David I Conway of the University of Glasgow Dental School has published a paper in the journal Evidence-Based Dentistry, which claims that each portion of fruit and vegetable consumed halves the risk of oral cancer.

Some 16 observational studies from worldwide literature and provided diet data from nearly 5,000 individuals was used in the study and the main findings were that each portion of fruit and vegetable consumed per day reduced the risk of oral cancer by around 50 per cent.

Rising incidence of oral cancer across the UK is not entirely explained by trends in the traditional risk factors, namely tobacco smoking and alcohol consumption. The paper - Association between fruit and vegetable consumption and oral cancer: a meta-analysis of observational studies, is built on work begun by the World Cancer Research Fund’s ground-breaking systematic review, which found “convincing” evidence that diets high in fruit and vegetables decrease the risk of cancers of the mouth and pharynx.

A total of 71 potentially relevant studies were identified: 16 were included in the meta-analysis. Seven studies had been carried out in Europe, five in the Americas and four in East Asia. Three case-control studies consisted solely of men and one study consisted solely of women. The combined adjusted odds ratio (OR) estimates based on 16 studies showed that each portion of fruit consumed per day had a statistically significant effect, reducing the risk of oral cancer by 49 per cent. A similar effect was seen for vegetable consumption, with a significant reduction in the risk of oral cancer of 50 per cent. Homogeneity testing found a statistically significant heterogeneity for fruit consumption and vegetable consumption studies. This was examined using sensitivity analysis, which did not substantially modify the main findings of the meta-analysis.

The practice point of the study concluded that the consumption of five portions of fresh fruit and vegetables a day is a key health message that has relevance to oral as well as general health.