Fruit and vegetables, and human cancer

A large body of evidence indicates that high intakes of fruit and vegetables are associated with a reduced risk of cancer at several sites. The association is generally most marked for epithelial cancers, apparently stronger for those of the digestive and respiratory tracts, and somewhat weaker for hormone-related cancers. The relationship between frequency of consumption of vegetables and fruit and cancer risk was analysed using data from a series of case-control studies conducted in northern Italy since 1983. The relative risks (RRs) for most common neoplasms ranged from 0.2 to 0.5 for the highest compared with the lowest tertile of vegetable intake. Protective effects were highest for epithelial neoplasms, but were also observed for hormone-related neoplasms. Fruit was related to reduced RRs for cancers of the oral cavity and pharynx, oesophagus, stomach, larynx, as well as of the urinary tract. There was a specific and consistent pattern of protection by tomatoes, a typical Mediterranean food, with RRs between 0.4 and 0.7, most notably for gastrointestinal neoplasms. No significant association was observed between fruit and vegetable consumption and non-epithelial lymphoid neoplasms. For digestive tract cancer, population attributable risks for low intake of fresh vegetables and fruit ranged from 15 to 40% of all cases in this Mediterranean population. Combined with tobacco and alcohol, the population attributable risks exceeded 85% for men and 55% for women for upper digestive and respiratory tract neoplasms. Thus, from a public health viewpoint, epidemiological evidence indicates that a substantial reduction in epithelial cancer risk can be obtained by increasing fruit and vegetable consumption.