October was National Breast Cancer Awareness month, and we saw pink ribbons everywhere, reminding us about the importance of early detection — or better yet, prevention. Previous research has been conflicted on the subject of green tea as a possible preventive agent against breast cancer. While animal studies have shown promise, larger studies in humans have found no significant relationship between green tea and breast cancer.
A recent study published in Breast Cancer Research followed nearly 54,000 Japanese women for 14 years in the hopes of determining a link between green tea consumption and breast cancer prevention. The women completed a questionnaire about their level of green tea consumption at the beginning of the study. Five years later, they were mailed a similar questionnaire, and this one focused on which specific type of green tea they drank, Sencha or Bancha/Genmaicha. During the follow up period, 350 women developed breast cancer. During the statistical analysis, the women were broken up into categories of green tea consumption ranging from 1 cup per week, to greater than 5 cups per day, and the percentages of those who were diagnosed with breast cancer in each group were compared. Ultimately, those women who drank the most green tea, regardless of type, were just as likely to develop breast cancer as those who drank the least.
Because of its number of participants and lengthy follow up period, this study has a lot of credibility. However, this study focused on Japanese women, a population with a low incidence rate of breast cancer overall. Japanese women have different risk profiles when compared to Western women, possibly due to other differences in diet and/or environmental and lifestyle factors. Therefore, it is unclear whether we can apply the results of this study to Western women as well.
As we’ve previously reported, the antioxidant content of tea is compromised when the tea is bottled rather than freshly brewed. This study did not take preparation method into account. The researchers also emphasized that the consumption data was all self-reported, leaving a lot of room for measurement errors, and that the green tea these women drank may not have had enough of the antioxidant to see a benefit.
The study did not show any negative association between green tea on breast cancer risk. Even those in the highest consumption group did not have an increased risk. Green tea is rich in flavonoids, a class of compounds which are strong antioxidants linked to cardiovascular health, ovarian cancer prevention, and improved insulin resistance. Green tea also has Vitamin K, which is needed for strong bones and is a great no-calorie beverage choice for anyone looking to maintain their weight or drop a couple pounds. There are still plenty of reasons to keep filling up that tea cup!