^ Jump up to: a b Johnson R, Bryant S, Huntley AL (December 2012). "Green tea and green tea catechin extracts: an overview of the clinical evidence". Maturitas (Review). 73 (4): 280–7. doi:10.1016/j.maturitas.2012.08.008. PMID 22986087. In conclusion, whilst there is a considerable body of evidence for green tea with some of it suggesting a positive effect, it is difficult to be definitive as to its health benefits.
Matcha comes in several grades that aren’t officially regulated, but the most important distinction is between ceremonial and culinary grade matcha. Ceremonial grade is made from the youngest, most tender tea leaves and is smooth and fine in texture. Use it when you’re planning to drink pure, unadulterated matcha or a top-notch latte. Culinary matcha is a less expensive and made from comparatively older leaves. It is best for baking, cooking, or making blended drinks where the matcha flavor is not imperative. (“Premium” or “select” matcha is somewhere in between the two major grades, and you can find organic versions of matcha in each category.)
In 1904, Benjamin Ginsberg ran a variety of experiments at Rondegat Farm, finally curing rooibos. He simulated the traditional Chinese method of making Keemun by fermenting the tea in barrels. The major hurdle in growing rooibos commercially was that farmers could not germinate the rooibos seeds. The seeds were hard to find and impossible to germinate commercially.
Like black and green tea, rooibos is rich in polyphenols, such as rutin and quercetin. Cell and animal studies, mostly from South Africa, have shown that rooibos extracts have antioxidant, immune-stimulating, and anti-cancer properties. But studies of rooibos tea in people are limited. There’s little or no evidence to back claims that it relieves constipation, headaches, eczema, asthma, insomnia, high blood pressure, mild depression, ulcers, diabetes, and so on.
Over a thousand years ago, matcha came to Japan as an aid to meditation practice. During long hours of sitting, monks would drink matcha to remain alert yet calm. Modern science has recently confirmed the lessons of centuries of tradition. Matcha is rich in L-Theanine, a rare amino acid that actually promotes a state of relaxation and well-being by acting upon the brains functioning. While stress can induce beta waves an excited, more agitated state, L-Theanine creates alpha waves, which lead to a state of relaxed alertness. And while L-Theanine is common in all tea, matcha may contain up to five times more of this amino acid than common black and green teas.
Green tea leaves are initially processed by soaking in an alcohol solution, which may be further concentrated to various levels; byproducts of the process are also packaged and used. Extracts may be sold in liquid, powder, capsule, or tablet form. Decaffeinated versions are also available. Green tea extract supplements are accessible over the counter in various forms.
One study that was published in the February 2010 issue of the Journal of Agricultural and Food Chemistry investigated the effects of catechins on eye diseases and found that consuming more catechins may help protect the eyes from oxidative damage and vision loss. Scientists involved in the study found evidence that catechins can pass from the digestive tract of rodents to the tissues of their eyes and reduce oxidative stress for up to 20 hours after ingestion. (11)
Another big draw health benefit-wise is that matcha, like green tea, is loaded with antioxidants. A study, published in 2014, found the plant also had antimicrobial properties, particularly the four types of catechins (antioxidant properties flavonoids) it contains, against a few different types of microorganisms. Yet another study, published in Nature, proved that catechins inhibit the growth of a bacteria called Fusobacterium nucleatum — the bacteria that causes cavities and periodontal disease.
Tea culture of Korea was actively suppressed by the Japanese during the Japanese forced occupation period (1910‒1945), and the subsequent Korean War (1950‒1953) made it even harder for the Korean tea tradition to survive. The restoration of the Korean way of tea began in the 1970s, around Dasolsa. Commercial production of green tea in South Korea only began in the 1970s,. By 2012 the industry was producing 20% as much tea as Taiwan and 3.5% as much as Japan. Green tea is not as popular as coffee or other types of Korean teas in modern South Korea. The annual consumption per capita of green tea in South Korea in 2016 was 0.16 kg (0.35 lb), compared to 3.9 kg (8.6 lb) coffee. Recently however, as the coffee market reached saturation point, South Korean tea production doubled during 2010‒2014, as did tea imports during 2009-2015, despite very high tariff rate (513.6% for green tea, compared to 40% for black tea, 8% for processed/roasted coffee, and 2% for raw coffee beans).