Is a cups of coffee good or bad for your health? This issue has been examined by many studies and this month two interesting studies try again to present the facts.

The first study published in the August 19 online edition of Mayo Clinic Proceedings [1] suggests that drinking more than 28 cups of coffee a week – an average of four cups a day – may lead to an increased risk of all cause mortality. In other words, too much coffee might be a potential killer. The interesting fact in this study, called the Aerobics Center Longitudinal Study, is the size. Data representing 43,727 participants with 699,632 person-years of follow-up were included. Between February 3, 1971, and December 30, 2002 baseline data were collected by an in-person interview on the basis of standardized questionnaires and a medical examination, including fasting blood chemistry analysis, anthropometry, blood pressure, electrocardiography, and a maximal graded exercise test. A cox regression analysis was used to quantify the association between coffee consumption and all-cause and cause-specific mortality.


... Although coffee is a commonly consumed beverage, we have to point out that increasing one’s coffee intake may be harmful...


Younger man and women
The results of the study shows that coffee consumption was positively associated with death in men who drank more than 28 cups of coffee per week (hazard ratio [HR], 1.21; 95% CI, 1.04-1.40). However, after stratification based on age, the results of the study in younger men and women (consuming 28 cups of coffee per week) and death (HR, 1.56; 95% CI, 1.30-1.87 for men; and HR, 2.13; 95% CI, 1.26-3.59 for women) the study authors concluded that people younger than 55 years of age need to avoid heavy coffee consumption. The authors caution that these finding should be assessed in future studies and other populations.

Positive effects of coffee
The second study, published in the August 2, 2013 online edition of Cancer Causes & Control, seems to somewhat contradict the results of the Aerobics Center Longitudinal Study. The unrelated study by scientists at the Fred Hutchinson Cancer Research Center, investigated the association between coffee and tea drinking and reduced mortality from prostate cancer, although the study included too few men who died of prostate cancer to address that issue separately.

Janet Stanford, Ph.D., co-director of the Program in Prostate Cancer Research in the Fred Hutch Public Health Sciences Division, and co-author of the study, conducted the study to determine whether the bioactive compounds in coffee and tea may prevent prostate cancer recurrence and delay progression of the disease.

Stanford and colleagues found that men who drank more than 28 cups of coffee a week – an average of four cups a day - experienced a 59% reduced risk of prostate cancer recurrence and/or progression as compared to those who drank only one or fewer cups per week. The researchers did not, however, find an association between coffee drinking and reduced mortality from prostate cancer, although the study included too few men who died of prostate cancer to address that issue separately.

Assessing the link between tea and prostate cancer outcomes
Regarding tea consumption, the researchers did not find an associated reduction of prostate cancer recurrence and/or progression. The study also did not draw any conclusions regarding the impact of tea drinking on prostate-specific death. “To our knowledge, our study is the first to investigate the potential association between tea consumption and prostate cancer outcomes,” Stanford said. “It is important to note, however, that few patients in our cohort were regular tea drinkers and the highest category of tea consumption was one or more cups per day. The association should be investigated in future studies that have access to larger populations with higher levels of tea consumption.”

Study design
The population-based study involved 1,001 prostate cancer survivors, aged 35-74 years old at the time of diagnosis between 2002-2005, who were residents of King County in Washington State (USA). Participants answered questions regarding their diet and beverage consumption two years prior to prostate cancer diagnosis using a validated food frequency questionnaire, and were interviewed about demographic and lifestyle information, family history of cancer, medication use and prostate cancer screening history.

The scientists followed up with patients more than five years after diagnosis to ascertain whether the prostate cancer had recurred and/or progressed. Those who were still living, willing to be contacted and had been diagnosed with non-metastatic cancer were included in the follow-up effort.

Study results
Of the original 1,001 patients in this cohort, 630 answered questions regarding coffee intake, fit the follow-up criteria and were included in the final analysis. Of those, 61% of the men consumed at least one cup of coffee per day and 12% consumed four or more cups per day.

