The World Cancer Research Fund has published a blog reiterating its conviction that "fruits and vegetables probably do reduce risk of cancer, although the evidence is not strong enough for us to be certain."It says any direct protective effect seems to be limited to certain types of cancer such as those of the stomach, oesophagus, mouth, pharynx and larynx – and because fruits and vegetables are only linked to the risk of certain types of cancer, the percentage of overall cancer cases that could be prevented is quite small.

However, the blog continues: "because there are so many cases of cancer diagnosed every year, this still means thousands of cases could be prevented each year if everyone ate more fruits and vegetables". A paper in the British Journal of Cancer describes a literature review of the best studies to date investigating whether eating more fruit and vegetables reduces the risk of getting cancer. The author, Professor Tim Key of Oxford University, writes that the research suggests there is little or no benefit for relatively well-nourished, westernised populations. Even where studies have found a moderate reduction in risk, this may be accounted for by "confounding factors", namely alcohol consumption and smoking. In other words, the results are confused because people with poor diets tend to smoke and drink more than those with good diets.

The studies looked at overall fruit and veg consumption, and Key concedes that particular nutrients in certain fruits and vegetables may reduce the risk of specific cancers.