In July 2018, I reported on a meta-analysis of coffee intake and breast cancer risk. The design of that meta-analysis was to assess associations between amounts of decaffeinated and caffeinated coffee (from 0 to 7 cups of coffee per day) and breast cancer risks, including categories of body mass index, hormone receptor status and menopause status.
The analysis included 13 prospective studies totaling over 1 million participants and concluded in showing no significant association between coffee consumption and breast cancer risk. However, when the analysis was specific to postmenopausal women, there was an inverse relationship to the tune of consumption of 4 cups of coffee per day was associated with a 10% reduction in postmenopausal cancer risk, no matter body mass index or hormone receptor status, or caffeinated or decaffeinated coffee…. Conclusion: coffee consumption is associated with a decreased risk of postmenopausal breast cancer. (Ref:  Lafranconi A, Micek A, De Paoli P, et al. Coffee intake decreases risk of postmenopausal breast cancer: a dose-response meta-analysis on prospective cohort studies. Nutrients. 2018;10(2). pii:E112.)
The current study I want to report on is the role of postdiagnostic coffee and black tea consumption among women with breast cancer in prospective cohort studies. The women who were included in this analysis were 8,900 women diagnosed with stage I through stage III invasive breast cancer from 1980 through 2010 who were part of the Nurses’ Health Study (NHS) and then also from 1991 through 2011 who were part of the NHS II.
A food frequency questionnaire (FFQ) of coffee and black tea consumption every 4 years after the diagnosis of their breast cancer was assessed. Total coffee consumption included regular and decaffeinated coffee and total tea consumption included regular and decaffeinated tea.
Approximately 70% of the women in the study had data including estrogen and progesterone receptor status, human epidermal growth factor receptor 2, cytokeratin 5/6, Ki-67 and epidermal growth factor receptor. These are common markers analyzed from breast tumor biopsies. Researchers gathered data every 2 years postdiagnosis.
The investigators reported on 1,054 deaths due to breast cancer and 2,500 total deaths over 30 years of follow-up. A higher postdiagnostic coffee consumption was associated with a lower mortality specific to breast cancer. Women who drank > 3 cups of coffee per day had a 25% lower risk when compared with non-coffee drinkers. There was also a lower mortality rate due to any cause observed in the coffee drinkers. Compared with women who did not drink coffee, > 2 to 3 cups per day was associated with a 24% lower risk and > 3 cups/day was associated with a 26% lower risk. Post diagnostic tea consumption was also associated with lower all-cause mortality. Greater than 3 cups/day was associated with a 26% lower risk compared to nondrinkers but not a reduction in breast cancer specific mortality.
In addition, the more you drank the better the effect. For each 1 cup/day greater intake, the breast cancer mortality hazard ratio dropped 7% for regular coffee and 2% for decaffeinated coffee. There was also a benefit for reduction of all-cause mortality for greater intake for both regular and decaffeinated coffee. For each 1 cup of caffeinated coffee per day, the hazard ratio dropped 7% and 5% for decaffeinated.
When the intakes of coffee and tea were added together, an inverse association with breast cancer specific mortality was seen for consumption of > 3 cups/day vs nondrinkers, but not for tea of > 3 cups/day vs nondrinkers. For all-cause mortality, significant inverse associations were seen for both coffee and tea at > 3 cups/day vs nondrinkers.
In breast cancer survivors, higher amounts of coffee consumption after breast cancer diagnosis was associated with better survival rates from breast cancer and from any cause.
Commentary: I can’t tell you how many patients tell me they are going off of coffee, or they already went off coffee. I then ask….why? More often than not, I recommend they continue their coffee (and black tea) habit. If they don’t have heart palpitations or a rapid heart rate or chronic insomnia, or perhaps breast tenderness, I do not see a reason to discontinue, and in fact proceed to tell them the benefits.
You might be surprised to learn that coffee is a robust source of antioxidants and in 2005, it was listed as the #1 source of antioxidants in the American diet, providing almost 1,300 mg of antioxidants daily in the form of polyphenols. Black tea provides 294 mg and bananas 76 mg. I list these two because they are the second and third dietary sources of polyphenols in the American diet. That’s actually not particularly fabulous to me… as I would prefer a diet richer in other polyphenol-rich foods (berries, citrus, red fruits, apples) and then preferably lower glycemic fruits than bananas (berries again). And, we haven’t even gotten to the other robust nutrients and fibers in the long list of polyphenol-rich foods.
Past studies examining the relationship between coffee consumption and breast cancer mortality are inconsistent, but the current study is the most comprehensive. It’s curious why coffee drinking spurs negative health concern…now it could be the sugar added, or the croissant or scone with the coffee. Worse, smoking a cigarette with your coffee. I would agree with those negatives. But when it comes to having breast cancer, coffee should be encouraged, not discouraged. And while not all like the taste of coffee, she can at least be encouraged to drink her black tea…as it will reduce her risk of all-cause mortality, even if not breast cancer mortality.
Reference: Farvid M, Spence N, Rosner B, et al. Post-diagnostic coffee and tea consumption and breast cancer survival. Br J Cancer. 2021; 124(11):1873-1881.