A Diet to Lower Cancer Risk

(OV secretary Paul Appleby attended the European Conference on Nutrition and Cancer held in Lyon, France, from 21 to 24 June 2001. Here he describes the conference and discusses the latest dietary recommendations for reducing cancer risk. A PDF file containing the abstracts of the lectures and posters from the conference may be downloaded from the conference web site www.nutrition-cancer2001.com)
Organised by the International Agency for Research on Cancer (IARC), part of the World Health Organisation, with the support of the Europe Against Cancer Programme of the European Commission, the European Conference on Nutrition and Cancer attracted more than 350 delegates from throughout the world. There were 40 lectures and more than 130 poster presentations in the impressive Palais des Congres which hosted the conference. The main aim of the conference was to review the scientific evidence on the relationship between nutrition and cancer so as to better understand the causes of cancer and formulate appropriate public health advice.
Some preliminary results from the European Prospective Investigation into Cancer and Nutrition (EPIC) were presented at the conference. The EPIC study involves more than 400,000 volunteers in ten European countries (Denmark, France, Germany, Greece, Italy, Netherlands, Norway, Spain, Sweden and the UK) from whom detailed diet and lifestyle data have been collected. The volunteers are followed-up and the morbidity data subsequently collected are used to investigate associations between diet and lifestyle factors and cancer incidence.
The associations between diet and cancer received widespread publicity with the publication of the World Cancer Research Fund (WCRF) expert report Food, Nutrition and the Prevention of Cancer: a global perspective in 1997. The report was unique in presenting recommendations in terms of both population goals and advice to individuals. Chief among these was the recommendation to eat a plant-based diet rich in a variety of vegetables, fruits, legumes and minimally processed starchy staple foods. If eaten at all, red meat (beef, lamb, pork) was to be limited to no more than 80 grams per day. In essence, plant foods, especially fruits and vegetables, were to be eaten in generous quantities, whereas salted and fatty foods, especially those of animal origin, red meat, and alcohol were to be consumed in limited quantities, if at all. Although the report did not recommend a vegetarian diet as such, vegetarians and vegans could draw comfort from the fact that their own plant-based diets were in generally close agreement with the recommendations. Individuals were also advised to maintain a reasonable body weight, to exercise daily, and to avoid tobacco in any form.
Would the findings presented at the conference support the recommendations of the WCRF report and other expert reports on diet and cancer? The answer turned out to be a qualified "yes". For example, a preliminary analysis of data from the EPIC study found a positive association between the consumption of processed meat and colorectal cancer risk. That is, the greater the intake of processed meat the greater the incidence of colorectal cancer. On the other hand, results from some large dietary intervention studies, in which volunteers follow a diet designed to reduce their cancer risk, have proved disappointing. There are still a lot of lessons to be learned!
So, what are the latest dietary recommendations for reducing cancer risk? A round table discussion on the last day of the conference suggested that Europeans should eat more fruits and vegetables (at least five servings per day), take plenty of exercise (an hour's brisk walk or similar exercise daily), and maintain a healthy body weight (body mass index, calculated by dividing your weight in kilograms by the square of your height in metres, should be between 18.5 and 25). Nothing revolutionary there, but given that most Europeans consume enough food already, which foods should they eat less of in order to make room for the extra fruits and vegetables? Unfortunately, no one was able to provide a satisfactory answer to my question. Vegetarian and vegan diets represent one solution, of course. The avoidance of meat and a greater intake of fruits and vegetables are good reasons why vegetarians might expect to enjoy lower cancer rates than non-vegetarians, although a collaborative analysis of mortality in 76,000 individuals, including 28,000 vegetarians, did not show any significant differences in cancer death rates between vegetarians and comparable non-vegetarians. However, adopting a vegetarian or vegan diet is unlikely to increase your cancer risk, and may confer substantial health benefits, provided that animal foods are replaced with fresh, whole foods rather than denatured, processed foods.

Paul Appleby