When green tea is produced the leaves are not allowed to oxidize. This means that leaves will retain much of their vegetable characteristic – a taste that could be compared to grass, hay or algae.
Green tea is known for its health benefits, and there are many reports suggesting that it could help prevent disease. Since the leaves doesn’t go through any oxidation, much of the nutrients will remain in the finished product, and thus the antioxidants, vitamins and minerals will be released into your cup of tea.
Chinese and Japanese Green Tea
In China, the leaves are roasted in large pans in order to inactivate the enzymes that would otherwise start the oxidation process. This gives Chinese green tea a bright orange colour, but the leaves remain green, and the tea will often have a slightly burnt flavour.
The Japanese use a different method in order to stop the oxidation process. Hot steam is used to inactivate the enzymes, and this gives the leaves a more vegetable flavour that is often described as grassy. Japanese green tea has a green to yellow colour.
Tea has been used as a medicine for about 2,000 years in China. Nowadays it is however mainly drunk as a social beverage, and it’s also much appreciated for its delicate flavour and the refreshing and stimulating effects.
Green tea is furthermore rich in polyphenols (a kind of antioxidant). A subgroup of these are called catechins, and one of these catechins is called EGCG (Epigallocatechin Gallate). EGCG appears to be a very powerful antioxidant that can fight cancer. Research indicates that EGCG is able to kill cancer cells by preventing new blood vessels from forming. These vessels could otherwise help the cancer cells to grow.
It’s however primarily in laboratories and animal tests that green tea have shown positive results against cancer. There are also some studies on humans with good results, but there are also studies that show no positive effects.
Live Longer with Green Tea
Green tea may also prolong life expectancy, at least if you are Japanese. Forty thousand Japanese men and women participated in an epidemiological study. Researchers observed them during eleven years (1995–2005) and examined cause-specific deaths during seven years (1995–2001).
The researchers looked at whether consumption of green tea was correlated to deadly cancer, cardiovascular disease, and a number of other causes of death. They found a negative correlation between green tea consumption and premature death.
One to two cups of green tea per day reduced the risk of dying prematurely (all causes). The effect was most apparent for women, cardiovascular disease and a high tea consumption. Women who drank a high amount of green tea, five cups or more per day, reduced the risk of dying prematurely (all causes) by 23 percent, this compared to those who drank less than one cup per day. The reduced risk for men was only 12 percent.
When isolating the numbers for cardiovascular disease, women had a 31 percent risk reduction and men 22 percent. The researchers did however not find any protective effect against cancer.
Source: Kuriyama, S. et al. Green Tea Consumption and Mortality Due to Cardiovascular Disease, Cancer, and All Causes in Japan: The Ohsaki Study. JAMA. 2006;296(10):1255-1265 (doi:10.1001/jama.296.10.1255)
Green tea is also used as an ingredient in skin lotions and other skin care products, because the tea leafs can protect the skin from the sun.
In Japan it’s common to drink green tea with food, because it’s believed to help digestion. However, some studies suggest that green tea may reduce the absorption of non-heme iron. The iron absorption could be helped if the meal is rich in vitamin C. It’s primarily those who suffer from anaemia who need to be careful.
Storing and Preparing Green Tea
Green tea is more delicate than black tea. Therefore it’s important to store it in a proper way, and to use a water temperature of about 75–80 degrees Celsius when preparing green tea. Use one tablespoon tea leaves per cup and steep for 2–3 minutes.