Is there a connection between tea and cancer prevention? There are quite a few studies that suggest that this may be the case. A number of these findings were summarized in Tea and Cancer Prevention, a document released by the National Cancer Institute, a division of the U.S. National Institutes of Health.
Though the report suggested that studies on humans have not yet provided a conclusive result, the findings indicated that it was the antioxidants in tea that help contribute to inhibiting cancer. Antioxidants are substances that allow the human body to scavenge and seize oxidants, which are unstable molecules – also known as free radicals – that damage cell proteins and genetic material.
One of the most important antioxidants and the one most likely to guard against cancer – by selectively inhibiting specific enzyme activities that lead to cancer – are the catechins. Because it is more lightly processed, green tea is thought to contain more antioxidants than the more heavily processed black tea. Regardless of the catechin content of various varieties, studies have shown that steeping for about five minutes (which is probably a bit…steep for optimum flavor) allows the tea to release more than 80 percent of its catechins.
Studies indicate that catechins in tea inhibit cancer growth in a number of ways: by scavenging oxidants before cell injuries occur, by reducing the incidence and size of chemically induced tumors, and by inhibiting the growth of tumor cells. Studies of liver, skin, and stomach cancer showed that chemically induced tumors in mice decreased in size when they were give green and black tea.
Studies on humans that showed promising findings include one in China that looked at 18,000 male tea drinkers. Researchers there found that tea drinkers were about half as likely to develop stomach or esophageal cancer as men who drank little tea. Another Chinese study discovered that drinking about two cups of tea daily, as well as applying a tea extract, reduced the size and proliferation of leukoplakia, a precancerous oral plaque.