When it comes to coffee and cancer, there are two questions
which most Canadians want answered: Does coffee cause cancer?
Will drinking coffee help prevent cancer?
As coffee is one of the most studied substances
worldwide, with more than 20,000 studies looking at its general
effects, the coffee and cancer connection has been studied
extensively. Currently, scientists are able to state conclusively
that coffee does not cause cancer with almost universal consensus.
This general consensus is a turnaround from
positions several decades ago, when early studies indicated
that coffee may have cancer-causing properties. However, these
have since been discredited as being poorly designed, not
isolating coffee drinkers from smokers, for example, and essentially
flawed in their conclusions.
As such, upon further view and study, various
international cancer organizations have stated unequivocally
that there is no connection between coffee consumption and
cancer. The Canadian Cancer Society, for example, states that
there is no evidence that coffee or caffeine increases the
risk of cancer.
What's more, evidence is mounting that coffee
consumption appears to have a preventative role in certain
cancers although it is unclear whether this effect is seen
across all types. Numerous credible and well-publicized studies
have concluded that coffee drinkers are less inclined to develop
specific types of cancer, with the most notable evidence mounting
in the following:
The most recognized theory on why coffee
has a role in cancer prevention is that the beverage's high
antioxidant content (link to antioxidant section) is providing
a protective effect. For North Americans, coffee is the largest
daily source of antioxidants, followed by tea and a variety
of fruits and vegetables.
As a major international medical concern, research into understanding
the causes and prevention of cancer is continually evolving.
Countless studies have examined nutritional aspects of prevention,
including how coffee drinkers fare versus non coffee drinkers.
Coffee has emerged as having a potential preventative role
in a number of specific cancers, including the following where
the most compelling evidence has been found:
A large scale study followed 90,000 Japanese subjects over
ten years and concluded that coffee drinkers have half the
risk of developing liver cancer as non coffee drinkers. Published
in the Journal of the National Cancer Institute in 2005, the
study showed this effect for those who drank just one to two
cups daily with the effect increasing at three to four cups(ref)
A Canadian-lead study of 1,700 women with BRCA gene mutations
looked at the effect of coffee consumption and breast cancer
on this group who are already at high risk. For women with
the BRCA1 gene who were also heavy coffee drinkers, averaging
six or more cups a day, results were dramatic with about a
75 per cent reduction in risk of breast cancer. At moderate
coffee consumption levels, results were also promising with
a 10 per cent reduction for one to three cups per day and
25 per cent for four to five cups. The study results were
published in January, 2006 in the International Journal of
Coffee may also help protect against colon cancer, with a
key study showing that three to four cup a day coffee drinkers
cut their risk by 27 per cent versus non drinkers. The Italian
study, published in the International Journal of Cancer in
1997, included controls for smoking, family history, BMI and
diet to effectively isolate coffee's effect.(ref) Another
major study, published in the American Journal of Epidemiology
in 1998 showed similar results with a 28 per cent risk reduction.(ref)
Will drinking coffee cause cancer?
The Canadian Cancer Society advises Canadians that there is
no evidence that coffee or caffeine increases the risk of
cancer. So go ahead and enjoy your daily coffee. In fact,
you might even be doing yourself some good. An emerging body
of evidence is showing that coffee consumption may have a
role in certain types of cancer. For example, studies have
shown that risk of liver cancer may be cut in half for coffee