Coffee and Tea Consumption and Risk of Pre- and Postmenopausal Breast Cancer in the European Prospective Investigation Into Cancer and Nutrition (EPIC) Cohort Study

Nirmala Bhoo-Pathy; Petra HM Peeters; Cuno SPM Uiterwaal; H Bas Bueno-de-Mesquita; Awang M Bulgiba; Bodil Hammer Bech; Kim Overvad; Anne Tjønneland; Anja Olsen; Françoise Clavel-Chapelon; Guy Fagherazzi; Florence Perquier; Birgit Teucher; Rudolf Kaaks; Madlen Schütze; Heiner Boeing; Pagona Lagiou; Philippos Orfanos; Antonia Trichopoulou; Claudia Agnoli; Amalia Mattiello; Domenico Palli; Rosario Tumino; Carlotta Sacerdote; Franzel JB van Duijnhoven; Tonje Braaten; Eiliv Lund; Guri Skeie; María-Luisa Redondo; Genevieve Buckland; Maria José Sánchez Pérez; Maria-Dolores Chirlaque; Eva Ardanaz; Pilar Amiano; Elisabet Wirfält; Peter Wallström; Ingegerd Johansson; Lena Maria Nilsson; Kay-Tee Khaw; Nick Wareham; Naomi E Allen; Timothy J Key; Sabina Rinaldi; Isabelle Romieu; Valentina Gallo; Elio Riboli; Carla H van Gils

Disclosures

Breast Cancer Res. 2015;17(15) 

In This Article

Discussion

In this study, high versus low caffeinated coffee intake was associated with a modest but statistically significantly lower risk of postmenopausal breast cancer. This association was only detected in women not consuming decaffeinated coffee. Although abstinence of decaffeinated coffee (versus any intake, irrespective of caffeinated coffee intake) seemed to be associated with lower risk for postmenopausal breast cancer, exclusive decaffeinated coffee intake was not associated with increased risk. Tea intake was not associated with risk of postmenopausal breast cancer. Neither caffeinated coffee, decaffeinated coffee, nor tea intake impacted the risk of premenopausal breast cancer.

Our null finding for the association between total coffee intake and risk of postmenopausal breast cancer corroborates the findings of most previous large-scale prospective studies and meta-analyses.[12,28] The lack of association observed in the current study and previous studies seems to support the notion that studying total coffee intake as a single entity may result in a net null association owing to differences in the direction of association between caffeinated and decaffeinated coffee, in relation to breast cancer. Hence, we would like to recommend that future studies in populations consuming both types of coffee should explicitly analyze caffeinated and decaffeinated coffee intake separately.

The observation that caffeinated coffee was significantly associated with lower risk of postmenopausal breast cancer seems to be in agreement with the finding of a recent population based case–control study by Lowcock et al. in Canada (odds ratio comparing highest versus no consumption: 0.63 (95% CI: 0.43 to 0.94).[19] This study, and another population-based case–control study, which included participants from Sweden as well as Germany,[29] had further found that caffeinated coffee intake was significantly associated with a reduced risk of estrogen receptor negative breast cancers but not estrogen receptor positive breast cancers, while we found a stronger association in ER- PR- breast cancers. A cohort study in Sweden had also found that increased coffee intake was associated with lower risk of ER- PR- breast cancer, but at a more modest margin of protection, not achieving statistical significance.[30] Other recent prospective cohort studies, however, could not show an association between caffeinated coffee intake and risk of breast cancer.[31–35] While it seems plausible that caffeine plays a role in explaining the lower risk of breast cancer associated with caffeinated coffee intake in the current study,[35] a number of studies have shown that caffeine intake per se does not impact breast cancer risk.[19,32–34,36] It is hence postulated that another compound, or compounds, in caffeinated coffee may confer a protection against breast carcinogenesis by acting synergistically with caffeine.[19] This explanation seems plausible given that in our study, caffeinated coffee, which contains caffeine and a plethora of other compounds, was associated with lower risk of postmenopausal breast cancer, whereas decaffeinated coffee does not seem to be associated with risk of breast cancer.

