcha tea comes from the high levels of chlorophyll, a powerful polyphenol. Polyphenols mainly composed of catechins are the main functional extracts from green tea 9) and the major green tea polyphenol is (−)-epigallocatechin-3-gallate (EGCG) accounting for more than 50% of total polyphenols 10). Polyphenols in green tea are thought to be responsible for the cancer preventive effects observed in laboratory and epidemiological studies. Daily intake of polyphenols from green tea is high in some countries. Roughly 34 % of the total polyphenol consumption from beverages in Japan comes from green tea 11).
The green tea phenolic compounds of highest concentration are gallic acid (GA), (–)-gallocatechin (GC), (+)-catechin (C), (–)-epicatechin (EC), (–)-epigallocatechin (EGC), (–)-epicatechin gallate (ECG), (–)-epigallocatechin gallate (EGCG), p-coumaroylquinic acid (CA), and (–)-gallocatechin-3-gallate (GCG) (Figure 2), with EGCG being the most abundant by weight 12). Green tea also contains condensed and hydrolyzable tannins 13). Green tea has the highest concentration of polyphenols compared to other teas, including EGCG, which may be why green tea can induce apoptotic cell death in cancer better than other teas 14).
Figure 2. Chemical structures of the major green tea polyphenols
Note: Structures shown: (1) Gallic acid, (2) (–)-gallocatechin, (3) (+)-catechin, (4) (–)-epigallocatechin, (5) (–)-epicatechin, (6) (–)-epigallocatechin gallate, (7) (–)-epicatechin gallate, (8) p-coumaroylquinic acid, and (9) (–)-gallocatechin gallate.[Source 15)]
The extraction of green tea polyphenols into tea is both time and temperature dependent 16). Tea preparation is important, as hot water preparation causes tea to be better at scavenging oxidative radicals than cold water preparations 17), which is likely due to greater extraction of polyphenols. Green tea polyphenols can act as pro-oxidants by generating hydrogen peroxide. Adding milk to green tea decreases formation of hydrogen peroxide, independent of the presence of catalase 18), which decomposes hydrogen peroxide into water and oxygen. It could be that the polyphenols in green tea bind to proteins in milk, thereby inhibiting hydrogen peroxide production. Under oxidative conditions polymerization of green tea polyphenols can also occur 19).
The evidence for the potential anti-cancer effects of green tea effects in vivo is based, in part, on epidemiological studies. For instance, an inverse association exists between tea consumption and lung cancer for smokers but not nonsmokers 20), suggesting that green tea consumption may be more important for cancer prevention in high-risk populations. This is also evident in women that are at a higher risk of breast cancer due to a genetic predisposition, where green tea, but not black tea, consumption is associated with reduced risk of breast cancer 21). Other inverse relationships that exist between green tea consumption and cancer risk include stomach cancer 22) and ovarian cancer 23). Despite these numerous studies, the role of green tea consumption in the prevention of human cancer remains unclear, in part because there is a lack of data from controlled intervention studies.
Green tea and green tea polyphenols have been shown to have anti-cancer activity in a number of laboratory studies, which could be mediated through antioxidant or pro-oxidant mechanisms. Green tea polyphenols such as epigallocatechin-3-gallate (EGCG) inhibit cell viability and induce apoptosis in a number of cancer cell lines such as osteogenic sarcoma 24), lymphoblastoid cells 25), leukemia cells 26), melanoma cells 27), T lymphocytes 28), and larynx carcinoma 29). Epigallocatechin (EGC) can inhibit breast cancer cell viability through induction of apoptosis, yet not in normal breast cells 30). Apoptosis by green tea polyphenols may occur independent of caspase-3 induction, through activation of p53 31). Evidence for cell cycle modulation also exists. Epigallocatechin-3-gallate (EGCG) in green tea causes a reduction in cell viability through G1 growth arrest in human breast cancer cells 32), which likely occurs through suppression of cyclin D1 33). Green tea polyphenols can even cause differentiation of cancer cells into slower proliferating cells 34).
Figure 3. Propose antioxidant and pro-oxidant effects of green tea polyphenols relevant to the prevention of cancer
Green tea polyphenols also have shown anti-cancer activity in vivo, yet the involvement of oxidative or antioxidative mechanisms is unclear. Green tea reduces tumor burden in a breast cancer rat model 36), and green tea polyphenols can reduce tumor burden in the forestomach of rats 37). As in the in vitro studies, Epigallocatechin-3-gallate is the primary focus for the activity behind green tea consumption. Epigallocatechin-3-gallate can inhibit cancer in animal models 38). It also can reduce inflammation in the colon, causing a decrease in oxidative and inflammatory markers in a colitis rat model 39).
A systematic review and meta-analysis by Zheng et al 40) published in 2011 suggested that green tea consumption had a borderline significant decrease of prostate cancer risk for Asian populations. In contrast, another 2 meta-analyses by Lin et al 41) and Fei et al 42) published in 2014 showed no association of green tea intake with prostate cancer. However, these meta-analyses mainly focused on the comparison of highest green tea intake with the lowest or nondrinkers. In fact, the range of green tea intake differed among these studies and the inconsistency might result from different exposure levels and variable content of major functional component epigallocatechin-3-gallate in different green tea 43).
