UTHSC Key Site in National Study Showing Link Between Low Fat Diet and Women’s Risk of Death from Breast Cancer

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Dr. Karen C. Johnson (Photo by Allen Gillespie/UTHSC)

Researchers at the University of Tennessee Health Science Center (UTHSC) were part of the federally-funded Women’s Health Initiative (WHI) multisite clinical trial, which released study findings last week showing that postmenopausal women with no previous history of breast cancer reportedly had a 21 percent lower risk of death from breast cancer if they followed a low-fat, balanced diet compared to those who had a diet higher in fat.

Obesity rates have drastically increased over the past several decades. If current trends continue over the next 20 years, it is estimated that obesity will lead to more than 500,000 additional cases of cancer each year in the United States. More disturbingly, studies show that the majority of Americans remain unaware that obesity is a risk factor for cancer including breast cancer.

To combat these frightening statistics, the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) launched the WHI low-fat dietary modification clinical trial in 1993. Nearly 49,000 postmenopausal women ages 50 to 79 with no previous history of breast cancer were enrolled across 40 clinical trials sites in the U.S. The women were randomly assigned to their normal diet where fat accounted for at least 32 percent or more of their daily caloric intake, or to a diet with a 20 percent or less reduced fat consumption goal plus a higher number of servings of vegetables, fruits, and grains incorporated into their daily diets. Women in the balanced, low-fat diet group followed the program for approximately 8.5 years. All the participants were tracked after intervention completion to see if they died from any cause or from breast cancer.

Memphis hosts two WHI study sites, following over 4,200 participants. The UTHSC site was overseen by Karen C. Johnson, MD, MPH, principal investigator, College of Medicine Endowed Professor in Women’s Health, and professor of Preventive Medicine at UTHSC.

“The WHI Diet Modification trial has given us important new information for women – you can reduce your risk of dying from breast by eating a healthy diet that is high in fruit and vegetables and low in fat,” said Dr. Johnson. “This type of diet can also help control weight gain as women age.”

The trial has followed participants for nearly 20 years, and of the roughly 49,000 participants, only 3,374 cases of breast cancer were diagnosed in the low-fat diet intervention group between 1993 and 2013. Moreover, women in the intervention group experienced a 15 percent lower risk of death from any cause after a breast cancer diagnosis and a 21 percent lower risk of death solely from breast cancer when compared to women who followed their normal diet.

“This study shows that diet can make a difference in the risk of dying from breast cancer,” said Monica M. Bertagnolli, MD, FACS, FASCO, president of the American Society of Clinical Oncology. “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.”

The researchers have also conducted a similar study examining the same dietary modifications in women with poor metabolic function, such as diabetes and high blood pressure, which effects roughly five million American women today. Preliminary results show that a balanced, low-fat diet could lead to a major reduction in breast cancer deaths in the U.S. and large reduction in health care costs, as disease prevention is not only better for overall health but is also significantly less expensive than treating cancer once developed.

Researchers will continue to periodically monitor the women’s health. The WHI study results will be presented at the 2019 American Society of Clinical Oncology Annual Meeting in Chicago.