World Cancer Research Fund’s Cancer Prevention Recommendations are generally relevant worldwide. However, some findings of the Continuous Update Project were not suitable for inclusion in the global Recommendations even though the Panel judged the evidence to be strong.
There are four main reasons why:
- The exposure is a public health issue that people cannot necessarily influence themselves (height and birthweight, arsenic in drinking water, aflatoxins)
- The exposure is only relevant in specific parts of the world (mate, foods preserved by salting, Cantonese-style salted fish)
- There is inadequate information about certain factors (coffee, Mediterranean diet)
- The evidence is divergent between cancer sites (dairy products and calcium)
Issues of public health significance
The following exposures are judged to be causally linked to cancer risk but are not necessarily within the capacity of any individual to alter, and therefore inappropriate to include in the global Recommendations.
There is convincing evidence that developmental factors leading to greater growth in length in childhood (marked by adult attained height) are a cause of cancers of the colorectum, ovary and breast (both pre- and post menopause).
Developmental factors leading to greater growth in length in childhood (marked by adult attained height) are probably a cause of cancers of the pancreas, kidney, endometrium, prostate and skin (malignant melanoma).
Factors that lead to greater birthweight, or its consequences, are probably a cause of premenopausal breast cancer.
There is convincing evidence that consumption of arsenic in drinking water is a cause of lung cancer.
- Do not use any source of water that may be contaminated with arsenic.
- Authorities should ensure that safe water supplies are available when such contamination occurs.
There is convincing evidence that higher consumption of aflatoxin-contaminated foods is a convincing cause of liver cancer.
- Do not eat mouldy cereals (grains) or pulses (legumes).
- Governments should ensure that facilities for the safe storage of foods are made available in areas at risk of aflatoxin contamination.
Issues relevant only in specific parts of the world
Some evidence on the consumption of certain food and drink is specific to particular regions of the world.
Consumption of mate, as drunk in the traditional style in South America, is probably a cause of oesophageal squamous cell carcinoma.
- The Panel recognises that consumption of mate is a traditional practice in parts of South America. However, for cancer prevention, do not consume mate as drunk scalding hot in the traditional style.
Consumption of foods preserved by salting (including salt-preserved vegetables, fish and foods in general) is probably a cause of stomach cancer.
- Do not consume salt-preserved, salted, or salty foods.
- Preserve foods without using salt.
Consumption of Cantonese-style salted fish is probably a cause of nasopharyngeal cancer.
- Do not consume Cantonese-style salted fish.
- Children should not eat this type of fish.
Issues of inadequate information
For some exposures, although the Panel judged there to be strong evidence of an effect on cancer risk and the association was judged causal, some aspects of that evidence, such as the influence of dose, were inadequate to permit a meaningful recommendation.
Consumption of coffee probably protects against liver cancer and endometrial cancer. For liver cancer, no threshold was identified, and no evidence was found regarding specific components of coffee that might be responsible for the decreased risk.
For endometrial cancer, the effect was observed for both caffeinated and decaffeinated coffee and could not be attributed to caffeine.
Across the globe, coffee is consumed in different ways. Before a general recommendation on cancer prevention can be made, more research is needed to improve understanding of how the volume and regularity of consumption, type of coffee, and style of preparation and serving (many people add milk and sugar) affect the risk of cancer.
Many studies have included a measure of adherence to the so-called ‘Mediterranean type’ dietary pattern. However, although there are recognised scores for quantifying adherence to such a diet, it is unclear exactly what such a diet comprises. It generally describes a diet rich in fruit, vegetables and unrefined olive oil, with modest amounts of meat and dairy, and some fish and wine.
This diet is traditionally associated with high levels of physical activity. Such a diet is one of many ways of life that could be followed to meet the Recommendations.
Issues on which the evidence is divergent between cancer sites
For some exposures, where the Panel judged there to be strong evidence of an effect on risk of one or more cancers, there was evidence of an opposite effect on another cancer or other disease. In these circumstances, a general recommendation is inappropriate.
The evidence on dairy products and diets high in calcium is challenging to interpret.
Consumption of dairy products probably protects against colorectal cancer. Consumption of calcium supplements probably protects against colorectal cancer. There is strong evidence of a decreased risk for colorectal cancer.
There is also limited but suggestive evidence that consumption of dairy products might increase the risk of prostate cancer.
Even though the strength of the evidence for prostate cancer fell below the general threshold required for making a recommendation, the possibility of an adverse effect is sufficient to warrant caution. The evidence of potential for harm means the Panel chose to make no recommendation on dairy products.