Farvid MS, Spence ND, Rosner BA, Willett WC, Eliassen AH, Holmes MD. Post-diagnostic coffee and tea consumption and breast cancer survival. Br J Cancer. 2021;124(11):1873-1881.
Investigators examined the role of postdiagnostic coffee and tea consumption among women with breast cancer in prospective cohort studies.
Participants included 8,900 women diagnosed with stage I through III invasive breast cancer from 1980 through 2010 who were part of the Nurses’ Health Study (NHS) and from 1991 through 2011 who were part of the Nurses’ Health Study II (NHS II).
(The NHS is an ongoing cohort study initiated in 1976 with an enrollment of 121,700 US female registered nurses aged 30 to 55 years. The NHS II was started in 1989 with an enrollment of 116,429 US female registered nurses aged 25 to 42 years.)
Investigators assessed postdiagnostic coffee and tea consumption by a validated food frequency questionnaire (FFQ) every 4 years after diagnosis. Total coffee consumption was calculated as the sum of regular and decaffeinated coffee, and total tea consumption was calculated as the sum of regular and decaffeinated tea.
Breast cancer–specific and all-cause mortality
Investigators identified breast cancers through self-reported diagnosis on the biennial questionnaires.
Breast tumor tissue was tested from approximately 70% of the women for estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (HER2), cytokeratin 5/6, Ki-67, and epidermal growth factor receptor. If tissue samples were not available, investigators obtained hormone receptor and HER2 status from medical records.
Investigators confirmed reported deaths in the National Death Index, and a study physician reviewed the death certificate and medical record to determine the cause of death.
Investigators gathered data on covariates every 2 years postdiagnosis, and data included a broad range of possible confounders.
Investigators documented 1,054 breast cancer–specific deaths and 2,501 total deaths during 30 years of follow-up. Higher postdiagnostic coffee consumption was associated with a lower breast cancer–specific mortality: Compared with nondrinkers, >3 cups/day of coffee was associated with a 25% lower risk (hazard ratio [HR]: 0.75; 95% confidence interval [CI]: 0.59–0.96; P=0.002).
Lower all-cause mortality was also observed in coffee consumers: Compared with nondrinkers, >2 to 3 cups/day was associated with a 24% lower risk (HR: 0.76; 95% CI: 0.66–0.87), and >3 cups/day was associated with a 26% lower risk (HR: 0.74; 95% CI: 0.63–0.87; P<0.0001).
Postdiagnostic tea consumption was associated with lower all-cause mortality: Compared with nondrinkers, >3 cups/day was associated with a 26% lower risk (HR: 0.74; 95% CI: 0.58–0.95; P=0.04).
For each 1 cup/day greater intake, the HR for breast cancer mortality dropped 7% for regular coffee (95% CI: 0.87–0.99) and 2% for decaffeinated coffee (95% CI: 0.91–1.06). Lower all-cause mortality was seen with greater intake of both regular and decaffeinated coffee: For each 1 cup/day greater intake, the HR also dropped 7% for regular coffee (95% CI: 0.89–0.97) and 5% for decaffeinated (95% CI: 0.91–1.00), though there were fewer consumers of decaffeinated coffee.
High consumption of tea after diagnosis was associated with lower all-cause mortality: Compared with nondrinkers, consuming >3 cups/day was associated with a 26% lower risk (HR: 0.74; 95% CI: 0.58–0.95; P=0.04). However, high consumption of tea after diagnosis was not associated with breast cancer–specific mortality.
When coffee and tea intakes were included together in the model, an inverse association with breast cancer–specific mortality was seen for consumption of coffee (>3 cups/day versus nondrinker, HR: 0.73; 95% CI: 0.57–0.94; P= 0.001) but not for tea (>3 cups/day versus nondrinker, HR: 0.76; 95% CI: 0.53–1.09; P=0.08). For all-cause mortality, significant inverse associations were observed for both coffee and tea, mutually adjusted (>3 cups/day versus nondrinker, HR: 0.71; 95% CI: 0.60–0.84; P<0.0001 for coffee; HR: 0.70; 95% CI: 0.55–0.90; P=0.005 for tea).
