The apparent benefit was limited to regular coffee, as consumption of decaffeinated coffee was associated with only a trend toward an inverse relationship with endometrial cancer risk, as reported online in Cancer Epidemiology, Biomarkers & Prevention. Tea consumption was not associated with the risk of endometrial cancer in this study.
“Our findings provide prospective evidence with the potential beneficial role of four or more cups of coffee per day against endometrial cancer risk,” Youjin Je, MS, of Harvard School of Public Health in Boston, and co-authors wrote. “However, recommendations about high coffee consumption should be made with caution. Because our population is relatively health conscious and thus may tend not to add substantial sugar and cream, the results of risk reduction with four cups of coffee per day may not be generalizable to coffee drinkers who typically add sugar or cream to coffee.”
In theory, coffee consumption might influence endometrial cancer risk via caffeine’s effects on the female hormonal milieu. Studies have shown that coffee or caffeine intake influenced levels of sex hormone binding globulin, free estradiol, C-peptide, and adiponectin, the authors wrote in their introduction.
Epidemiologic studies have demonstrated an inverse association between coffee consumption and endometrial cancer risk, but most of the data was collected retrospectively. Moreover, few studies attempted to control for caffeine intake or coffee components that might influence endometrial cancer risk.
The prospective Nurses’ Health Study (NHS) provided a dataset with characteristics that could address limitations of previous investigations of coffee consumption and endometrial cancer, the authors continued. Initiated in 1976, the NHS accumulated data on 121,700 female nurses who were ages 30 to 55 at enrollment.
Je and colleagues analyzed data on a subgroup of 67,470 Nurses’ Health Study (NHS) participants who completed an initial food frequency questionnaire in 1980 and six follow-up questionnaires until 2002. In a complicated analysis, the inverse association no longer remained significant for other variables except for the comparison of four or more cups of coffee daily versus less than one cup daily.
Analysis of the type of coffee consumed showed that women who drank four or more cups of caffeinated coffee daily had higher reduction in relative risk than women who drank less than one cup daily. Increasing consumption of decaffeinated coffee was associated with a nonsignificant reduction in the relative risk of endometrial cancer.
“Unmeasured factors associated with coffee drinking habit may also have influenced our results. However, the factors are more likely to be related to unhealthy lifestyles rather than healthy lifestyles, which make the observed association more inverse after adjusting for the factors.”
The study was supported by the National Institutes of Health.
Primary source: Cancer Epidemiology, Biomarkers & Prevention