Prostate cancer-specific
The study also evaluated daily coffee consumption in relation to prostate cancer-specific death in 894 patients using data from the initial food frequency questionnaire. After the median follow-up period of eight-and-a-half years, 125 of the men had died, including 38 specifically from prostate cancer. Daily coffee consumption was not associated with prostate cancer-specific mortality or other-cause mortality, but with few deaths these analyses were limited.

Consistent results
“Our study differs from previous ones because we used a composite definition of prostate cancer recurrence/progression,” noted first author Milan Geybels, a doctoral student at Maastricht University,
Department of Epidemiology, in the Netherlands who was a graduate student in Stanford’s Prostate Studies group at Fred Hutch when the study was conducted. “We used detailed information on follow-up prostate-specific antigen levels, use of secondary treatment for prostate cancer and data from scans and biopsies to assess occurrence of metastases and cause-specific mortality during follow up. Using these detailed data, we could determine whether a patient had evidence of prostate cancer recurrence or progression.”

The results the study were consistent with findings from Harvard’s Health Professionals Follow-up Study, which found that men who drank six or more cups of coffee per day had a 60% decreased risk of metastatic/lethal prostate cancer as compared to coffee abstainers.

Phytochemicals with anti-inflammatory and antioxidant effects
The researchers agree that further research is required to understand the mechanisms underlying the results of the study. The authors confirmed that but biological activities associated with consumption of phytochemical compounds found in coffee include anti-inflammatory and antioxidant effects and modulation of glucose metabolism. These naturally occurring compounds include:

  • Caffeine, which has properties that inhibit cell growth and encourage apoptosis, or programmed cell death. Previous studies have found that caffeine consumption may reduce the risk of several cancer types, including basal-cell carcinoma, glioma (a cancer of the brain and central nervous system) and ovarian cancer.
  • Diterpenes cafestol and kahweol, which may inhibit cancer growth.
  • Chlorogenic acid, which, along with caffeic acid, can inhibit DNA methylation, a biochemical process involved in the development and progression of many cancer types.

Additional studies needed to confirm whether coffee can prevent cancer recurrence

The researchers emphasize that coffee or specific coffee components cannot be recommended for secondary prevention of prostate cancer before the preventive effect has been demonstrated in a randomized clinical trial. Furthermore, there’s ongoing debate about which components in coffee are anti-carcinogenic, and additional large, prospective studies are needed to confirm whether coffee intake is beneficial for secondary prevention.

"Coffee drinking may even be problematic for some men", Geybels noted. "Although coffee is a commonly consumed beverage, we have to point out that increasing one’s coffee intake may be harmful for some men. For instance, men with hypertension may be vulnerable to the adverse effects of caffeine in coffee. Also, specific components in coffee may raise serum cholesterol levels, posing a possible threat to coronary health. Patients who have questions or concerns about their coffee intake should discuss them with their general practitioner,” he explained.

Lack of data
The researchers also noted limits to their study. They point to a lack of data on how coffee consumption might have changed following diagnosis, whether the coffee that participants consumed was caffeinated or decaffeinated, and how the coffee was prepared (espresso, boiled or filtered), a factor that may affect the bioactive properties of the brew.

For more information:
[1] Liu J, Sui X, Lavie CJ, Hebert JR, Earnest CP, Zhang J, Blair SN. Association of Coffee Consumption With All-Cause and Cardiovascular Disease Mortality. Mayo Clin Proc. 2013 Aug 13. pii: S0025-6196(13)00578-8. doi: 10.1016/j.mayocp.2013.06.020. [Epub ahead of print][Article][PubMed]
[2] Geybels MS, Neuhouser ML, Wright JL, Stott-Miller M, Stanford JL. Coffee and tea consumption in relation to prostate cancer prognosis. Cancer Causes Control. 2013 Aug 2. [Epub ahead of print][Article][PubMed]

Photo 1: Janet Stanford, Ph.D co-director of the Program in Prostate Cancer Research at Fred Hutchinson Cancer Research Center. Photo Courtesy: Fred Hutchinson Cancer Research Center/Susie Fitzhugh.  Photo 2: Coffee Beans.  Photo Courtesy/Copyright: Sumatra Anglo Dutch Plantations of Java, Ltd.

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