Coffee and Cancer – A complicated story

By Michael Edmonds 03/11/2011 7


In last week’s Christchurch Press I noticed an article entitled “Coffee may help prevent skin cancer”. This caught my attention because several years ago I remember reading that coffee contained a wide range of potential carcinogens (cancer causing compounds).

According to the article, women who drank more than three cups of coffee (a day?-time period not specified) had a 20% reduction in risk for basal cell carcinoma while men drinking the same amount of coffee had a 9% reduction. Those drinking the most coffee had even lower levels of risk. Some suggestion was made that perhaps caffeine may play a role.

Looking for more information I found that the World Health Organisation has this year placed coffee on it’s list of group 2B carcinogens – specifying it as a potential carcinogen for urinary and bladder cancer (while noting it may have the reverse effect for bowel cancer).

Further research then lead to a mini-review in Cancer Letters by André Nkondjock of the Research Center for Military Health in Cameroon which suggests that coffee may have some cancer-preventative effects for”liver, kidney, and to a lesser extent, premenopausal breast and colorectal cancers, while it is unrelated to prostate, pancreas and ovary cancers.”

So is coffee cancer causing or does it prevent cancer?

The answer is that it all depends, because this question oversimplifies both cancer and coffee.

Cancer is not a single disease. It occurs in different parts of the body, using a variety of mechanisms, and has genetic as well as environmental contributing factors. Thus it is entirely conceivable that the same compound could inhibit one type of cancer while promoting another. It should also be noted that compounds that might inhibit cancer could even cause other diseases.

Coffee is a complex mix of different compounds, some of which may be carcinogenic, some of which may have preventative effects. Furthermore such effects are likely to be dose dependent – a low dose may have no effect, a higher dose may have a harmful or helpful effect.

This is not to say that such research has no value. On the contrary, observational studies which pick up potential patterns in diseases provide a first step to further investigations of diseases. But one should be very cautious in overreacting to such reports.

liver, kidney, and to a lesser extent, premenopausal breast and colorectal cancers, while
it is unrelated to prostate, pancreas and ovary cancers. Coffee drinking may still help
reduce death due to liver cancer.

7 Responses to “Coffee and Cancer – A complicated story”

  • I always find it interesting when comments are made in the reliability of trials that show a positive influence of a dietary compiling and health, however, if there is a negative association – its more believable…

    One should also be extremely cautious in overreacting to the WHO carcinogen list.

  • Over reaction to/eager reporting of individual studies, resulting in conflicting advice I imagine is one of the things that leads to science getting a bad rap. Grant had a post yesterday – https://sciblogs.co.nz/code-for-life/2011/11/03/trust-science-not-scientists which made a similar point I believe. It’s not the individual study one should be looking at, but the long term trend of studies.

    For example, coffee may have some compounds beneficial in some circumstances, other compounds harmful in other circumstances. You don’t look at a single study that identifies some of the good compounds. Ideally you look at all the studies that have been done on coffee, tally up the good and the bad then make a judgement call and react to it.

    That gets lost when individual studies are reported on sadly.

  • mmm ben.grant…Trust science, not scientists… So how do scientists, who, apparently, shouldn’t be trusted, communicate science????

  • Ron:

    Simple – communicate science. (Think about it.)

    The phrase does not say distrust scientists in the sense you are writing. It says not to confuse individual messengers with the body of scientific work on an issue. You’re confusing the messenger with the message by adding—IMO, trolling with—a false dichotomy.

  • Ben,

    “Over reaction to/eager reporting of individual studies, resulting in conflicting advice I imagine is one of the things that leads to science getting a bad rap”

    Exactly.