24th May 2018
This report published today is the third in a series published by the World Cancer Research Fund (WCRF) and American Institute of Cancer Research (AICR). Both the previous reports set out a number of cancer prevention recommendations and these recommendations have been updated in the new report. Also following the 2007 report, the continuous update project (CUP) was set up to provide an ongoing review of the evidence base on diet, physical activity and cancer. The results of the CUP form the basis of this third report.
What has changed since the 2007 report?
While many of the recommendations in the new report are similar to those in the 2007 report, there have been some changes and these are outlined below.
Individual foods and nutrients and their relationship with cancer risk have been reviewed and are summarised in the report. However, WCRF highlight that it is likely that diet and lifestyle patterns, rather than any single factor, work together to increase or decrease the risk of developing cancer. Therefore, they have presented their ten recommendations as an ‘overarching package’, stating that the most benefit is likely to be gained by looking at the recommendations as part of an integrated pattern of behaviours.
There has been an increase in the evidence base on diet, nutrition, physical activity and cancer since the 2007 report including more and bigger cohort studies, an increased number of pooled analyses, more studies considering dietary patterns and more evidence on different cancer subtypes. This increase in the research available for consideration has allowed a more thorough exploration of the relationships between diet, physical activity and cancer, including a greater understanding of thresholds at which an increased or decreased risk is seen and the shape of the dose response. For example, people with lowest consumption of fruit and vegetables have the highest risk of some cancers so it may be more important for those who eat very little or none to have some than for those consuming more than two portions a day to eat more. There is now also more information available on the impact of diet and lifestyle across the life course on cancer risk. Evidence of the effect of diet, nutrition and physical activity in cancer survivors has increased but more is needed.
The Cancer Prevention Recommendations
1. Be a healthy weight
Keep your weight within the healthy range and avoid weight gain in adult life.
- Ensure that body weight during childhood and adolescence projects towards the lower end of the healthy adult BMI range
- Keep your weight as low as you can within the healthy range throughout life
- Avoid weight gain throughout adulthood
The report notes that evidence for body fatness and cancer risk has grown stronger since the previous report. WCRF state that there may be adverse effects specifically from gaining weight in adulthood and also that childhood obesity tends to track into adulthood, which is why a healthy bodyweight in childhood and adolescence is highlighted in the goals.
2. Be physically active
Be physically active as part of everyday life – walk more and sit less.
- Be at least moderately active and follow or exceed national guidelines
- Limit sedentary habits
The CUP found strong evidence for a protective effect of physical activity against several cancers, as well as the potential link between physical inactivity, sedentary behaviour and obesity.
3. Eat a diet rich in wholegrains, vegetables, fruit and beans
Make wholegrains, vegetables, fruit and pulses (legumes) such as beans and lentils a major part of your daily diet.
- Consume a diet that provides at least 30 grams per day of fibre from food sources
- Include in most meals foods containing wholegrains, non-starchy vegetables, fruit and pulses (legumes) such as beans and lentils
- Eat a diet high in all types of plant foods including at least five portions of a variety of non-starchy vegetables and fruit every day
This recommendation was made based on a number of factors. The CUP found strong evidence that wholegrains helped to protect against colorectal cancer. While there was limited evidence for links between specific cancers and certain types of fruit and vegetables, WCRF concluded that the overall pattern of association and the direction of the effect were consistent and so suggested that a protective effect was likely. The report also cited a protective effect of consuming dietary fibre against colorectal cancer as well as weight gain, overweight and obesity.
4. Limit consumption of ‘fast foods’ and other processed foods high in fat, starches or sugars
Limiting these foods helps control calorie intake and maintain a healthy weight.
- Limit consumption of processed foods high in fat, starches or sugars – including ‘fast foods’, many pre-prepared dishes, bakery foods and desserts and confectionery
A recommendation was previously given to avoid high calorie foods and sugary drinks – there is now a separate recommendation on drinks. This recommendation is based on evidence from the CUP that these types of foods could promote obesity, which is associated with greater risk of some types of cancer. WCRF also highlighted a link between high glycaemic load and increased risk of endometrial cancer and in some cases these types of food may have a high glycaemic load.
5. Limit consumption of red and processed meat.
Eat no more than moderate amounts of red meat, such as beef, pork and lamb. Eat little if any processed meat.
- If you eat red meat, limit consumption to no more than about three portions per week. Three portions is equivalent to about 350-500g cooked weight of red meat. Consume very little, if any, processed meat.
This is similar to the previous recommendation to limit red meat and avoid processed meat and the CUP found strong evidence for a positive link between intake of red and processed meat and colorectal cancer. The advice to limit consumption to no more than about three portions per week is new and the figure of 350-500g cooked red meat per week has been developed based on a balance between the potential risks of consuming red meat versus the beneficial nutrients it provides. The report states that the data on processed meat show that even consumption of small amounts appears to increase the risk of colorectal cancer, which is why the advice is to eat ‘little, if any’.
6. Limit consumption of sugar sweetened drinks
Drink mostly water and unsweetened drinks.
- Do not consume sugar sweetened drinks
Having this as a separate recommendation is new in this report although avoidance of sugar-sweetened drinks was previously included along with the recommendation to avoid high-calorie foods. The CUP found strong evidence that consumption of sugar-sweetened drinks caused weight gain, overweight and obesity in children and adults, especially when consumed frequently or in large portions.
7. Limit alcohol consumption
For cancer prevention, it is best not to drink alcohol.
- For cancer prevention, it’s best not to drink alcohol.
The CUP found strong evidence for a link with alcohol and a number of cancers and increased risk was seen at even low levels of consumption. All types of alcoholic drinks had a similar impact on cancer risk.
8. Do not use supplements for cancer prevention
Aim to meet nutritional needs through diet alone.
- High dose dietary supplements are not recommended for cancer prevention – aim to meet nutritional needs through diet alone.
The CUP found that there was strong evidence that high-dose beta-carotene supplements were a cause of lung cancer in smokers and former smokers. In addition, trials with high dose supplements have not consistently shown a protective effect and for most people it is possible to get all the nutrients needed from a healthy diet.
9. For mothers: breastfeed your baby if you can
Breastfeeding is good for both mother and baby.
- This recommendation aligns with the advice of the WHO, which recommends that infants are exclusively breastfed for 6 months and then up to 2 years or beyond alongside appropriate complementary foods.
The CUP found strong evidence that breastfeeding protects the mother against breast cancer and that having been breastfed helps protect children against excess weight gain, overweight and obesity.
10. After a cancer diagnosis: follow our recommendations if you can.
Check with your health professional what is right for you.
- All cancer survivors should receive nutritional care and guidance on physical activity from trained professionals
- Unless otherwise advised and if you can, all cancer survivors are advised to follow the cancer prevention recommendations as far as possible after the acute stage of treatment
The report highlights that people who are undergoing treatment for cancer are likely to have special nutritional needs and that advice from appropriately trained health professionals is essential to support them.
Evidence for the effects of diet, nutrition and physical activity following a cancer diagnosis is limited although there is some research indicating that body fatness and physical activity may predict outcomes in breast cancer. WCRF state that current understanding of the biological interactions between cancer, diet, nutrition and physical activity suggest that the prevention recommendations should be followed where possible and that these may also reduce the risk of other non-communicable diseases.
For more information on WCRF recommendations, click here
BNF has looked at the WCRF 2018 Third Expert Report from the World Cancer Research Fund and how it compares to UK guidelines WCRF/AICR Diet, Nutrition, Physical Activity and Cancer: Third Expert Report from the World Cancer Research Fund in the attachment below.