These results demonstrate that serum lipids are associated with breast cancer risk in women with extensive mammographic density. The possibility that interventions for heart disease prevention, which aim to reduce non-HDL-C or raise HDL-C, may have effects on breast cancer risk merits examination.

Overall, the LFHC dietary intervention did not influence the timing of menopause. Factors associated with age at menopause in this population were consistent with those reported in other populations.

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.