SummaryThe relationship between estimated intake of selected micronutrients and the risk of colorectal cancer was analysed using data from a case-control study conducted in northern Italy. The There are indications that several micronutrients may influence the process of colorectal carcinogenesis. These include a potential protective effect of folate (Benito et al., 1991;Freudenheim et al., 1991), a co-factor in the methylation of thymidylate for DNA synthesis and the production of S-adenosylmethionine, the primary methyl donor in the body (Cooper, 1983); of calcium, which may react with fatty acids to form insoluble soaps (Newmark et al., 1984;Garland et al., 1985;Sorenson et al., 1988); and of ascorbic acid, Pcarotene and vitamin E, which may act as antioxidants (Iscovich et al., 1992;Longnecker et al., 1992). Two companion cohort studies (Giovannucci et al., 1993), including 564 women and 331 men with colorectal adenoma, have also suggested that folate may have a specific favourable effect on preneoplastic large bowel lesions. No convincing association for any micronutrients, however, has emerged from other studies (Peters et al., 1992), and the issue is therefore still unsettled, particularly since most studies did not make adequate allowance for various micronutrients.To provide further data on the issue, we have considered the role of selected micronutrients on colorectal carcinogenesis using data from a case-control study conducted in the greater Milan area, previously considered with reference to intake of specific foods (La Vecchia et al., 1988 The control group included patients admitted for a wide spectrum of acute, non-neoplastic, non-digestive tract conditions to the same network of hospitals where cases had been identified. Of these, 47% were admitted for traumatic conditions, 20% had non-traumatic orthopaedic diseases, 19% had acute surgical conditions, and 14% had other miscellaneous disorders. A total of 2,024 controls were included in the present analysis. The age range was 19-74 years, and the median age was 55 years. The catchment areas of cases and controls were comparable: over 80% of cases and controls resided in Lombardy, and over 90% came from northern Italy. Less than 3% of eligible subjects (cases and controls) refused to be interviewed.Trained interviewers used a structured questionnaire to obtain information on general sociodemographic factors and lifestyle habits, weight and height, a problem-oriented medical history and family history of colorectal cancer. Further, information on the frequency of consumption per week of 29 indicator foods was collected. These included major sources of P-carotene, retinol, ascorbic acid, vitamins D and E, folate, methionine and calcium in the Italian diet. We computed nutrient intake by multiplying the consumption frequency of each unit of food by the nutrient content of the standard average portions, using composition values from the Italian composition tables (Fidanza & Verdiglioni, 1988), with the integration of other sources when these were no...