Every cup of coffee you drink diminishes your chances of prostate cancer (a little)
Coffee protects men against prostate cancer. Every cup of coffee that men drink per day reduces their chance of developing prostate cancer by 1-3 percent. Researchers at the Nanjing Medical University in China calculated this in a meta-study published in the European Journal of Clinical Nutrition.
Prostate cancer & coffee
Men with prostate cancer have a better prognosis if they have drunk large amounts of coffee previously read posts on websites in response to an epidemiological study published in Cancer Causes and Control. [Cancer Causes Control. 2013 Nov;24(11):1947-54.]
The media is now littered with these news items, each one offering a different point of view. Today coffee is healthy; tomorrow it's bad. But according to the Chinese meta-study, that coffee offers men protection against prostate cancer is now an established fact. It's the largest meta-study on the effects of coffee on prostate cancer that has been published so far.
The researchers gathered data from 24 studies and re-analysed them. They noticed that case-control studies carried out in hospitals tended to conclude that coffee increases the chance of developing prostate cancer.
But these kinds of studies are not wholly reliable: they compare men who have prostate cancer with men who don't. It's likely that men with prostate cancer exaggerate the amount of coffee they drink when filling in dietary questionnaires because they suspect that there's a relationship between their disease and their coffee consumption.
More reliable studies - in which researchers monitor the dietary behaviour of healthy men and follow them for many years so they can see who develops prostate cancer and who doesn't - show that coffee reduces the likelihood of developing prostate cancer. These studies are called cohort studies.
When the Chinese had gathered all their data, they found that men who drank one or two cups of coffee daily - the moderate coffee drinkers - were less likely to develop prostate cancer than the men who never or only rarely drank coffee. The figure below shows this.
However, men who drank relatively large amounts of coffee – four cups a day or more – were even better protected against prostate cancer.
For each cup of coffee the men drank per day, their chance of developing prostate cancer decreased by a few percent, the researchers discovered.
The researchers don't know exactly how the protective effect of coffee works. One possibility is that the caffeine in coffee causes prostate cancer cells to commit suicide. Another possibility is that the antioxidants in coffee prevent healthy prostate cells from mutating into prostate cancer cells.
In 2013 the same researchers published a meta-analysis in PLoS One in which it appeared that coffee has a minimal protective effect against breast cancer in women. [PLoS One. 2013;8(1):e52681.]
Eur J Clin Nutr. 2014 Mar;68(3):330-7.
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