The DIANA-5 trial randomly assigned 1,542 women aged 35 to 70 who had been treated for breast cancer within the last 5 years to one of two groups. 

The active group got kitchen classes, community meals, and diet advice (to eat whole grains, beans, soy foods, vegetables, fruits, nuts, olive oil, and fish and to avoid refined grains, potatoes, sugar, red or processed meats, butter, cheese, and alcohol). The control group got just diet advice.

All the women had a high risk of recurrence because they had estrogen receptor-negative cancer, high blood insulin or testosterone, or the metabolic syndrome.

After 5 years, there was no difference in recurrence between groups.

What to do

This study didn’t prove that a healthy diet prevents recurring breast cancer. That said, a healthy diet can protect your heart... so why not?