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Want to reduce your risk of dying from breast cancer? Start eating a low-fat, plant-based diet before the disease develops. That’s the advice from a long-term analysis of the federally funded Women’s Health Initiative.

The study followed nearly 49,000 postmenopausal women for twenty years. The participants had no previous history of breast cancer and their fat intake accounted for 32% or more of their daily calories. For one group, their goal was to limit their daily calories from fat to 20% and to eat at least one serving of vegetables, fruits, and grains daily. The rest continued their usual eating habits.

The low-fat diet group missed the target but did cut their fat intake to 24% after one year. The group followed the diet for about eight and a half years. Fat intake in the comparison group stayed about the same.

Researchers from the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center analyzed the data and found those who stuck to the low-fat, plant-based diet had a 20% lower risk of dying from breast cancer. However, the study did not find a significant drop in breast cancer diagnoses.  The results also showed that the low-fat diet group had a 15% lower risk of death from any cause after a breast cancer diagnosis.

Diane Riccardi, a clinical dietician at Moffitt Cancer Center, says multiple factors contribute to the development and growth of cancer. She says the overall result is exciting news for breast cancer survivors, as it is the first randomized clinical trial to show that dietary change, even small changes, can improve outcomes.

“Women in this study achieved a healthier diet by making substitutions in what they normally ate, choosing smaller portions and using different cooking methods, not by completely changing their usual diet,” Riccardi explained. “These study results reinforce our practice of providing nutrition counseling and health promotion as part of the treatment plan for all cancer survivors.”

The researchers caution that it’s too soon to say that a low-fat, plant-based diet does not protect women from getting breast cancer and more studies are needed.

This study is being presented at the American Society of Clinical Oncology Annual Meeting later this month.