The medicinal powers attributed to green tea come from catechins, potent antioxidants that boast an array of health-promoting properties. For starters, they can destroy certain bacteria and viruses, enhance the immune system, and combat several forms of cancer, including prostate cancer. Although there are several different kinds of catechins, the most powerful is epigallocatechin gallate, EGCG.
The amount of catechin in green tea varies depending on where the tea is cultivated, the diversity of plants used, the harvest season, and how it is processed. Generally, Japanese green tea has a greater EGCG content than does Chinese tea, but within these two categories there are differences as well. According to an analysis of EGCG content in different types of green tea conducted by the authors of Foods to Fight Cancer, Sencha uchiyama (a Japanese green tea) is superior to a dozen other Japanese and Chinese green tea varieties. (Beliveau 2007)
Other Japanese green teas that rank high in EGCG content include Gyokuro, Sencha, and Matcha. The most nutrient rich green tea is Matcha, which contains 10 times the amount of EGCG than other green teas. When choosing Matcha green tea, select one from Japan that has been steamed, not roasted or pan-fried, and that has been stone ground into a fine powder. These processing details are what make Matcha green tea nutritionally superior to other green teas. Although Matcha green tea takes a little longer to prepare, the extra time (and higher cost) are well worth the health benefits. Chinese green tea that is roughly equivalent to Matcha is pito chun emperor; other Chinese green teas that have a lesser amount of EGCG than Matcha and Pilo chun emperor are YHunnan, Yuzan, Paimutan, Meng ding, Lung chin, Dong ding, Pou chong, and Tikuan yin. Regardless of which green tea you buy, choose organic.
The four main types of tea are white, green, oolong, and black, yet they all come from the same plant, Camellia sinensis. Processing is what determines the “color” and the qualities of each types of tea.
White tea is the least processed. The leaves are picked before they even open up, and at that point they are covered with fuzzy white hairs, which gives the tea its name. The leaves are simply steamed and dried. Studies indicate that white tea offers more antioxidant properties than the other teas, but it is much more difficult to find in stores.
Oolong tea (or wu long) is a combination of green and black leaves, which are partly fermented, which makes it stronger than green tea but more delicate than black teas, which are fully fermented. Black tea, the type most commonly consumed around the world, undergoes the most processing before it makes its way into teabags. To make black tea, the leaves are oxidized, which means they are exposed to the air for a specific amount of time to allow natural chemical reactions to occur. These reactions change the leaves’ color from green to copper and intensify their flavor until it is rich.
Green teas are not oxidized; instead the leaves are allowed to wither and dry without processing. The lack of oxidation allows the leaves to retain the essential substances that give green tea its potent properties.
The ability of green tea to impact prostate cancer is impressive. Studies of large populations of men have shown that those who consume green tea regularly are less likely to develop prostate cancer than men who do not drink the beverage. (Heilbrun 1986; Jain 1998) In other studies, researchers found that the risk of prostate cancer decreases proportionally as the amount, frequency, and duration of green tea consumption increases. (Jian 2004)
In terms of amount of tea consumed, men who drank more than three cups of green tea daily showed a reduced risk of prostate cancer. In a large study that evaluated the green tea drinking habits of 49,920 men aged 40 to 69 who were followed for at least 10 years, the investigators found that men who consumed five or more cups of green tea daily had a reduced risk of advanced prostate cancer when compared with men who drank less than one cup daily. (Kurahashi 2008)
- It interferes with the activity of an enzyme called ortnithine decarboxylase, which plays a role in the “birth” of prostate cancer (Gupta 1999)
- It slows the growth of human prostate cancer cells and prompts them to “commit suicide” (apoptosis) (Gupta, Ahmad 2000)
- It encourages the repair of damaged DNA that might otherwise promote cancer growth (Butt 2009)
- It inhibits the activity of an enzyme called COX-2, which accumulates in prostate cancer tissue and is involved in the prostate cancer process. (Hussein, Gupta 2005). Research shows that prescription medications called COX-2 inhibitors, such as celecoxib (Celebrex) have the ability to slow the growth of prostate cancer in animal models. However, a recent study published in Clinical Cancer Research shows that the EGCG found in green tea was nearly as effective as COX-2 inhibitors in slowing the growth of prostate cancer. (Adhami 2007)
- It stimulates the activity of certain immune system cells that fight cancer tumors. (Butt 2009)
- In a study published in the journal Cancer Prevention Research in June 2009, researchers reported that green tea polyphenols, primarily EGCG, significantly reduced the levels of PSA. The study included 26 men who had prostate cancer and who were scheduled for radical prostatectomy. (McLarty 2009)
- It also appears that catechins may benefit men who have pre-cancerous prostate lesions (prostate intraepithelial neoplasia, or PIN), a condition that indicates a high risk of developing prostate cancer. Studies indicate that 30 percent of men who have a high-grade PIN go on to develop prostate cancer within one year after repeated biopsy. In a 2006 study published in Cancer Research, 60 men who had high-grade PIN participated in the double-blind, placebo-controlled study. (Bettuzzi 2006) Men in the treatment group received three 200-mg capsules of catechins daily. After one year, only one tumor was diagnosed among the 30 treated men, compared with nine cancers found among the 30 controls. As a “bonus,” the researchers also noticed that the men who took the catechins had reduced lower urinary tract symptoms, which suggests catechins may be helpful in treating symptoms of BPH.
In a 2009 study, investigators found that decaffeinated green tea fed to mice reduced their cholesterol and triglyceride concentrations significantly, which could benefit the heart. (Richard 2009)
A 2008 article published in the International Journal of Epidemiology noted that drinking several cups of green tea every two to three days was associated with a 50 percent reduction in total stroke, cerebral infarction, and cerebral hemorrhage. (Tanabe 2008)
Some studies indicate that drinking green tea can help with weight loss.
A study conducted at the Vanderbilt School of Medicine found that women who regularly drank green tea had a slightly decreased risk for breast cancer than women who did not drink the tea. (Shrubsole 2009)
White tea is the least processed of the tea varieties. The leaves are picked before they even open up, and at that point they are covered with fuzzy white hairs, which gives the tea its name. The leaves are simply steamed and dried. The result is a tea that is barely processed, which allows it to hold onto high concentrations of its catechins.
Many claims have been made about the health virtues of white tea. One reason for the scarcity of scientific information however is that more studies have been conducted using the more readily available green and black teas. White tea is also more costly than its cousins.
Advocates of white tea say it can lower blood pressure, reduce cholesterol levels, help with weight loss, fight viruses and bacteria, support healthy gums, build strong bones and fight cancer. Studies to support these claims, including those for cancer include:
- At the 219th national meeting of the American Chemical Society about a decade ago, researchers from Oregon State University conducted an analysis and reported that white tea had more catechins than other teas. (Santana-Rios 2001) Armed with that information, they decided to test the cancer-fighting abilities of white tea using the Salmonella test, which identifies whether a substance can cause or prevent mutations in DNA, which is an early step in cancer. They discovered that white tea inhibited mutations more effectively than did green tea. The scientists attributed this superior result to the higher proportion of catechins in white tea than in green tea.
- In another study, researchers at Ohio University Southern looked at the impact of white tea, green tea, and caffeine in a colon cancer model and found that white tea helped inhibit proliferation of early lesions in the colon. (Carter 2007)