Long-Term Healthy Diet Reduces Breast Cancer Mortality in Postmenopausal Women

Research to be presented at the upcoming 2019 American Society of Clinical Oncology Annual Meeting found that a balanced, low-fat diet significantly lowers the risk of breast cancer mortality in postmenopausal women.

The randomized, controlled Women’s Health Initiative Dietary Modification clinical trial was conducted at 40 U.S. centers and included 48,835 postmenopausal women who were 50 to 79 years. Participants did not previously have breast cancer, and they had a dietary fat intake of ≥32% of total daily calories.

Between 1993 and 1998, women were randomized to a usual diet comparison group (60%) or dietary intervention group (40%) that aimed to reduce fat intake to 20% of daily calories and increase the intake of vegetables, fruits, and grains.

Healthy diet group has lower mortality

The dietary intervention significantly reduced fat intake and increased fruit, vegetable, and grain intake (P<0.001). This cohort also experienced modest weight loss (3%; P<0.001). During 8.5 years of the dietary intervention, there were 8% fewer breast cancers. Deaths from breast cancer were somewhat lower in the intervention group; however, this was not statistically significant.

Deaths after breast cancer (breast cancer followed by death from any cause) were significantly reduced in the intervention group, both during the intervention (hazard ratio [HR] = 0.65; 95% CI, 0.45-0.95) and through a median of 16.1 years of follow-up.

After a median follow-up of 19.6 years, there were 3,374 incident breast cancers. In the intervention group, there was a statistically significant 21% lower risk for death from breast cancer (breast cancer followed by death attributed to the breast cancer) compared with the control group (HR=0.79; 95% CI, 0.64-0.97). There was also a significant 15% reduction in deaths from all causes after a breast cancer diagnosis in the intervention group (HR=0.85; 95% CI, 0.74-0.96).

“Ours is the first randomized, controlled trial to prove that a healthy diet can reduce the risk of death from breast cancer. The balanced diet we designed is one of moderation, and after nearly 20 years of follow-up, the health benefits are still accruing,” said lead investigator Rowan Chlebowski, MD, PhD, from Harbor-UCLA Medical Center in Torrance, California, in a statement.