In this study, those who reported not to consume decaffeinated coffee seemed to have a significantly lower risk of breast cancer. However, we did not observe a dose–response relationship. Cross-classified coffee intake analysis further showed that exclusive decaffeinated coffee consumption was not associated with risk of postmenopausal breast cancer compared to decaffeinated coffee and low caffeinated coffee consumption. Post-hoc analyses also showed that exclusive decaffeinated coffee consumption was not associated with increased risk of postmenopausal breast cancer compared to no intake of any coffee. Taken together, these findings seem to suggest that decaffeinated coffee intake is not associated with postmenopausal breast cancer. The apparent decrease in risk among non-consumers of decaffeinated coffee may be explained by findings of previous studies, which have suggested that decaffeinated coffee consumers may be unique in terms of lifestyle or medical history.[37,38] Decaffeinated coffee intake is related to illness in some persons but to a healthy lifestyle in others.[37] This is corroborated in the current study, where consumption of decaffeinated coffee was associated with a healthier lifestyle compared to non-consumption. Hence, there may have been minimal overlap in (lifestyle related) confounders between the consumers and non-consumers of decaffeinated coffee to allow optimal adjustment. It is also conceivable that the breast cancer screening behavior of decaffeinated coffee consumers may have contributed to higher detection of (early) breast cancers in this subgroup. This may also explain why higher caffeinated coffee intakes within decaffeinated coffee consumers were not associated with a lower risk of breast cancer. It is, however, acknowledged that distinguishing genuine decaffeinated coffee effects from a 'decaffeinated coffee preference' effect may be difficult.

A meta-analysis on the association of tea intake with breast cancer risk had found no overall protective effect of black tea (pooled relative risk = 0.97; 95% CI = 0.91 to 1.05).[3] This corroborates our findings since black tea is the predominantly consumed type of tea in Europe.[39] Possibly explaining the lack of association between black tea and breast cancer is that it contains a relatively lower amount of caffeine compared to coffee, and up to 10-fold reduction in catechin levels compared with green tea, which had been inversely associated with breast cancer.[39]

Besides having a sufficiently large number of premenopausal breast cancers, we also had a relatively high number of breast cancer cases whose hormone receptor statuses were available (approximately 70%) to allow analysis by ER and PR status. Our findings further support the view that pooling of pre- and postmenopausal breast cancers as a homogenous entity is not recommended. We do, however, acknowledge that data on menopausal status at diagnosis was not available, and we had to use age at breast cancer diagnosis as a proxy. Although coffee and tea intakes were measured only at baseline, analyses of participants in the EPIC sub-cohort of Umea in Sweden,[40] as well as participants of the Cancer Prevention Study II in the United States,[41] with repeated measures taken up to 10 years apart showed that coffee habits are stable over a long period. While the amount of coffee intake seems to vary substantially across Europe, true variation in coffee intake may not be as large as it seems given that there is an inverse relationship between the volume and concentration of coffee. This is reflected in our results whereby the hazard ratios using cohort-wide cutpoints are similar to country-specific cutpoints. We did not have information on the type of tea, and coffee/tea brewing methods, which may vary across the countries and alter the contents of potentially beneficial compounds in the beverages. It has been recently highlighted that coffee brewing methods maybe be relevant with respect to breast cancer risk. A cohort study in Sweden showed that a decreased risk of breast cancer was observed in women drinking boiled coffee but no association was observed with filtered coffee consumption.[42] Country specific categories of consumption were therefore used to address this limitation. Besides coffee and tea as prominent sources of caffeine in this population, hot chocolate, chocolate candy/candy bars, and soft drinks are also possible sources.[43] We had information on chocolate candy/candy bars intake and soft drinks, but not on hot chocolate intake. As contributions of caffeine from these sources are far lower than from coffee and tea, those intakes are unlikely to have impacted our study results.[43]

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