All true teas---green, black and white---contain disease-fighting antioxidants because they come from the same plant. But green tea has much higher levels than most of catechin, a particularly potent antioxidant. While the evidence to support green tea's use in preventing or treating any health problem is not crystal clear, research in both animals and humans has shown some possible associations between these naturally occurring antioxidants in green tea and protection against health problems that affect men. Many of the studies showing positive results have been performed in Asian countries, where large populations of men drink green tea on a regular basis.
One animal study, supported by the World Health Organization and published in 2004 in The Journal of Nutrition, showed that antioxidants in both green and black teas can lower both systolic and diastolic blood pressure measurements. A human study, conducted by researchers from Harvard Medical School, Brigham and Women's Hospital and the University of Florida, confirmed that green tea can reduce blood pressure slightly and also reduces total cholesterol and levels of a marker of chronic inflammation, which is also linked to cardiovascular disease. A review of epidemiological studies in Japan, also published in The Journal of Nutrition in 2008, indicated that more than half of the randomized studies performed in parts of that country outlined a positive benefit of green tea or green tea supplements on cardiovascular disease and strokes.
The antioxidants in green tea may protect against some, but not all, cancers. Studies performed in China indicated that regular tea drinks have half the risk of developing stomach and esophageal cancers than those who don't drink as much tea. Yet another Chinese study found that the longer and more often men drank green tea, the lower the risk of prostate cancer. Yet ongoing studies at the National Cancer Institute (NCI) in the U.S. have found very little anti-tumor effect among prostate cancer patients. The NCI is also looking at green tea's ability to protect against skin cancer, in supplement form and as a topical application.
A Japanese survey of 940 men, published in 2009 in the Journal of Periodontology found that men who regularly drank green tea had fewer instances of gum disease. Researchers believe the association may be due to the power of green tea's antioxidants to reduce inflammation.
Green tea has also been found to have antibacterial and antibiotic properties that may boost the capabilities of medications that are currently in use and enable them to fight some of the newer strains of bacteria that are resistant to conventional antibiotic treatments.