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Coffee Consumption and Cancer: Another Shot across the Bow
Abstract & Commentary
By Robert L. Coleman, MD, Professor & Director, Clinical Research, Department of Gynecologic Oncology, University of Texas, M.D. Anderson Cancer Center Department of Gynecologic Oncology, Houston, is Associate Editor for OB/GYN Clinical Alert.
Dr. Coleman reports no financial relationship to this field of study.
Synopsis: This new study suggests coffee consumption may reduce endometrial cancer risk effect, independent of caffeine.
Source: Hirose K, et al. Coffee consumption and the risk of endometrial cancer: Evidence from a case-control study of female hormone-related cancers in Japan. Cancer Sci. 2007;98:411-415.
Worldwide, coffee is a popular beverage used daily with increasing frequency. Caffeine, a dominant ingredient, has been implicated in many conditions including hormonally active cancer (due to its impact on sex hormone binding globulin [SHBG] homeostasis). Confusingly, this effect has been documented to be both detrimental and beneficial under different conditions and in different models. Epidemiologically, the relationship between coffee consumption and cancer has also been inconsistent. To evaluate the impact of coffee and caffeine consumption on hormone-related cancers, Hirose and colleagues interrogated data from a hospital-based epidemiological study of women presenting for a first visit. They designed a case-control study where cases were women identified at first visit with breast, ovarian or endometrial cancer. Controls were unaffected individuals. All subjects were queried for use of coffee and other beverages potentially containing caffeine such as green and black tea. Detailed anthropomorphic and reproductive information was additionally recorded. The investigators demonstrated a protective effect of coffee, but not caffeine on the occurrence of endometrial cancer. In addition, there was a significant trend to greater effect by higher coffee consumption; the reduction in the odds for endometrial cancer was 59% among those women consuming 3 or more cups per day. No relationship was seen for breast or ovarian cancer. However, there was a protective effect of caffeine on ovarian cancer incidence. No other relationships were identified with breast or endometrial cancer. The authors conclude that coffee consumption has a protective effect, independent of caffeine in endometrial cancer risk. However, the inconsistent effect on other hormonally sensitive tumors requires further investigation to elucidate the pathobiology of coffee and its components on cancer risk.
Almost as certain as death and taxes is an investigation attempting to link (positively or negatively) coffee consumption to the development of disease. There have been many targets over the years, including coronary artery disease, Alzheimer's disease, miscarriage, gall bladder disease, chronic liver disease, not to mention the cancers such as hepatocellular carcinoma, bladder cancer and those addressed in this current study. Indeed, a search of "coffee" and "cancer risk" returns more than 550 citations in MedLine. The relationship is complex as caffeine, a primary constituent, is an active and "desired" compound that has known biological activity. However, there are other components to the beverage, such as polyphenols (antioxidants), which are far less studied but may be equally responsible for the observations confusing the many investigations. In this current study, the author opined that coffee consumption could positively impact circulating estrone and SHBG to potentially reduce the risk of endometrial cancer. Such a relationship has been observed in a cross-sectional study of US women linking the effect to caffeine intake. However, in a case-control study conducted in Hawaii, no effect was observed.
The current study was conducted based on detailed questionnaire data obtained from women who sought medical attention at a large central hospital. While hospital-based analytical studies are frequently biased by selection of sicker patients, women in Japan frequently seek hospitals as a first visit—similar to a practitioner's office in the USA, and more typically represents the population at large. A little more than 2500 cancer cases were compared against 12,425 controls. Other associations noted among coffee drinkers were higher rates of smoking and alcohol use, and lower fruit intake. They also tended to be younger and thinner. Although obesity is associated with lower levels of SHBG, the investigators could not demonstrate a protective effect with coffee consumption in their "obese" cohort—defined as a BMI of 22 or greater. This suggests the effect of coffee consumption on SHBG could not overcome the reduction seen in this cohort. Nonetheless, controlling for these and other confounding variables they were still able to link coffee, but not caffeine, to reduced risk of endometrial cancer. This suggests the association is due to other components of coffee, such as the antioxidants. Of interest, other polyphenols, such as resveratrol and gallic acid, are entering clinical investigation as single agents and in combination other therapies due to their ability to scavenge free radicals.
As an avid consumer of this "health" product, I am relieved another salvo has been turned back. However, it is clear more work is necessary to determine the true heath impact of this common beverage on a wide variety of disorders.