In most areas of medicine, prevention is foremost in discussions about any disease process. October is Breast Cancer Awareness Month, and while most of the focus is on early detection and advances in treatment, we’d like to briefly review new information regarding possible prevention.
The focus on detection and treatment is understandable from the viewpoint that little is yet known about what causes breast cancer or what can be done to lower an individual’s risk for developing the disease. It has long been known that there are some things that are associated with a lowered lifetime risk, such as younger age at first childbearing, breastfeeding your infants, or absence of a family history of the disease. The problem is that these are only associations and therefore not really modifiable – women do not plan childbearing at an early age to lower their lifetime risk of breast cancer. And unlike many other disease processes, there is pathetically little that can be offered in the way of a modifiable lifestyle that has been shown to lower the risk of developing breast cancer.
It is for this reason that a recent article in the International Journal of Cancer caught our attention. A group of researchers at USC studied the association of green tea intake and the risk of breast cancer in Asian women. There were two reasons for their interest. First, Asian women are known to have a substantially lower risk than other nationalities of developing breast cancer and their diet traditionally includes the regular intake of green tea. Second, green tea has high concentrations of certain antioxidants. Research over the last several years has increasingly focused on the potential role of antioxidants in preventing the development of cancer. Cancer theory suggests that one of the undesirable byproducts of cell metabolism is the release of chemicals, called free radicals, that damage DNA. Cumulative damage disrupts cellular function and is felt to be a key step in the cells becoming cancerous. Antioxidants are compounds that inactivate these free radicals. Less cellular damage occurs and, theoretically, the risk of cancer decreases.
Many compounds function as antioxidants. The ones in green tea are called polyphenols (these compounds are present in all tea leaves but are destroyed in the processing of black tea, the ordinary tea most Americans drink). The researchers studied a group of Asian women in southern California who had developed breast cancer and compared them with other Asian women from the same area who had not developed the disease. They showed an inverse relationship between green tea consumption and the risk of breast cancer. That is, the higher the intake of green tea, the lower the risk of developing breast cancer. Interestingly, the actual amount of green tea consumed by these Asian-American women was not all that high. Only 1 in 5 women drank it 5 or more days a week, and a protective effect was seen even with lower consumption than this. According to their data, women who consumed the higher level (>5 cups per week) had a relative risk of developing breast cancer almost 50% lower than those who drank none. Women consuming <5 cups per week still demonstrated an almost 30% risk reduction. Also of note was the fact the lowered risk was seen even in women who had other risk factors that would, statistically anyway, increase their breast cancer risk such as a family history of breast cancer and increased level of alcohol intake. As one more side issue evaluated in this study, they looked at the association of soy intake to see if it also had any effect on the risk of breast cancer. Soy is a food source also traditionally consumed in greater quantities by Asians. It contains significant amounts of a different group of antioxidants. An inverse association was again seen. The protective effect was noted in women who did not consume green tea-which supports other research on the beneficial effect of soy products. What to infer from this? This does not imply a radical diet change is indicated. What it does do is begin to define a proactive change in diet that specifically addresses a woman’s breast cancer risk. For too long we have had little or nothing to offer as preventive guidance in this area. The gradual addition of green tea and soy products is a reasonable start.