Among breast cancer survivors, higher postdiagnostic coffee consumption was associated with better breast cancer and overall survival.
In the summer of 2005, we were surprised by a report that coffee was the number 1 source of antioxidants in the American diet. Coffee provides the average American with almost 1,300 mg daily of antioxidants in the form of polyphenols. Black tea and bananas, the second and third dietary sources of polyphenols, provide only 294 mg and 76 mg respectively.1 This report may have been a turning point in attitudes toward coffee; rather than being harmful, coffee is believed to be good for you. We have seen a steady stream of studies linking coffee consumption to better health outcomes.
Past epidemiological studies examining the relation between coffee consumption and breast cancer mortality have been limited and the results inconsistent.
In 2012, Holly Harris reported that after examining coffee and black tea consumption in the Swedish Mammography Cohort, they found that of the 973 total deaths (of which 394 were from breast cancer) between 1987 to 2010, those women drinking 4-plus cups of coffee per day were not at significantly greater risk of dying from breast cancer or other causes than those drinking less than a cup per day. Nor did they find that drinking black tea was significantly associated with breast cancer survival.2
A 24% reduced risk of dying from breast cancer by drinking 2 to 3 cups of coffee a day is in the same ballpark as the benefit gained from undergoing chemotherapy; for most women, doing so would be less onerous.
Steven Lehrer reported in 2013 that in a group of 96 women treated for breast cancer between 1990 and 1994, those drinking 1 cup of coffee a day were nearly twice as likely to survive 20 years (79%) compared to those drinking 3 or more cups per day (43%). One possible explanation was that coffee consumption “might be a surrogate marker for fatigue.” Fatigue might be an indication of “abnormal proinflammatory cytokine activity” and lead to poorer survival.3
Also in 2013, Maria Simonsson et al, reported that in 310 Swedish women with estrogen receptor (ER) positive breast cancer treated with tamoxifen, drinking 2 or more cups of coffee per day was associated with lower risk of progression over an almost 5-year period. However, the greater the coffee consumption in a total group of 634 women, the more likely that the cancer would be ER-negative.4
In 2015 Ming Ding reported on 3 large American cohorts (the 74,890 women in the Nurses’ Health Study (NHS), the 93,054 women in the Nurses’ Health Study II, and the 40,557 men in the Health Professionals Follow-Up Study) while examining caffeinated and decaffeinated coffee and total and cause-specific mortality. Ding reported that coffee consumption of 1 to 5 cups per day was associated with lower risk of dying, while more than 5 cups per day was not associated with risk of mortality. When data from nonsmokers was segregated, the benefit became clearer: The hazard ratios of mortality were 0.94 (0.89–0.99) for 1.0 or less cups per day, 0.92 (0.87–0.97) for 1.1 to 3.0 cups per day, 0.85 (0.79–0.92) for 3.1 to 5.0 cups per day, and 0.88 (0.78–0.99) for more than 5.0 cups per day (P value for nonlinearity=0.32; P value for trend<0.001).5
In 2017, Susan Gapstur et al estimated hazard ratios for coffee consumption and death from all cancers combined and from specific cancer types among the 922,896 Cancer Prevention Study II participants from 1982 to 2012. Of the 118,738 cancer-related deaths during this time period, there was a nonlinear association between coffee consumption and all-cancer death among current smokers and former smokers and no association among never-smokers. (The once common practice of having a cigarette with one’s cup of coffee has been a recurring problem for researchers as the harmful effects of smoking have clouded over the beneficial effects of coffee in their data.) Among nonsmokers, a 2-cups/day increase in coffee consumption was inversely associated with a small but significant 3% decrease in risk of death from breast cancer (HR: 0.97; 95% CI: 0.94–0.99).6
In 2017, Marc Gunter et al also reported their findings from the 521,330 persons enrolled in the European Prospective Investigation into Cancer and Nutrition (EPIC). During a mean follow-up of 16.4 years, 41,693 deaths occurred. Compared with nonconsumers, participants in the highest quartile of coffee consumption had significantly lower all-cause mortality (men: HR: 0.88; 95% CI: 0.82–0.95; P for trend<0.001; women: HR: 0.93; 95% CI: 0.87–0.98; P for trend=0.009).
