OLIVE OIL, OTHER SEASONING FATS, AND THE RISK OF COLORECTAL-CARCINOMA

BACKGROUND. An association between fats and colorectal carcinoma has b een suggested, but the epidemiologic evidence by type of dietary fat i s far less clear. Colorectal carcinoma rates have been relatively low in Mediterranean countries compared with most other Western countries, but the components of the Mediterranean diet responsible for this fav orable pattern are unclear. METHODS. The relationship between various added (seasoning) fats and colorectal carcinoma risk was investigated using data from a case-control study conducted between January 1992 an d June 1996 in six Italian areas. Cases were 1953 patients with incide nt, histologically confirmed colorectal carcinoma (1225 of the colon a nd 728 of the rectum) admitted to the major teaching and general hospi tals in the study areas, Controls were 4154 subjects with no history o f cancer who were admitted to hospitals in the same catchment areas fo r acute, nonneoplastic diseases unrelated to the the digestive tract a nd requiring no long term modifications of diet. Dietary habits were i nvestigated using a validated food frequency questionnaire including 7 8 items. Lipid intake was estimated by laking into account the content of seasoning lipids in different dishes, the frequency of consumption and portion size of each dish, and individual fat intake patterns. RE SULTS. The odds ratios (OR) for successive tertiles of olive oil intak e, compared with the lowest one, were 0.87 (95% confidence interval [C I], 0.75-1.01) and 0.83 (95% CI, 0.10-0.99) (chi(trend)(2) = 4.49, P = 0.03) when colorectal carcinoma was analyzed as a whole, 0.82 (95% CI , 0.68-0.98) and 0.81 (95% CI, 0.66-0.99) (chi(trend)(2) = 4.05, P = 0 .04) for colon carcinoma, and 0.96 (95% CI, 0.77-1.19) and 0.88 (95% C I, 0.66-1.12) for rectal carcinoma. For specific seed oils (including sunflower, maize, peanut, and soya), the OR for colorectal carcinoma w as 0.91 in the highest tertile of intake, and the corresponding values were 1.01 for mixed seed oils and 0.93 for butler. None of these esti mates was significantly different from the unity. Allowance for vegeta ble intake attenuated the apparent protection from olive oil consumpti on (OR, 0.94 for colon and 0.97 for rectum for the highest tertile), w hich still was apparent in younger subjects (OR, 0.82 for colon and 0. 69 for rectum). CONCLUSIONS. In this study, seasoning fats did not app ear to increase the risk of colorectal carcinoma, and there was little evidence for a differential effect by fat type. If such a differentia l effect exists, it is minor and could favor olive oil. (C) 1998 Ameri can Cancer Society.