On the last day of the National Breast Cancer Awareness Month or the pink month, we publish a report below to share with readers a few studies that suggest drinking green tea may not help cut risk of breast cancer.

A new Japanese study suggests that drinking green tea may not help reduce risk of breast cancer.

The study was unable to find an overall association between green tea intake and the risk of breast cancer among Japanese women.

The study was led by Dr. Motoki Iwasaki from the Research Center for Cancer Prevention and Screening of the National Cancer Center in Tokyo and reported in the Oct 28 issue of the journal Breast Cancer Research.

It should be noted that the results may be only applicable to Japanese women as overall dietary habits may have an impact on the risk of the malignancy that was not considered in the current study.

For the study, the researchers analyzed data from 53,793 Japanese women who were surveyed between 1995 and 1998 for their green-tea drinking habits.

During about 14 years of follow-up, 350 cases of breast cancer were recorded.

Compared with women drinking less than one cup of green tea per week, those who drank 5 or more cups per day were 12 percent more likely to be diagnosed with breast cancer. But the association was not statistically significant.

In addition, compared with those who drank less than one cup of Sencha or Bancha/Genmaicha per week, those drinking 10 or more cups per day did not face reduced nor increased risk of breast cancer.

The analysis did not include other confounders which may affect the results of the study.

Professor Jennifer Hu at the University of Miami School of Medicine was cited by healthday.com as saying the problem with this study is that it did not take into consideration other factors.

Iwasaki et al. also conducted another case-control study and again found no overall association between plasma tea polyphenols, which indicated intake of green tea, and the risk of breast cancer in Japan.

The results were published in the May 2010 issue of Breast Cancer Research and Treatment.

However, not all studies came to the same conclusion.

Dr. Jianfen Luo and colleagues at Vanderbilt Epidemiology Center found women who had highest levels of urinary epicatechin, a green tea component were 41 percent less likely to develop breast cancer compared with those with lowest levels of this polyphenol after data were analysed using Spline regression.

This association resulted from a comparison between 353 women with breast cancer and 701 controls who did not. Both study subjects and controls aged 40 to 70 were enrolled in the Shanghai Women's Health Study.

But the researchers did not find a linnk between levels of urinary polyphenols and breast cancer risk when multivariate conditional logistic regression analyses were used to assess associations.

It seems that results differed depending upon the statistical method used for the analysis.

Dai Q. and colleagues also at Vanderbilt School of Medicine published a study in the Jan 2010 issue of Annals of Epidemiology saying women started drinking green tea at 25 or younger were 31 percent less likely to develop premenopausal breast cancer, compared to non-drinkers. 

But these women were 39 percent more likely to be diagnosed with postmenopausal breast cancer.

The results suggest that women started drinking green tea at younger age may delay the onset of the disease.

Overall, there seems to be no solid evidence to suggest drinking green tea may reduce risk of breast cancer.  But it needs to be remembered that studies may not always be free or errors and biases.

A recent study suggests that people who claim to be a green tea drinker may actually have little intake of green tea polyphenols if they only drink bottled green tea.

The study led by Dr. Shiming Li found most bottled green tea samples from the market contained no EGCG or Epigallocatechin gallate - the active component in green tea that has been known to promote apoptosis or programmed cell death.

Dr. C. S. Yang and colleagues at Rutgers University have conducted a great deal of research on green tea polyphenols and risk of a variety of cancers.

Yang and Wang X published a review in the Oct 2010 issue of Nutrition and cancer saying extracts of green tea and green tea polyphenols inhibit the formation and development of cancers in animals, including skin, lung, oral cavity, esophagus, stomach, intestine, colon, liver, pancreas, bladder, mammary gland, and prostate cancers.

However, the authors did not mention any evidence suggesting that drinking green tea may help prevent breast cancer.

Breast cancer is diagnosed in more than 175,000 women and kills about 50,000 each year in the United States, according to the National Cancer institute. The disease is expected in one in seven women in their lifetime.

After the National Breast Cancer Awareness Month, more reports will be published here at foodconsumer.org to help readers better understand the risk of breast cancer and how to prevent it. 

By David Liu