A case-control study of diet and gastric cancer in northern Italy.

Dietary factors in the aetiology of stomach cancer were investigated using data from a case-control study conducted in Northern Italy on 206 histologically confirmed carcinomas and 474 control subjects in hospital for acute, non-digestive conditions, unrelated to any of the potential risk factors for gastric cancer. Dietary histories concerned the frequency of consumption per week of 29 selected food items (including the major sources of starches, proteins, fats, fibres, vitamins A and C, nitrates and nitrites in the Italian diet) and subjective scores for condiments and salt intake. Pasta and rice (the major sources of starch), polenta (a porridge made of maize) and ham were positively related with gastric cancer risk, whereas green vegetables and fresh fruit as a whole (and specifically citrus fruit) and selected fibre-rich aliments (such as whole-grain bread or pasta) showed protective effects on gastric cancer risk. Allowance for major identified potential distorting factors (chiefly indicators of socio-economic status) reduced the positive association with pasta or rice consumption, but did not appreciably modify any of the other risk estimates. When a single logistic model was fitted including all food items significant in univariate analysis, the 3 items remaining statistically significant were green vegetables (relative risk, RR = 0.27 for upper vs. lower tertile), polenta (RR = 2.32) and ham (RR = 1.60). Indices of beta-carotene and ascorbate intake were negatively and strongly related with gastric cancer risk, but the association with these micronutrients was no longer evident after simultaneous allowance for various food items. An approximately 7-fold difference in risk was found between extreme quintiles of a scale measuring major positive and negative associations.