470 Am J C/in Nuir 1990;52:470-6. Printed in USA. © 1990 American Society for Clinical Nutrition Quantitative changes in dietary fat intake and serum cholesterol in women: results from a randomized, controlled trial1’2 Norman F Boyd, Mary Cousins, Mary Beaton, Valentina Kriukov, Gina Lockwood, and David Tritchler ABSTRACT We compared observed and predicted changes in serum cholesterol in women with mammographic dysplasia who participated for 12 mo in a randomized, con- trolled trial ofa low-fat, high-carbohydrate diet, in which total fat intake was reduced from an average of 37% of calories to 2 1% and carbohydrate intake increased from 44% to 52% of calories. Changes observed in serum cholesterol were greater than those predicted (by the formulas ofHegsted and Keys) for subjects with initial serum cholesterol values in the upper ter- tile of the population, were not significantly different from those predicted for subjects with baseline values in the middle tertile, and were significantly less than those predicted for sub- jects with initial values in the lower tertile. These results show that the usefulness of serum cholesterol as a marker of change in dietary fat intake in women depends on the distribution of serum cholesterol values in the population studied. Am J C/in Nutr 1990;52:470-6. KEY WORDS Dietary fat, serum cholesterol, randomized trial, women Introduction Evidence from animal experiments clearly shows that risk of breast cancer can be modified by nutrition variables, including the total intake ofcalories and the fat content ofthe diet (1-5). Increased dietary fat intake increases the number of animals that develop mammary tumors, the number ofboth malignant and benign tumors, and the proliferative activity of the mam- mary epithelium. The relevance of these findings to breast-cancer risk in hu- mans is presently unclear because of conflicting evidence (6- 1 8) but could in principle be examined in the experimental set- ting ofa clinical trial ofdietary fat reduction. Subjects could be randomly assigned to experimental and control groups, sub- jects in the experimental group could be taught to reduce their intake of dietary fat, and subjects in both groups could be ob- served for possible effects of dietary fat reduction on breast- cancer risk. A major source ofdifficulty in conducting such a trial, how- ever, is the assessment ofdietary fat intake, which requires the use of food records, and the absence of biological markers to monitor such reports. To be useful in this context, a biological marker should change quantitatively in a predictable way in response to a change in nutrient intake. This would be most useful ifchanges in the marker corresponded to changes in the nutrient intake of individuals, but failing that, a marker that corresponded to changes in the nutrient intake ofgroups would be valuable in clinical trials ofdietary fat reduction. We carried out a randomized, controlled trial of dietary fat reduction in patients with mammographic dysplasia, a group found in previous work to be at increased risk of breast cancer ( 19). The initial goals of this study were to determine if it is feasible to carry out a trial ofdietary fat reduction in this group of patients, to assess compliance with a reduced-fat diet, and to assess the effect of a reduction in dietary fat intake on the radiobogic appearance ofmammographic dysplasia after 1 y on the new diet. Details of feasibility, dietary compliance, and ra- diologic outcomes were described elsewhere (20). We report here the quantitative relationship found in this trial between changes in nutrient intake and the changes ob- served in serum cholesterol. The principal method of assessing compliance in the trial was the nutrient analysis of food rec- ords. In addition, serum cholesterol was measured in all pa- tients at randomization and at intervals afterwards, corre- sponding to when food records were collected. Subjects and methods Selection and recruitment of subjects Subjects were eligible for the trial if they were aged 30 y and had been examined by mammography within 3 mo of en- try and found to have 50% ofthe breast volume occupied by the radiologic changes of dysplasia. Subjects were excluded if they were pregnant or breast-feeding, ifthey were taking a med- ically prescribed diet, or ifthey had a previous history of breast cancer. Ethical approval for the trial was obtained from the University of Toronto. Of 295 women who entered the trial, 239 completed 12 From the Ludwig Institute for Cancer Research, Toronto Branch, and Ontario Cancer Institute, Toronto. 2 Address reprint requests to NF Boyd, Princess Margaret Hospital, 500 Sherbourne Street, Toronto, Ontario, Canada M4X I K9. Received March 21, 1989. Accepted for publication October 25. 1989. by guest on July 10, 2011 www.ajcn.org Downloaded from