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 AndrÃ© 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.