CHANGES IN DIETARY-FAT INTAKE PRECEDING THE DIAGNOSIS OF CANCER

We studied changes in dietary fat intake preceding the diagnosis of ca ncer in 96 men diagnosed with cancer during the Coronary Primary Preve ntion Trial and Post-trial Follow-up. Diet was assessed semiannually b y 24-hour recall for the duration of the trial. Dietary fat intake was elevated in the interval 12-24 months before diagnosis compared with the interval 24-36 months before diagnosis [6.9 gm per day; 95% confid ence interval (CI) = 0.04-13.7]. The percentage of calories as fat was also elevated (1.9%; 95% CI = 0.34-3.4). Fat consumption decreased in the 0- to 12-month prediagnostic interval. The basis for the elevatio n is unclear, but it may have been due to the metabolic effects of can cer before its diagnosis. Case-control studies of long term diet may o verestimate positive associations between dietary fat and cancer risk if the cases' recall includes the prediagnostic period, during which f at intake is elevated. In analyses of prospective studies of dietary f at and cancer, data from within the first 2-3 years of baseline should be examined separately to evaluate the potential for bias introduced by the inclusion of measurements representing transient elevations in dietary fat intake.