Fruits and vegetables: updating the epidemiologic evidence for the WCRF/AICR lifestyle recommendations for cancer prevention.

The World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) current dietary recommendations for cancer prevention include "eating at least five portions/servings of a variety of non-starchy vegetables and or fruits every day". The most recent report coordinated by WCRF/AICR (2007) concluded that the evidence of a protective effect of fruits and vegetables on cancer was either "probable"-mouth, pharynx and larynx, oesophagus stomach, lung- or "limited suggestive"-nasopharynx, lung, colorectum, ovary, endometrium, pancreas, liver-. In a previous report published by WCRF/AICR in 1997, the evidence of the association of fruits and vegetables with cancer risk was considered convincing. This judgement was based mainly on the results of case-control studies. The association of fruit and vegetable intake and the risk of colorectal, breast and pancreatic cancer was re-examined in the Continuous Update Project (CUP) and the results were quantitatively summarised in meta-analyses. The CUP, with more data available, has confirmed the conclusion of the WCRF/AICR second expert report that there is no convincing evidence that fruits and vegetables play a role on cancer aetiology. On the other hand, evidence that is more consistent has been collected in the CUP about the role of dietary fibre and colorectal cancer. The evidence on the role of dietary fibre in colorectal cancer aetiology has been recently upgraded by the CUP expert panel from probable to convincing.