Coffee consumption may reduce endometrial cancer risk
Coffee consumption may reduce the risk for endometrial cancer, according to a study published in The Journal of Obstetrics and Gynaecology Research.
Yu Gao, of the departments of obstetrics and gynecology at Liangxiang Hospital of Beijing Fangshan District and at Peking Union Medical College Hospital, both in Beijing, and colleagues reviewed 24 observational studies that included 9,833 incident cases of endometrial cancer and 699,234 patients.
There were 12 case-control studies (4,022 cases; 19,839 subjects) and 12 prospective cohort studies (5,811 cases; 679,395 subjects) investigating the association between coffee consumption and the risk for endometrial cancer.
The pooled RR of endometrial cancer was 0.71 (95% CI, 0.65-0.77) for the highest vs. the lowest categories of coffee intake. The case-control studies had a pooled RR of 0.68 (95% CI, 0.56-0.83), and the cohort studies had a pooled RR of 0.7 (95% CI, 0.63-0.77).
Europe and the United States/Canada had similar pooled RRs of endometrial cancer of 0.74 (95% CI, 0.62-0.88) and 0.71 (95% CI, 0.64-0.79), respectively, but Japan had a pooled RR of 0.4 (95% CI, 0.28-0.57). The researchers attributed these differences to varying genetic backgrounds, lifestyles, dietary patterns and endometrial cancer incidences.
In the six studies on different types of coffee, caffeinated coffee had a pooled RR of 0.66 (95% CI, 0.52-0.83), and decaffeinated coffee had a pooled RR of 0.86 (95% CI, 0.71-1.04). The researchers noted that caffeine intake may directly affect sex hormone binding globulin levels, inhibiting the risk for endometrial cancer.
In two studies, the researchers found a pooled RR for filtered coffee of 0.77 (95% CI, 0.38-1.53) and 0.56 (95% CI, 0.3-1.04) for boiled coffee, leading them to suggest there was no significant association between cancer risk and how the coffee was made.
Eight studies that looked at coffee, BMI and endometrial cancer risk found a pooled RR of 0.65 (95% CI, 0.54-0.79) for higher BMI and 0.88 (95% CI, 0.75-1.03) for lower BMI. The bioactive components in coffee benefit metabolism, the researchers said, and these benefits are more obvious in women with a higher BMI.
In six studies, there was a pooled RR for endometrial cancer of 0.56 (95% CI, 0.45-0.7) among coffee drinkers who had smoked at some point and 0.68 (95% CI, 0.56-0.84) among those who had never smoked.
The researchers noted potential synergy between the bioactive ingredients of both coffee and cigarette smoke in endometrial carcinogenesis, as the same family of cytochrome P450 enzymes metabolizes caffeine, nicotine and estrogen molecules.
Finally, in three studies, the pooled RR was 0.88 (95% CI, 0.79-0.98) for coffee drinkers who never used hormone replacement therapy and 0.97 (95% CI, 0.92-1.02) for coffee drinkers who had.
The researchers said estrogen exposure is an important risk factor for endometrial cancer, and that coffee’s protective effect would be more significant in a low-estrogen environment.
The inverse association between high coffee consumption and the risk for endometrial cancer was significant among the cohort and case-control studies alike, especially for caffeinated coffee, suggesting a protective link, they concluded.
Perspective
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Endometrial cancer is the most common gynecological cancer. In 2021, there were approximately 67,000 new cases of uterine cancer diagnosed in the U.S. Endometrial cancer is also the gynecologic cancer with the clearest symptom—postmenopausal or abnormal uterine bleeding.
Therefore, in some ways, it is our easiest cancer to “catch” early in the disease process. Symptom awareness is critical, empowering women to seek care and achieve earlier diagnosis. Fortunately, endometrial cancer is treatable, with more than 80% of endometrial cancer patients surviving five years.
