Bioactive compounds in coffee may have anti-inflammatory and antioxidant effects
SEATTLE – Aug. 26, 2013
Coffee consumption is associated with a
lower risk of prostate cancer recurrence and progression, according to a
new study by Fred Hutchinson Cancer Research Center scientists that is online ahead of print in Cancer Causes & Control.
Corresponding author Janet L. Stanford. Ph.D., co-director of the Program in Prostate Cancer Research in the Fred Hutch Public Health Sciences Division, 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 four or more cups of
coffee per 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.
They 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.
First study to assess 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,” the authors wrote. “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.”
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, Wash. 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 researchers 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.
Of the original 1,001 patients in the 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 the highest amount:
four or more cups per day.
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.
“Our study differs from previous ones because we used a composite
definition of prostate cancer recurrence/progression,” said first author
Milan Geybels, a doctoral student at Maastricht University 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 are 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 in coffee have anti-inflammatory and antioxidant effects
Further research is required to understand the mechanisms underlying
the results of the study, 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. Further, 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 said.
“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. Or, 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 said.
The investigators also noted limits to their study, which included 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.
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