By Megan Brooks

A balanced, low-fat diet significantly lowers the risk of dying from breast cancer in postmenopausal women, according to new long-term data from the Women’s Health Initiative (WHI) Dietary Modification trial.

“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,” lead investigator Dr. Rowan Chlebowski from Harbor-UCLA Medical Center in Torrance, California, said in a statement.

He discussed the findings during a press briefing May 15 ahead of a presentation June 2 at the American Society of Clinical Oncology (ASCO) annual meeting.

“This study makes clear there are no down-sides, only up-sides to a healthier diet, and it adds to a growing volume of studies showing similar positive effects across cancer types,” ASCO President and briefing moderator Dr. Monica M. Bertagnolli said in the statement.

The trial enrolled 48,835 postmenopausal women with no previous breast cancer and with dietary fat accounting for at least 32 percent of total daily calories. From 1993 to 1998, the women were randomly allocated to a usual-diet comparison group or a dietary intervention group that aimed to reduce fat intake to 20 percent of daily calories and increase consumption of vegetables, fruit and grains.

Women in the balanced, low-fat diet group stuck to the diet for roughly 8.5 years. Most of them increased their intake of fruits, vegetables and grains and cut their daily fat intake to 25 percent or less, although most did not reach the 20 percent goal.

The research team was able to track half of the women for more than 19.6 years.

A total of 3,374 women developed breast cancer between 1993 and 2013. The low-fat diet did not significantly reduce women’s risk of developing breast cancer – still, women in the dietary intervention group experienced a range of short- and long-term health benefits as compared with women in the normal diet group, Chlebowski noted. Specifically, they had a 21 percent lower risk of death from breast cancer and a 15 percent lower risk of death from any cause during the follow up period.

Postmenopausal women with metabolic syndrome (increased blood pressure, high blood sugar, excess body fat around the waist and abnormal cholesterol or triglyceride levels) were particularly likely to benefit from the dietary intervention.

Commenting on the findings during the briefing, Dr. Lidia Schapira from Stanford Cancer Institute in California said this study is “very important and helps us understand that what we put on the plate matters and it is worth coaching and pushing our patients to put fruits, vegetables and grains on their plate.”

She continued, “This is not easy, Dr. Chlebowski said that they did not accomplish reducing the dietary fat as much as they had intended to, but even at the level that they did, they showed that there was a health advantage.”

“Quality of the diet and dietary patterns over time are an important component of long-term health in women with breast cancer,” Kelly Hogan, a registered dietician and clinical nutrition and wellness manager at Mount Sinai’s Dubin Breast Center of the Tisch Cancer Institute in New York City, told Reuters Health by email.

“The health benefits of a plant-based diet are well known, and this study further emphasizes the importance and possible protective factors of a diet high in plant foods, such as fruits, vegetables and whole grains, in women with breast cancer, as well as the importance of continued nutritional guidance from their healthcare teams to help them adapt these dietary changes throughout their treatment and beyond,” said Hogan, who was not involved in the study.

SOURCE: American Society of Clinical Oncology Annual Meeting, May 15, 2019.