Damage to DNA can lead to uncontrolled cell growth and the development of cancerous tumors. Impairment caused by oxygen-containing molecules, including very reactive free radicals, is often marked by the presence of 8-hydroxydeoxyguanosine, or 8-OHdG. Iman Hakim of the Arizona Cancer Center and her colleagues performed a randomized, controlled study of the effects of tea drinking among heavy smokers. For four months, 118 smokers drank four cups of decaffeinated tea, either green or black, daily. The researchers determined that those smokers who drank green tea had a 31 percent decrease in their levels of urinary OhdG, suggesting that they were less susceptible to oxidative DNA damage than smokers who drank black tea or members of the control group were.
Participants in such studies are often required to drink quite a bit of tea, sometimes as much as seven to 10 cups a day. Researchers are thus investigating compounds similar to the active ingredients in green tea that could avoid this problem. Nurulain Zaveri of SRI International in Menlo Park, Calif., and her colleagues synthesized compounds similar to a component in green tea, EGCG, that has been associated with reduced risk of myriad types of cancer in humans. They manufactured two molecules that have different rings attached to a central structure similar to that of EGCG. One of these analogs, dubbed SR 13196, is better at slowing the proliferation of breast cancer cell lines than regular EGCG, whereas SR 13193 inhibits the growth factor protein VEGF in cancerous cells, the scientists found. "These analogs are not only valuable tools to clarify how green tea may fight cancer," Zaveri notes, "but are also potential chemopreventive drug candidates themselves, with perhaps better pharmacokinetic properties than have been seen with EGCG thus far."
Other results presented at the meeting suggest that the best type of cookie to eat during afternoon tea might be gingerbread. Researchers at the University of Minnesota determined that mice fed the main active component in ginger root three times a week had slower rates of cancer growth than control animals did. Ann Bode and her colleagues studied animals that had been injected with human colorectal tumor cells. Mice given -gingerol had fewer tumors than creatures that did not receive the compound. In addition, the tumors that did develop were smaller. In future studies, the scientists plan to feed the mice -gingerol only after their tumors have reached a critical size instead of administering it before tumor cells are introduced. "The new experiments should be more clinically relevant," Bode says. "They will get at the question of whether a patient could eat ginger to slow the metast [spread] of a nonoperable tumor."