EFFECTS AT 2 YEARS OF A LOW-FAT, HIGH-CARBOHYDRATE DIET ON RADIOLOGICFEATURES OF THE BREAST - RESULTS FROM A RANDOMIZED TRIAL

Background: The appearance of breast tissue on mammography varies acco rding to its composition, Fat is radiolucent and appears dark on mammo graphy, while stromal and epithelial tissue has greater optical densit y and appears light, Extensive areas of radiologically dense breast ti ssue seen on mammography are associated with an increased risk of brea st cancer, Purpose: The purpose of the present study was to determine whether the adoption of a low-fat, high-carbohydrate diet for 2 years would reduce breast density. Methods: Women with radiologic densities in more than 50% of the breast area on mammography were recruited and randomly allocated to an intervention group taught to reduce intake of dietary fat (mean, 21% of calories) and increase complex carbohydrate (mean, 61% of calories) or to a control group (mean, 32% of calories from fat and 50% of calories from carbohydrates), Mammographic images from 817 subjects were taken at baseline and compared with those taken 2 years after random allocation by use of a quantitative image analys is system, without knowledge of the dietary group of the subjects or o f the sequence in which pairs of images had been taken, The effects of the intervention on the mammographic features of breast area, area of dense tissues in the breast, and the percent of the breast occupied b y dense tissue were examined using t tests, Multiple regression was us ed to examine these effects while accounting for age at trial entry, w eight change, and menopausal status, Results: After 2 years, the total area of the breast was reduced by an average of 233.7 mm(2) (2.4%) (9 5% confidence interval [CI] = 106.9-360.6) in the intervention group c ompared with an average increase of 26.3 mm(2) (0.3%) (95% CI = -108.0 -160.5) in the control group (P = .01), The area of density was reduce d by 374.4 mm(2) (6.1%) (95% CI = 235.1-513.8) in the intervention gro up compared with an average of 127.7 mm(2) (2.1%) (95% CI = 8.6-246.7) in the control group (P = .01), Weight loss was associated with a red uction in breast area, The effect of the intervention on breast area w as only marginally statistically significant after weight change, meno pausal status, and age at trial entry were taken into account (P = .06 ). Greater weight loss and becoming postmenopausal were associated wit h statistically significant reductions in the area of density on the m ammographic image at 2 years (P = .04 and P < .001, respectively), Age at entry into the trial was marginally significant in the same direct ion (P = .06). The effect of the intervention on area of density remai ned statistically significant after controlling for weight loss, age a t entry, and menopausal status (P = .03), The change in the percentage of dense tissue in the mammographic image was not significantly diffe rent between the two groups (P = .71), Conclusions and Implications: T hese results show that after 2 years, a low-fat, high-carbohydrate die t reduced the area of mammographic density, a radiographic feature of the breast that is a risk factor for breast cancer, Longer observation of a larger number of subjects will be required to determine whether these effects are associated with changes in risk of breast cancer.