Breast, ovary and endometrial cancers

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 actually be a protective effect^5,74-76. The International Agency for Cancer Research (IARC) 2016 review concluded that studies show either no association, or a modest inverse association, between breast cancer risk and coffee consumption¹.

The World Cancer Research Fund (WCRF) 2018 Breast Cancer Report does not mention coffee as a risk factor⁷⁷. Variable results have been observed, associated with different genetic mutations. 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.

• A 2011 meta-analysis found that coffee drinking was inversely associated with breast cancer risk (relative risk 0.94)⁵

• A 2011 a French prospective study, which followed 67,703 women for 11 years, showed no relationship between coffee or caffeine intake and breast cancer risk overall⁷⁴

• A 2021 meta-analysis and dose response found a negative correlation between coffee intake and breast cancer risk, especially in post-menopausal and European women⁷⁵

• A 2021 narrative view of coffee consumption and breast cancer risk in the general population concluded that there is no evidence of an association between coffee intake and breast cancer risk, and there may be a slight protective effect. In postmenopausal women, and in those carrying the BRCA1 mutation, coffee is inversely associated with breast cancer risk. The effects of coffee in other sub groups is less clear and needs further investigation⁷⁶.

Post-menopausal women

Studies have shown no association between coffee consumption and the incidence of breast cancer in post-menopausal women^76-78.

• A 2011 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 day⁷⁸

• Two, 2013 meta-analyses were published^79,80. 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), although the association for BRCA1 mutation carriers was noted as needing further investigation⁷⁹. 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 a specific subgroup (oestrogen-receptor negative). The authors suggested further work was required to clarify associations⁸⁰

Pre-menopausal women

In pre-menopausal women, the consumption of regular coffee (4-6 cups a day) has been associated with a lower risk of breast cancer⁸¹.

• In pre-menopausal women who carry the BRCA1 and BRCA2 mutation, a 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 coffee⁸¹.

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 genotype⁸².

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^83-85. The WCRF 2018 Ovarian Cancer Report lists coffee under ‘limited evidence - no conclusion’⁸⁶, and IARC’s 2016 review also concluded that there is inadequate evidence to suggest an association between coffee consumption and ovarian cancer¹.

• 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 cancer⁸³

• A 2019 dose response meta-analysis found no association between the risk of ovarian cancer and coffee consumption (caffeinated or decaffeinated) and caffeine intake⁸⁴

• A 2019 further systematic review and meta-analysis concluded that there was no association between total caffeine intake and ovarian cancer risk. However, the authors did find an inverse association between decaffeinated coffee consumption and the risk of ovarian cancer⁸⁵.

Coffee and endometrial cancer

The majority of data available suggests that coffee consumption is linked to a lower risk of endometrial cancer^5,87-90. IARC’s 2016 review found that many epidemiological studies showed reduced risks for cancers of the uterine endometrium¹. The WCRF 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 caffeine⁹¹.

• A 2011 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 drinkers⁵

• 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 studies⁸⁷

• Two 2015 meta-analyses were published^88,89. One 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/m^{2 88}. The second 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 studies⁸⁹

• A 2018 meta-analysis of 12 cohort studies and eight case-control studies with 11,663 participants and 2,746 endometrial cancer cases concluded that the results strengthened the evidence of a protective effect of coffee consumption on the risk of endometrial cancer, and in particular that increased coffee intake might be beneficial for women with obesity⁹⁰