Coffee consumption and breast, ovary and endometrial cancers

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Coffee and breast cancer

Research to date has not linked coffee consumption to an increased risk of breast cancer overall. Data in pre-menopausal women who are regular coffee drinkers suggests there may be a protective effect.

  • One meta-analysis found that coffee drinking was inversely associated with breast cancer risk (relative risk 0.94)8.
  • The results of a French prospective study, which followed 67,703 women for 11 years, showed no relationship between coffee or caffeine intake and breast cancer risk overall79.
  • The WCRF 2010 Breast Cancer Report does not mention coffee as a risk factor80.
  • IARC’s 2016 review concluded that studies show either no association, or a modest inverse association, between breast cancer risk and coffee consumption1.

Post-menopausal women

Studies have shown no association between coffee consumption and the incidence of breast cancer in post-menopausal women.

  • The main studies include large samples from French, Italian and Swedish populations followed up for 6-10 years6-8.
  • A meta-analysis of 9 cohort and 9 case-control studies suggested that increasing coffee consumption by 2 cups daily tended to reduce the risk of breast cancer81. However, the results showed a borderline significant association between coffee consumption and reduced risk of breast cancer in the United States and Europe, but not in Asia. This difference may originate in the limited sample size of studies conducted in Asia. Furthermore, coffee consumption did not appear to be associated with an altered risk of benign breast disease and subsequent development of breast cancer.
  • In addition, a large Dutch study found no association between coffee and the risk of breast cancer across all levels of intake, and no link with either lifestyle or body mass index (BMI)82.
  • A Swedish study of 5,929 women (2,818 cases and 3,111 controls) showed a significantly lower risk of non-hormone receptive breast cancer in heavy coffee drinkers (more than 5 cups a day) compared to those who drank less than 1 cup a day83.
  • 2 further meta-analyses were published in 2013 84,85: one suggested that coffee/caffeine intake might be weakly associated with breast cancer risk for post-menopausal women (59,018 breast cancer cases, 966,263 participants)84. The second (49,497 cases) concluded that increased coffee intake is not associated with a significantly reduced risk of breast cancer, but reported an inverse association in oestrogen receptor negative cases85.

Pre-menopausal women

In pre-menopausal women, the consumption of regular coffee (4 cups a day) has been associated with a 38% lower risk of breast cancer (relative risk 0.62)6.

  • In pre-menopausal women who carry the BRCA1 and BRCA2 mutation, a 2006 study suggested that the risk of breast cancer is reduced by 25-70% with daily consumption of 4-6 cups of coffee, compared to non-coffee drinkers. However, this effect is limited to regular coffee; it is not observed with decaffeinated coffee86. In contrast, a 2013 study reported a significant association between coffee consumption and breast cancer risk for BRCA1 mutation carriers84.
  • The risk of breast cancer is also modulated by the CYP1A2 gene, and the interaction between coffee consumption and the polymorphisms A and C of this gene have been studied. Women carrying at least one C allele (AC or CC), who consume coffee, have a 64% reduced risk compared to non-coffee drinkers. Coffee has not been shown to have an effect in women with the AA genotype87.

Clearly further research is required to clarify the detail in this area, and integrating individual genetic variability when assessing diet-disease associations is likely to be important.

Coffee and ovarian cancer

Ovarian cancer is the fifth most common and lethal cancer in women in Europe4. Research to date has shown no conclusive association between coffee consumption and risk of ovarian cancer.

  • A meta-analysis of 8 well controlled case-control studies and 3 prospective cohort studies found that coffee consumption did not have an effect on the development of ovarian cancer88.
  • A 2012 meta-analysis based on data from all women taking part in the European Prospective Investigation into Cancer and Nutrition (EPIC) also concluded that the studies reviewed by the authors do not provide sufficient research to support an association between coffee and tea consumption and risk of ovarian cancer89.
  • The WCRF 2014 Ovarian Cancer Report lists coffee under ‘Limited Evidence – No Conclusion’90.
  • IARC’s 2016 review concluded that there is inadequate evidence to suggest an association between coffee consumption and ovarian cancer1.

Coffee and endometrial cancer

The majority of data available suggests that coffee consumption is linked to a lower risk of endometrial cancer. IARC’s 2016 review found that many epidemiological studies showed reduced risks for cancers of the uterine endometrium1.

  • A meta-analysis, including 2 cohort (201 cases) and 7 case-control studies (2,409 cases), showed that coffee drinkers were 20% less likely to develop endometrial cancer than non-coffee drinkers (relative risk 0.80), but there was significant heterogeneity between the studies91. Compared with non-drinkers, low-to-moderate coffee drinkers (1-4 cups per day) had a 13% lower risk (relative risk 0.87) of endometrial cancer and heavy drinkers (more than 4 cups per day) had a 36% lower risk (relative risk 0.64). The risk was reduced by 7% for each additional cup of coffee per day. The data suggests an inverse relationship between coffee and endometrial cancer but the causality is unclear.
  • 3 later studies not included in the above meta-analysis also concluded a dose-dependent effect of coffee consumption on reduced risk of endometrial cancer. In American women, those who drank more than 2 cups of coffee a day had a 29-35% lower risk of developing endometrial cancer than non-coffee drinkers92,93. Overweight Swedish women who drank coffee also had a lower risk of endometrial cancer94.
  • A further meta-analysis found a 26% reduction in the risk of endometrial cancer among coffee drinkers, compared with non-drinkers, and a reduction in risk of over 30% among heavy coffee drinkers8.
  • A 2012 meta-analysis including 6,628 endometrial cancer cases suggests that increased coffee intake is associated with a reduced risk of endometrial cancer, consistently observed for cohort and case-control studies95.
  • One of the meta-analyses published in 2015 supported earlier findings that coffee and caffeine intake might significantly reduce the incidence of endometrial cancer. The inverse association between coffee intake and endometrial cancer incidence was more pronounced in patients who were never treated with hormones and subjects with a body mass index >25kg/m2 96. A second meta-analysis suggested a weak association for coffee consumption, but the authors acknowledged that there may have been selective publication of only part of the research in some of the prospective studies97.
  • The WCRF 2013 Endometrial Cancer Report lists coffee under a probable decrease in risk, and mentions that the effect is found in both caffeinated and decaffeinated coffee and cannot be attributed to caffeine98.
  • IARC’s 2016 review concluded that the scientific research showed an inverse association between coffee consumption and risk of developing endometrial cancer1.

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