Modifying cancer risk through diet

According to research from late last year, almost 40% of annual cancer deaths in Australia are potentially preventable. While tobacco smoking is still the headline risk factor, accounting for 23% of all cancer deaths, poor diet and overweight and obesity are becoming increasingly significant, each contributing to about 5% of cancer deaths.
 
‘Diet is also not just a direct risk factor, but indirect as well, through overweight and obesity,’ Professor Mark Harris, GP and main author of the RACGP’s SNAP (smoking, nutrition, alcohol and physical activity) guide, told newsGP. ‘If you include alcohol as part of the diet, then there’s an even wider range of cancers that are involved.’
 
Research has shown that Australians tend to fare poorly when it comes to having a good diet.
 
‘Many of us don’t eat enough fruit and vegetables, or enough fibre,’ Professor David Whiteman, Senior Scientist and Deputy Director at QIMR Berghofer Medical Research Institute, told newsGP. ‘All of those factors are protective against many kinds of cancer, particularly cancers of the bowel and the intestinal tract.
 
‘Also, our consumption of red meat is amongst the highest in the world and, when eaten in excess, red meat is known to cause cancer of the bowel.’
 
There are also differences in cancer risk between genders. It is estimated almost 75,000 men will be diagnosed with cancer in Australia in 2018, compared to around 63,670 women. Professor Whiteman believes much of this can be attributed to gendered lifestyle differences.
 
‘The proportions of potentially preventable cancer deaths are higher among men than women because, on average, men smoke and drink more, spend more time in the sun, and don’t eat as well,’ Professor Whiteman said.
 
However, Professor Harris is not so sure the evidence shows that men have a significantly poorer diet than women, although he does identify other differences that may have an effect on their cancer risk.
 
‘Men do consume more calories and more saturated fat and meat, and this contributes to higher overweight and obesity levels,’ he said. ‘They also consume much more alcohol, which is a potent carcinogen.’
 
Professor Harris is keen to emphasise that diet is not the only factor in rates of overweight and obesity.
 
‘Looking at the rates of physical activity between males and females, there’s not really much difference at all. It’s equally bad,’ he said.
 
Regardless of such differences, diet remains a significant – and modifiable – factor in cancer risk that can be addressed in general practice.
 
‘We can encourage people to be mindful of how much alcohol they consume, how much they weigh and how much exercise they get,’ Professor Whiteman said. ‘That’s not to say if people follow those goals, they’ll never get cancer; we can’t prevent all cancers.
 
‘But it can reduce the numbers of cancers that are occurring at a level in the population.’
 
Professor Harris would like to see better tools made available to help GPs address dietary risk factors in consultations.
 
‘We’ve already got risk calculators for things like heart disease risk and stroke,’ he said. ‘We need some tools like that so you can sit down with a patient and say, “Your BMI [body mass index] is 31, you’ve got a poor diet and not enough physical activity, and this is what that’s likely to do in terms of your risk of various cancers”.
 
‘Those tools are available in the UK, but they’re not yet fully available in Australia. It would be useful to have those, to start that conversation. We really want to help people do all they can to prevent cancer.’

cancer-and-diet cancer-risk-factors overweight-and-obesity snap-guide