Report links obesity to risk of developing aggressive prostate cancer

The World Cancer Research Fund has published a report showing that men who are overweight or obese are at more risk of developing an advanced or aggressive form of prostate cancer than men of healthy weight. They’ve also estimated that around 10 per cent of the men diagnosed with advanced prostate cancer in the UK each year could be prevented from developing it, if they kept to a healthy weight.

This is one of the most in-depth reviews of the links between diet, lifestyle and prostate cancer risk that’s ever been carried out. It was done by analysing the results of over 100 other research studies, which together involved more than 9.8 million men including 191,000 men with prostate cancer.

The report has found clearer links than have been spotted before between prostate cancer and waist size and BMI (a measurement used to indicate when someone is over or underweight). However, what's also interesting about it is that it’s muddied the waters a bit when it comes to the links between prostate cancer risk and certain types of food.

Some of the results haven’t changed since the last report was published in 2007. For example, they still consider that there’s strong” evidence that beta-carotene – either from foods like carrots or sweet potatoes, or from supplements – is unlikely to affect a man’s risk of getting prostate cancer. There is also evidence linking a diet high in dairy products, or low levels of vitamin E in the blood, to increased prostate cancer risk – but that evidence is “limited”.

On the other hand, the sheer volume of research that’s been carried out into lifestyle and prostate cancer over the last seven years means we now know that not all prostate cancers are the same, and most new studies concentrate on subtypes of prostate cancer (such as advanced or localised prostate cancers), rather than grouping them all together. This means that the conclusions we can draw from these types of studies are more complicated and less black-and-white than they may have seemed before.

That’s why some of the other findings about dietary risk factors for prostate cancer have changed since the 2007 report. The report’s authors have downgraded evidence linking diets high in calcium to an increased risk of prostate cancer from “strong” to “limited”. They also downgraded evidence that foods containing lycopene (such as tomatoes) decrease the risk of prostate cancer, from “strong” to “no conclusion possible”. And they have downgraded to “limited” the evidence linking low blood-plasma levels of selenium to increased prostate cancer risk

This study highlights what we’ve said before – that diet is complicated.  It’s very difficult to see patterns and draw conclusions between individual parts of a man’s diet and his risk of developing prostate cancer. But eating a healthy, balanced diet is a good idea – and not just when it comes to prostate cancer risk.

Dr Matthew Hobbs, Deputy Director of Research at Prostate Cancer UK summed up the important points of this reportnicely when he said: “Maintaining a healthy weight and staying active can protect against many diseases, including cancer. The link found in this research between being overweight and risk of aggressive and advanced prostate cancer is an important finding.

“Prostate cancer often has no symptoms in the early stages when it is most treatable and so awareness of risk is crucial.  We already know that men over 50, Black men and men with a family history of prostate cancer are more likely to develop the disease. This report shows there is growing evidence that BMI and waist size may be another tell-tale sign. Importantly, unlike other known risk factors, this is something that men can do something about.”

“The current process of diagnosing prostate cancer fails to distinguish aggressive from harmless forms of the disease so GPs have to decide whether it’s worth a man being tested. We must get to a point where doctors can identify and test those men who are most likely to develop aggressive disease, while sparing others unnecessary treatment. This research may give doctors an important new warning to look out for.”