Although these researchers reported an increase in ovarian cancer risk (HR: 1.12; 95% CI: 1.02–1.23; P=0.001) in the women, they found no association with breast cancer.7
The new study by Maryam Farvid et al is the most comprehensive of all studies to date in examining this question. The authors account for a growing list of possible contributors to breast cancer risk that have become apparent in recent years and that could have confounded earlier results. We should consider these current findings more accurate than earlier efforts.
These data strongly should, if not directly encourage coffee consumption, at least discourage efforts to wean off coffee. A 24% reduced risk of dying from breast cancer by drinking 2 to 3 cups of coffee a day is in the same ballpark as the benefit gained from undergoing chemotherapy; for most women, doing so would be less onerous. Yet many of these cancer patients come to us attached to the old belief that coffee isn’t healthy and tell us that they are trying to reduce how much they drink.
This new research by Maryam Farvid was done at the Harvard T.H. Chan School of Public Health, and the authors are among the foremost experts in public health epidemiology. If anyone knows how to extract useful knowledge from the massive bank of data collected by the Nurses’ Health Studies, it's them. The list of covariates they took into consideration in analyzing the data reminds us of the history of discovering lifestyle factors that influence breast cancer. There are few risk factors not included that might account for these apparent benefits.
This is far from the first indication that coffee is associated with improved health outcomes. The question as to why so many people still think drinking coffee is an unhealthy habit deserves consideration, not just because encouraging women with a history of breast cancer to drink coffee is an uphill battle but also because this story models the recurring challenge of educating the public in this internet age. Bad news, especially false news, spreads faster, wider, and deeper than the facts based in science.8
The human mind is drawn to pay attention to potential threats. Possible dangers are marked in our awareness as if by flashing neon lights—signs that say, “Pay attention: Look here! Your life depends on this.” Noticing threats, even if false, provides a survival advantage. Our minds are drawn by warnings, and the memory lingers longer.
Coffee has, from its first discovery, raised suspicion. Maybe it is because coffee triggers a similar sensation of heightened alertness as does a perceived threat. Early clerical critics of coffee argued that anything that made one feel as good as coffee does must be bad.
C.W. Post of Grape-Nuts fame deserves some credit for furthering coffee’s negative image. When Post started selling his coffee substitute Postum in 1895 (a few years before he started selling Grape-Nuts and with a recipe some say he stole from Kellogg’s), he promoted the product by extravagantly warning of the dangers of drinking coffee. Many of his false claims have persisted in popular culture. He linked coffee consumption to neurasthenia; today’s equivalent would be like saying coffee causes chronic fatigue or autism.
Bad news about coffee sticks in people’s minds. A 1981 paper suggested that drinking coffee almost doubled risk of pancreatic cancer.9 Although this finding was debunked—the increased risks from smoking were not accounted for—the idea persists, and many of our patients remain certain that coffee causes cancer. California didn’t help matters a few years back when they temporarily ordered coffee shops to label coffee as carcinogenic because it contains acrylamide. Although a scientific review reversed the decision, the message still stuck. Despite the science saying coffee consumption is associated with living longer and healthier lives, the false belief that “It’s not good for you” persists.
One method we might employ to change patient perception is to frequently brew fresh coffee in our offices so that the aroma permeates. A recent study tells us that just the aroma of coffee is enough to have a calming effect and reduce anxiety in patients undergoing dental procedures.10 It’s time to move on from serving herbal teas to brewing coffee. Serving fresh coffee to patients might help them stay awake and pay more careful attention during their visits. It would certainly be one way to start the discussion of the changing science related to coffee.