Nutrition and cancer: recommendations
Based on all the scientific data available, what nutritional recommendations can be given concerning cancer prevention? Faced with the major public health problem of cancer and the plethora of often contradictory views and advice on the subject, ANSES decided to initiate an internal request and published its expert report today entitled "Nutrition and cancer: the soundness of nutritional recommendations for the prevention of cancer" The report clarifies the established levels of scientific proof for a number of nutritional factors that may be involved in the prevention of cancer and provides several recommendations. It emphasises the fact that no single food or nutrient can be considered in and of itself as an "anti-cancer" food.
Cancer is a major public health issue and the number of new cases of the disease increases steadily each year (360 000 new cases in France in 2010). According to the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR), approximately one third of the most widespread cancers could be avoided in the industrialised countries (including France) through nutritional prevention.
To evaluate the soundness of nutritional cancer prevention measures and issue recommendations, ANSES decided to perform a collective expert assessment on the subject. It created a multidisciplinary expert group which met over a four-year period and which based its work as far as possible on studies available worldwide, including in vitro experimentation, animal studies, human epidemiological and clinical data, meta-analyses and international assessments. The group of experts submitted its assessment report in June 2010 to ANSES's expert committee (CES) who then validated it.
This report emphasises the fact that there is no single "anti-cancer" food or nutrient.
Therefore, the consumption of a particular food, nutrient or food supplements is not sufficient on its own to prevent cancers, especially when an individual's diet is generally unbalanced. Over all, to reduce the risk of excesses or deficiencies in particular foods or nutrients and therefore prevent cancer risks, a balanced and varied diet is recommended along with a caloric input adapted to energy expenditure and regular physical activity, in compliance with the recommended dietary reference intakes.
The report is consistent with the conclusions of international studies in this area. It reasserts that cancers are complex diseases resulting for the interaction of a large number of factors, including genetic factors specific to each individual, behavioural factors (smoking, physical activity, etc.) and general environmental factors, including diet.
A report that confirms current recommendations
The nutritional factors influencing the risk of cancer may have different mechanisms of action:
- a direct effect from food via excess or deficient intake of specific nutrients or foods;
- an indirect effect of food: the development of an overweight or obese condition that may cause the disruption of normal body function (hormonal in particular);
- an indirect effect of physical exercise which affects the hormones and promotes caloric balance.
The expert assessment has identified eight nutritional factors which have a clear or probable effect on cancer risk and for which specific nutritional recommendations for the French population have been issued. With regard to each of these factors, ANSES has analysed several criteria, including population exposure (dietary habits, prevalence of overweight and obesity, a sedentary lifestyle, etc.) and the frequency of the types of cancers linked to these criteria in France.
ANSES mentions that it is therefore recommended to limit consumption of high calorie foods since they increase the risk of becoming overweight. Furthermore, alcoholic beverages should be limited as well as red meat, delicatessen meats and salty foods, all of which play a role in the onset of certain types of cancer. It is therefore important to note that although salt consumption has decreased somewhat in the last few years, the average intake (8.5 g per day for an adult) remains excessive in France.
It is also recommended to favour fruits and vegetables which play a major role, second only to cereals, in providing the required vitamins, minerals and fibres, and to reducing the caloric density of the diet. However, the average intake of fibres in France (18 g/d) remains well below the French Population Reference Intake (ANC) (30 g/d for an adult).
Other recommendations:
Smokers should avoid talking food supplements containing beta-carotene because it has been found to increase the risk of lung cancer in this group.
Breastfeeding exclusively through the age of 6 months is recommended, for women who wish to do so, due to the benefits of this practice for both mother and baby.
Physical activity equivalent in intensity to a brisk walk, at least 30 minutes a day and 5 days a week, makes it possible to control weight gain and limits the risk of cancer.
This study supports existing recommendations (French National Plan for Nutrition and Health [PNNS], cancer plan) in favour of a varied diet and moderation regarding certain foods. These recommendations are compliant with those issued by more general nutrition campaigns which aim to prevent overweight and obesity as well as cardiovascular disease.
In order to reinforce current knowledge and to fill in certain gaps in understanding that were pinpointed during this study, ANSES has also issued a series of recommendations regarding research.