New report gives definitive cancer risk information
31 October 2007
A major new report by the World Cancer Research Fund International, led by Professor Sir Michael Marmot, UCL Epidemiology & Public Health, is released today, shedding new light on how lifestyle affects the risk of cancer.
The Second Expert Report examined all the available research relating to cancer prevention from around the world over the last five years. It is the most authoritative report ever to be published on the subject of food, nutrition, physical activity and the prevention of cancer.
The publication follows the first Expert Report, which was produced ten years ago. The new results show that some cancer risks are now more fully shown by the evidence than they were previously. The new report also mentions breastfeeding for the first time.
Among the report's findings are some facts that people may not have been aware of. Professor Marmot stressed the need for people to stay within the healthy range (18.5 to 25) for body mass index (BMI - your weight in kilos divided by your height in metres squared). For cancer prevention, people need to aim for the lower end of this range. Professor Marmot, speaking to journalists about the report this morning, used models to illustrate what the upper and lower end of this range looks like. Often the media only portrays extremely fat people when discussing obesity and overweight, when in fact people at the top of the 'healthy' BMI range can also have a heightened risk of cancer.
Professor Marmot said: "If that sounds more drastic and tougher than the advice about weight you've heard from health organisations before, that's because it is. In fact, it's a considerably stronger recommendation than we ourselves made in our first Expert Report." The report also states that where on the body excess fat is stored is very important - excess weight stored around the waist is the most dangerous as it increases the levels of some hormones in the bloodstream that are linked to cancer.
Another conclusion drawn from the report was that it is 'convincing' that people who eat more than 500g of red meat in a week increase their risk of colorectal cancer. Previously this risk was believed to be 'probable'.
Smoking was one area the research did not focus on. However, Professor Marmot stated at the beginning of his presentation: "Pretty much the most important thing you can do to prevent cancer is not to smoke."
The report makes ten key recommendations for reducing the risk of cancer. These are:
- 1) Aim to have a body mass index within the range of 18.5 to 25. Also, within that range, try to stay as lean as possible. The report found that being overweight and obese increases your risk for more types of cancer than was previously thought. It is important to avoid putting on weight or increasing your waist measurement throughout your adult life. Many people put on weight steadily as they grow older.
- 2) Aim to do one hour's moderate exercise, or half an hour's vigorous exercise, every day. The research found that physical activity in its own right reduces the risk of colorectal cancer, and probably also protects against post-menopausal cancer and endometrial cancer - as well as reducing other risks such as heart disease.
- 3) Limit energy-dense food, and avoid sugary drinks. The report points out that fruit juice contains as much sugar as fizzy drinks, although they also contain vitamins and minerals, so should be limited to one glass a day.
- 4) Eat at least five portions of a variety of vegetables and fruit every day, and try to eat unprocessed grains and beans with every meal. The rule of thumb is to try to make sure that in every meal at least two thirds of the plate is filled with plant foods such as vegetables, fruit, whole grains and beans.
- 5) Limit your intake of red meat (lamb, pork and beef) to 500g a week, and avoid processed meat (bacon, ham, hot dogs and some sausages). Above 500g the risk of colorectal cancer is clearly seen to rise.
- 6) In terms of cancer, even small amounts of alcohol should be avoided. However, modest amounts of alcohol can reduce the risk of heart disease, so the recommendation of the report is to limit alcohol intake to no more than one drink a day for women and two for men.
- 7) Limit salt to 6g a day.
- 8) Do not use dietary supplements to protect against cancer. It is unclear whether people get the same benefits from nutrients if they are taken in supplement form, and too much could be harmful to health. A balanced diet will provide all the nutrients we need.
- 9) New mothers should breastfeed exclusively for the first six months, and then add other liquids and foods. This is the first cancer report ever to touch on breastfeeding
- 10) Anyone who has cancer should seek professional nutritional guidance from the moment they are diagnosed, and cancer survivors should follow the above recommendations after their treatment is completed.
Professor Jane Wardle, Director of the Cancer Research Health Behaviour Unit at UCL Epidemiology & Public Health, said: "The WCRF report draws together the wealth of scientific evidence that lifestyle is overwhelmingly important in the risk of getting cancer. The 10 recommendations on diet, physical activity and weight take us a step further than those of the 1997 report, and are presented in a way that translates science into action. Cancer prevention is one of the highest health priorities, and this report shows that if the research community, the public, government, and industry pull together, we will make progress."
To find out more about the World Cancer Research Fund, follow the links at the top of this article.