Study: green tea consumption and breast cancer risk

Reference

iwasaki m, inoue m, sasazuki s, et al. Drinking green tea and the resulting breast cancer risk in a population -related cohort of Japanese women. breast cancer res. 2010; 12 (5): R88.

Design

This is a prospective study that accompanied 53,793 women in Japan. In this group of women, 581 cases of breast cancer were newly diagnosed within the first 5 years. After the first 5-year follow-up examination from 1995 to 1998, 350 further cases were newly diagnosed in 43,639 women during the 9.5-year follow-up examination. With the help of questionnaires that were carried out at the beginning of the course, the frequency of the entire consumption of green tea was determined. In the case of follow-up examinations after 5 years, the frequency of the consumption of sencha and bancha/genmaicha green tea was assessed and associated with breast cancer incidence over a period of 13.6 years.

most important knowledge

This prospective study showed no statistically significant difference in the frequency of breast cancer in women who consumed more than 5 to 10 cups of green tea (1 cup of tea = 4 ounces tea) per day, compared to women, which over a period of less than one cup per day consumed average afternoon period of 13.6 years. Compared to women who drank less than 1 cup of green tea a week, the adapted hazard ratio (HR) was 1.12 (95 %confidence interval) for women who drank 5 or more cups a day). [CI] 0.81–1.56; P for trend = 0.60) in the basic data. Compared to women who drank less than 1 cup of Sencha or Bancha/Genmaicha per week, the adapted HRS for women who drank 10 or more cups per day were 1.02 (95 %KI 0.55–1.89; p for trend = 0.48). and 0.86 (0.34–2.17; p for trend = 0.66) for Bancha/Genmaicha. Neither the hormone receptor status of breast cancer nor the menopause status influenced these results.

effects on practice

This large -scale, population -based prospective cohort study in Japan, together with two other Japanese cohort studies, ^{1,2 refuted the results of several prospective studies, which had previously shown a statistically significant reduction in breast cancer risk in women, the large amounts of green tea Consumed. 3.4.5 The results of this study also contradict smaller prospective studies, which prove statistically significant increases in the disease-free survival in strong green tea consumers, which were previously treated for breast cancer in the early stage. In addition, a prospective study from China showed a statistically significant reduction in pre -menopausal breast cancer risk in women who consumed large amounts of green tea from the age of 20.}

Even if the results of this study contradict some previous studies, there are several reasons to seriously consider this latest study. The study was prospectively designed, a strong study design. The study had the advantage that there were big differences in regular consumption of green tea - from less than 1 cup of up to more than 10 cups a day. About 12 % of women drank less than 1 cup of green tea per week in the basic data and 27 % drank 5 or more cups a day. In the 5-year follow-up data, 22 % or 30 % of women did not drank a Sencha and Bancha/Genmaicha, while 5.2 % or 2.5 % 10 or more cups per day drank. The response rate of over 80 % on the questionnaire underpinned the statistical analysis. While the self -disclosure via a questionnaire may have led to inaccurate results, the validity of the questionnaire was confirmed by a validation study. ^{6 In addition, these researchers previously used the same study design and the methodology and made a connection between the consumption of green tea and a lower risk for distal gastric cancer and advanced Prostate cancer. This would indicate reliable methodology. No drinking methods were controlled in the study that could possibly have had an impact on the overall availability of polyphenol. However, the researchers led a nested case control study through 7 as part of this study and did not find any overall context between plasmatee polyphenols and the risk of breast cancer, which reduces the likelihood that the preparation method of the green tea influences the results. Essentially, this study provides a fairly strong argument that the consumption of green tea for Japanese women living in Japan has no benefit for breast cancer prevention.}

It is important to recognize that other cohort studies have shown a statistically significant benefit in other population groups - especially in Chinese women who have started consuming green tea before the age of 25 and in which the risk of breast cancer is lower before menopause. In addition, Japanese women who live in the United States and who have already been diagnosed with breast cancer in the early stages and who have received final treatment, benefit from the consumption of at least 8 cups of green tea per day and thus increase their chance to survive. In a group of women who already have a relatively low risk of developing breast cancer, the frequent consumption of green tea is not an effective prevention strategy. The lack of benefits in this study could also be due to the fact that the entire polyphenol consumption of food in Japanese standard diet is quite high. This can cover up the effect of the polyphenols from green tea, even if it is consumed in relatively large quantities.