Effect of a low-fat, high-carbohydrate dietary intervention on change in mammographic density over menopause

We have previously shown that a low-fat dietary intervention for 2 years in women with extensive mammographic density decreased mammographic density to a greater extent than in the control group. Post-hoc analysis indicated that this effect was strongest in women who became postmenopausal during the follow-up period. The purpose of the present study was to determine if this potentially important finding could be confirmed in a new and larger group of subjects with a longer follow-up time. Participants in a low-fat dietary intervention trial who were premenopausal at entry and became postmenopausal during follow-up were examined. Total breast, dense, and non-dense area and percent density were measured in baseline and postmenopause mammograms using a computer-assisted method. Total breast and non dense area increased more in the control group compared to the intervention group (for breast area 2.6 and 0.2 cm(2), respectively; P=0.05, and for non-dense area 10.9 and 8.1 cm(2), respectively; P=0.06). Dense area decreased to a similar degree in both groups (-8.2 and -8.0 cm(2), respectively; P=0.84). Percent density decreased to a slightly greater degree in the control compared to intervention group (-9.4 and -7.8%, respectively, P=0.11). There were no significant differences between study groups after adjustment for weight change. Menopause reduced density to a similar extent in the low-fat diet and control groups. If a low-fat diet reduces breast cancer risk, the effect is unlikely to be through changes in mammographic density at menopause.