Diet and cancer

South African Journal of Obstetrics and Gynaecology, April, 2008

A major report has just been published by the World Cancer Research Fund on the links between diet and cancer. The contributors are international experts and the work took 5 years, so its conclusions can be taken seriously. They make four points we should note.

* Obesity increases the risk of cancer of the oesophagus, colorectum, pancreas, breast, endometrium and kidney. The ideal body mass index is between 21 and 23, but the mean BMI in the UK is 27 at present (Key, BMJ 2007; 335: 897).

* Alcohol increases the risk for cancer of the mouth, pharynx, larynx, oesophagus, colorectum and breast--in addition to which it cases cirrhosis which predisposes to liver cancer. They recommend a maximum of 2 units a day for men and 1 for women, although the current 'standard drink or tot' is inconsistent. The British measure of a beer or glass of wine contains 8 g ethanol, whereas other countries' 'single drink' contains 10-15 g alcohol (Seabrook, p. 1008).

* Fruit and vegetables protect against cancers and the recommendation remains 5 portions per day, but the experts admit that the mechanism of action is not clear. The role of fibre as the means of protection is not compelling.

* They come out strongly against red and processed meat, declaring that they 'convincingly cause colorectal cancer'. This is a much more resolute stance than in previous reports, saying that those people eating the most red and processed meat have a 30% increased risk compared with those eating the least. They recommend 300 g per week, whereas the average in Western countries is 3 times that at present.