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We know that although smoking is still the most important cause of cancer, obesity and high intakes of alcohol increase the risk for several types of cancer. The role of diet in the development of cancer is much less clear, but there is a lot of evidence suggesting that diet does matter.

Q: Translational medicine aims to translate findings at the bench into better treatment for patients. Another way can be to avoid becoming ill. Should today's educational medicine work on prevention rather than a cure?

TK: We definitely need to use both those approaches. For prevention, the first thing is that we need to apply the knowledge we already have better. Probably the most well known example for cancer would be smoking, and smoking rates have come down; lung cancer rates have come down too, so that's great, but there is still a long way to go. More effort is needed applying the knowledge we have. The other thing with prevention is getting more knowledge to allow us to find out other ways of preventing disease. We are talking today about diet and cancer, and that is a prime area where there is a lot of evidence that something is going on, but we haven't yet worked out all the details, and we need to put in the effort and the research to find out what can be done. Coming back to your introduction about cure and treatment, our work on the causes of cancer can relate back to developing treatment, because if you understand the cause of the disease better, that may make it clear where treatment could be applied.

Q: What are the most important approaches that have developed over the past ten years?

TK: In the whole field of diet and cancer the two things that have come through in the last ten years, which are absolutely definitely true and really matter, are that both obesity and high intakes of alcohol increase the risk for several types of cancer; so that is really important information that we have. In terms of other dietary factors a lot of research has been done looking at various foods such as fruit and vegetables, meat, dairy products, and also vitamins and minerals, and the results of that have been much less clear. Two high profile ideas have been that high intakes of meat may increase the risk for bowel cancer, and conversely high intakes of fiber may reduce the risk. But for neither of those is the evidence absolutely clear as to whether they really matter. In terms of the work we are doing here in Oxford, our most exciting area is in hormones, which we have now shown are clearly related to the risk for breast cancer in women and prostate cancer in men, and we are now working at how diet effects levels of hormones.

Q: Does a healthy lifestyle reduce the risk of developing cancer?

TK: Of course it has been known for many years that smoking is the most important cause of cancer, so not smoking is the first thing to do. For people who don't smoke they then have to start worrying about other things, and in terms of lifestyle obesity and alcohol are both important so people should avoid obesity and limit alcohol intake. And there are other things that are also important, like avoiding sunburn and taking up vaccination and screening.

Q: Why does your line of research matter? Why should we put money into it?

TK: The field of diet and cancer has proved more difficult than we thought to sort out, but despite the inconsistencies in the evidence we have at the moment, there is still a lot of evidence suggesting that diet does matter, particularly for some types of cancer such as cancer of the bowel. So we do need to continue this work to sort out what really is true. That may result in being able to give people really strong advice that will have a material effect in reducing their risk of getting cancer. Alternatively it may show that some things just don't matter, and people can stop worrying about certain things that they may or may not want to eat. I'm very optimistic at the moment because the new generation of studies that we now have in place, which are really large to give robust evidence and include things like blood measures as well as dietary questionnaires, should give us much better information than has been available before and allow us to sort out this field.

Tim Key

Cancer, Hormones and Nutrition

Prof. Tim Key is interested in the role of diet and hormones in the development of cancer, particularly cancers of the breast, prostate and bowel. Prof. Key is the principal investigator of the EPIC-Oxford cohort of sixty thousand participants, for various studies on cancer, hormones and nutrition.

This podcast presents the research done by Professor Key whilst working in the Nuffield Department of Medicine. Professor Key now works at the Nuffield Department of Population Health.

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