The Role of Tea
Tea is one of the most widely consumed beverages in the world. In fact, it is second only to water. Many health benefits have been attributed to tea, including possibly protecting against cancer. Three basic types of tea—black, green, and oolong—come from the Asian tea shrub. They vary by how they are processed, more specifically by the degree of fermentation involved. Green is not fermented at all, oolong slightly fermented, and black the most fermented. The health benefits are thought to come from compounds in the tea, called polyphenols, that are thought to have strong antioxidant potential. They have been shown, in animal studies, to fight cancer, bacteria, and viruses and to boost the immune system. Green tea is considered the healthiest type because it contains the most polyphenols. Black tea has been studied less but also appears to have similar beneficial effects. The typical herb teas that Americans drink do not contain polyphenols; therefore do not have the same cancer-fighting properties as the Asian teas.
Epidemiological studies suggest that green tea may be associated with a reduced risk of prostate cancer. Men in Asian countries, where it is consumed in large amounts, have low rates of prostate cancer. However, this could be due to other factors, such as more soy in the diet and less fat. But animal and laboratory studies clearly support the protective effects of green tea against all stages of cancer, from initiation to progression. It has been shown to result in the death or slowing of growth of various types of cancer cells. The actual mechanisms are not clear but may include regulation of male hormones to reduce DHT in cells, which appears to stimulate cancer development.
The big problem with tea as a preventive agent is the lack of evidence in humans. No prospective human studies have been performed, so the beneficial effects can only be speculated at this time. A big question is how much tea is needed to be protective in humans. The amount used in animal studies would be the equivalent of up to 10 cups a day in humans, much more than one would expect to consume. There is a need for human research, in view of the potential benefits, low harm (at least at normal intakes), and low costs involved with the use of tea. Some prostate protective tea products have been introduced in the U.S., usually including green tea with several other supposedly protective ingredients (e.g., saw palmetto, pygeum, Korean ginseng, soy extract, pumpkin seeds). But what is lacking is information about how much of each ingredient is present. The amounts may be so small that no beneficial effect could occur. Research needs to identify optimal amounts.
The bottom line is that green, black, and oolong teas do appear to be good for you for several reasons, possibly including prostate health. But how good and how much is needed are not known. Still, it is probably worth adding some green tea to your diet as part of an overall prevention plan.