Green tea and weight loss
Wang et al. 44) investigated the influence of tea drinking on the waist circumference, and the results were that for overweight Chinese taking green tea polyphenol (caffeine <200 mg) 458–886 mg/d for 90 d, the body fat could be decreased. A trial involving 132 overweight or obese women over 12 weeks demonstrated a significant reduction in abdominal fat and subcutaneous abdominal fat area in the group that consumed green tea compared with the control group 45). Hursel et al. 46) indicated that both treatments of a mixture of catechins and caffeine and caffeine alone could increase energy expenditure. However, only a mixture of catechins and caffeine could increase the oxidation of body fat.
In general, most studies showed that supplementation with green tea catechins led to significant decrease in body weight and body fat when compared with the baseline. A recent cross-over placebo controlled study 47) reported an increase of fat oxidation by 17% after a supplement containing various green tea polyphenols and 366 mg epigallocatechin-3-gallate [EGCG] (but not caffeine) compared with the control group. It is the first evidence that a single catechin, namely epigallocatechin-3-gallate [EGCG], has the potential to moderately affect fat oxidation. The optimal epigallocatechin-3-gallate [EGCG] dose to increase fat oxidation and support a weight management has not yet been established. The dosage of EGCG used in those studies ranged from 100 48) to 540 mg/d 49), while the duration of the studies varied from 1 day 50) to 13 weeks 51)
Some investigations on humans proved that tea drinking could alleviate metabolic syndrome, reduce the incidence of type 2 diabetes, and reduce body weight and low-density cholesterol 52). An epidemiological study conducted in Taiwan, China, showed that people with an average habitual tea consumption of 434 ml/d for more than ten years had a lower percentage of total body fat, smaller waist circumference, and decreased waist-to-hip ratio 53). Another investigation 54) conducted in USA suggested that hot tea drinking could decrease body weight and metabolic syndrome as well as the biomarker of cardiovascular disease. Researchers from Taiwan 55) reasoned that if a patient drank more than 240 ml tea every day, metabolic syndrome could be improved.
Preventing cardiovascular disease through tea drinking is another research area of interest. Potenza et al. 56) believed that tea drinking could lower blood pressure and improve endothelial functions. A Japanese study showed a potential elevation of blood triglyceride after oral administration of a corn oil emulsion (8 ml oil/kg body weight) to male mice was significantly suppressed by using Pu-erh tea extract (50 and 100 mg/kg body weight) and gallic acid (15 and 45 mg/kg body weight) 57). An epidemiological survey conducted on 76,979 people in Japan showed that the mortality induced by cardiovascular disease was decreased when more than 6 cups of tea per day was consumed 58). Research in USA and Europe demonstrated that black tea drinking could decrease the risk of cardiovascular disease 59). Another study 60) in the Netherlands involving 37,514 healthy males and females who were followed up for 13 years indicated that the mortality from cardiovascular disease was decreased by a daily consumption of 3–6 cups of black tea. It is suggested that the reduction in mortality can be attributed to the maintenance of cardiovascular health through green tea consumption 61). The majority of epidemiological studies confirmed that the cardiovascular system can benefit from tea consumption 62). However, an inverse correlation between green tea consumption and the mortality due to cardiovascular disease was also found 63). Epidemiological data suggested that black and green tea may reduce the risk of both coronary heart disease and stroke by 10%–20% 64). Oxidized low-density lipoprotein “bad” cholesterol (LDL) and hypertension are recognized as risk factors for cardiovascular disease. Pearson et al. 65) assessed the potential impact of green tea extract on LDL “bad” cholesterol oxidation and concluded that LDL “bad” cholesterol oxidation was inhibited by 3.9% after 12 h incubation with 0.08 mg/kg green tea extract. The inhibition was raised to 98% after incubation with 5 mg/kg green tea extracts. The effect of drinking green tea on developing hypertension was also evaluated in a cohort study with 1507 subjects 66). Compared with non-habitual tea drinkers, the risk of developing hypertension was cut down by 46% for those who consumed 120–599 ml/d, and it was further reduced by 65% for those who consumed 600 ml/d or more. As yet the optimal daily dose for cardiovascular health has not been established. Based on the estimation that a single cup of tea brewed with 1.5 g of green tea contains 34.5–109.5 mg epigallocatechin-3-gallate (EGCG), a daily dosage of epigallocatechin-3-gallate (EGCG) ranging from 69–657 mg (roughly equivalent to 2–6 cups of tea) appears to be beneficial to cardiovascular health 67).
The risk of developing diabetes increases with elevated grade of obesity. There have been intensive researches on the effects of natural ingredients on the prevention and treatment of diabetes. As a result of a survey on a population of 286,701, Huxley et al. 68) reported that the risk of type 2 diabetes could be lowered in those people who drank 3–4 cups of tea daily. An investigation on 17,413 Japanese of 40–65 years of age indicated that the risk of type 2 diabetes was lowered by 33% among the people who drank more than 6 cups of tea daily 69). A study from the US reported that the risk of type 2 diabetes was reduced by 30% in people who consumed 4 cups of tea daily 70). Eleven more studies concluded that catechins could reduce blood glucose or insulin level 71). However, the optimal dose of epigallocatechin-3-gallate (EGCG) for glucose control has not yet been established, though a dose range of epigallocatechin-3-gallate (EGCG) 84–386 mg/d may be adequate to support glucose homeostasis according to existing findings 72).
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