Cancer epidemiologist Brian Cox, from the University of Otago, talks about studying the causes of cancer and new research on diet and bowel cancer.

A new study from cancer epidemiologists at the University of Otago reveals that eating dairy products and a low-fat diet can reduce the risk of bowel cancer.

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Diet has long been known as a risk factor for bowel or colorectal cancer, but the new study, by Mary Jane Sneyd and Brian Cox, from the Hugh Adam Cancer Epidemiology Unit at the Otago Medical School, is the first to specifically examine the role of diet as a cause of bowel cancer in New Zealand.

The report showed that "higher than average" consumption of lamb, pork and bread and processed meat such as salami and sausages, was associated with an increased risk of bowel cancer.

For the first time it was found that dairy products - but not cheese - and a low-fat diet were associated with a reduced risk, which may offset the elevated risk from meat consumption.

A reduced risk of bowel cancer was also found with a history of vigorous exercise.

"There are several risk factors for bowel cancer and their relative contribution to the disease differs among countries and between regions within countries," says Brian.

"Therefore, the prevention of bowel cancer here requires New Zealand specific knowledge of the relative contribution of the risk factors for bowel cancer, which is vital for the control of bowel cancer in New Zealand.

Contrary to previous research, this study found greater than average consumption of fresh fruit or vegetables did not significantly reduce the risk of bowel cancer and no reduced risk was found for vegetarians or vegans.

The case control study drew on data from the New Zealand Cancer Registry, and questionnaires completed by 806 bowel cancer patients, aged between 30 and 74-years-old and 1025 people matched as controls.

Brian says that New Zealand has very high rates of bowel cancer, although rates vary considerably by birth year. People born between 1940 and 1956 have less than half the rate of bowel cancer compared to people born earlier. But since 1956 rates have risen again.

Listen to the full podcast to hear Brian talk about cancer epidemiology and why it is important to investigate the causes and risk factors associated with cancer, as well as the effectiveness of various screening and treatment programmes.

You can listen to Brian Cox and Mary Jane Seyd talk about melanoma in an earlier Our Changing World interview.

Go to this episode on rnz.co.nz for more details