Lifestyle changes could cut cancers by a third
More than a third of the most common cancers in developed countries could be prevented by healthy eating and exercise, says a report by the World Cancer Research Fund (WCRF). In developing countries like China and Brazil, it estimates that a quarter of common cancers are preventable.
These figures do not include smoking, which alone accounts for about a third of cancers.
The report, thought to be the most comprehensive ever published on the subject, follows the 2007 release of 10 recommendations on how to avoid cancer. These include avoiding processed meats - including bacon and some sausages - eating less than 6 grams of salt per day, maintaining a healthy weight, and exercising every day.
"People think that somehow cancer comes from heaven, or Darwin, or from their parent's genes, but that's not always the case," says Michael Marmot, chair of the WCRF panel that produced the report. "A third are caused by smoking, and approximately a third are related to diet and physical activity."
To calculate the proportion of preventable cancers, the panel examined the biggest and most reliable studies to date on each of the 10 risk factors, and came up with a relative risk of developing cancer for each one, which would be applicable to people not following the recommendations' advice.
They then estimated the proportion of people in the US, UK, China and Brazil that indulge in this kind of "risky" behaviour.
When they combined the values for the 12 most common cancers, they estimated that 39% of UK cancers are preventable, while 34% of US cancers, 30% of Brazilian cancers, and 27% of Chinese cancers could be avoided.
This means "that there are more actions that could be taken in the UK to reduce cancer than in the US, China or Brazil," says Martin Wiseman, medical and scientific adviser to the WCRF, who adds that consumption of alcohol is a key problem in the UK.
Although a glass or two of wine each day is good for the heart, "over that you get no additional benefit," says Marmot.
The report urges governments across the world to make it easier for people to lose weight and eat healthily, by increasing access to sports facilities and making it safer to cycle to work, and by reducing the cost of healthy foods so people are more inclined to buy them.
"Individuals decide for themselves what to eat, but let's make it easier for individuals and their families to make healthy decisions," says Marmot.
Ten ways to avoid cancer
1. Body fat: aim for a body mass index (BMI) of 21 to 23 and avoid weight gain during adulthood
2. Physical activity: aim for 30 to 60 minutes of moderate physical activity, like brisk walking, every day
3. Junk food: avoid sugary drinks and energy-dense fast food
4. Meat: eat no more than 500 grams of red meat per week and avoid processed meats
5. Alcohol: limit daily intake to one drink for women, two drinks for men. Do not binge drink
6. Fruit and vegetables: eat five portions of fruit and non-starchy vegetables each day and limit refined starchy food
7. Preservatives: avoid salt-preserved foods. Limit salt intake to 6 grams per day
8. Dietary supplements: to be avoided, except in special cases – such as folic acid during pregnancy
9. Breastfeeding: new mums should try to breastfeed for six months
10. Cancer survivors: seek professional nutritional advice