Despite this favorable scenario, endometrial cancer is one of the rare cancers where mortality is increasing over time. Between 2010 and 2019, mortality has been rising an average of 1.7% each year. In 2021, this amounted to almost 13,000 deaths. The reasons why are multifactorial and complex, and we are working on identifying them, as well as interventions to reverse the trend.
We know that there are modifiable risk factors for the development of endometrial cancer. Obesity is a core risk factor for the development of endometrial cancer. Therefore, diet, exercise and effective treatment of diabetes and other underlying medical conditions all decrease risk of endometrial cancer. In the U.S., we are seeing rising incidence of obesity, and that may be linked to some of what we are seeing in endometrial cancer incidences and mortality.
This article emphasizes an element of diet—caffeine intake. The medical literature continues to point to caffeine as something that may decrease the risk of endometrial cancer. But in many ways, it’s a broader point about the risks of endometrial cancer related to obesity, nutrition and diet that we should walk away with, more than the specifics of caffeine itself.
The typical, most common type of endometrial cancer is related to excess estrogen in the body. So, anything that modulates the degree to which estrogen is circulating in the body will impact risk. That’s why obesity and diabetes are important.
The problem with any study that looks at an element of dietary intake such as caffeine or alcohol or fat or sugar is that they are lifetime additives, not single intervention points. That makes it very hard to track and establish causation.
Today, I don’t ask my patients about their caffeine intake, and I would not say that I have a lot of anecdotal experience to say that my patients who drink a lot of coffee or tea have less endometrial cancer than those who don’t.
Instead, we focus more on menstrual history, pregnancy, prior use of hormone replacement therapy, diabetes, obesity and prior use of medications such as tamoxifen. There are many risk factors and elements of a medical history that we ask about in the context of a new diagnosis of endometrial cancer for almost all patients as part of our evaluation.
While we do not yet have enough information from this study, or from other studies, to be able to integrate a caffeine history into clinical care as a standard practice, the repeat findings of a link between caffeine and cancer risk remain intriguing and thought-provoking. It once again emphasizes that cancer, its risk factors and ways to change those risks, are incredibly complex.
We need to rely on larger studies to map out biologic plausibility and implications. Then we can see if there is any potential for intervention moving forward or for better advice to give about the implications of our patients’ daily cup of joe.
Perspective
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The findings presented in this paper are in line with published studies that have attempted to evaluate the role of coffee consumption and endometrial cancer. We do see a consistent trend with coffee consumption and a possible reduced risk of endometrial cancer. However, the available studies are very limited due to potential bias.
Bias means there are variables in the studies that may not fully explain if coffee is the main driver for reduction in endometrial cancer risk. We cannot draw conclusions regarding the amount of coffee, the type of coffee (caffeinated or not) or the type of endometrial cancer that is impacted.
In my own practice, use of coffee does not play a direct role in counseling of patients regarding endometrial cancer risk reduction. We discuss healthy lifestyle with use of fruits, vegetables and a Mediterranean diet where feasible. We know that obesity and large amounts of processed foods are associated with cancer.
I encourage patients to exercise and consider meeting with a nutritionist to discuss healthy changes to their diet. If someone wants to drink coffee, I think that is very reasonable. I would not recommend it alone to reduce endometrial cancer risk given the lack of quality studies (studies without bias).
The results of this study do not directly improve patient care currently. Coffee can be used by patients, but anything that is done to an extreme may be harmful in one's diet. I recommend moderation and incorporating coffee in one's lifestyle in a manner that includes healthy living (exercise, diet) if that person enjoys coffee. I would not seek coffee out solely to reduce the risk of endometrial cancer.
Further evaluation in specific patient populations will be needed to better understand how much coffee per day and what type of coffee (ie, what components) do impact endometrial cancer risk.
Patients should talk with their doctors about their own individual risks for endometrial cancer. This includes family history, diet, use of hormone replacement therapy and other medical conditions such as diabetes. There are many direct steps someone can take to reduce their risk of endometrial cancer. Engaging with your medical team and taking ownership of one's health is the best approach.
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