Vegetable fat may be associated with lower risk of death in men with nonmetastatic prostate cancer

Replacing carbohydrates and animal fat with vegetable fat may be associated with a lower risk of death in men with nonmetastatic prostate cancer, according to a report published Online First by JAMA Internal Medicine, a JAMA Network publication.

"Nearly 2.5 million men currently live with prostate cancer in the United States, yet little is known about the association between diet after diagnosis and prostate cancer progression and overall mortality," according to the study background.

Erin L. Richman, Sc.D., of the University of California, San Francisco, and colleagues at UCSF examined fat intake after a diagnosis of prostate cancer in relation to lethal prostate cancer and all-cause mortality. The study included 4,577 men diagnosed with nonmetastatic prostate cancer between 1986 and 2010 who were enrolled in the Health Professionals Follow-up Study.

Researchers noted 315 lethal prostate cancer events and 1,064 deaths during a median (midpoint) follow-up of 8.4 years. Replacing 10 percent of calories from carbohydrates with vegetable fat was associated with a 29 percent lower risk of lethal prostate cancer and a 26 percent lower risk of death from all-cause mortality, according to the study results.

"In this prospective analysis, vegetable fat intake after diagnosis was associated with a lower risk of lethal prostate cancer and all-cause mortality," the authors comment. The authors note oils and nuts were among the top sources of vegetable fats in the study population.

Crude rates of lethal prostate cancer (per 1,000 person-years) comparing the highest and lowest quintiles of fat intake were: 7.6 vs. 7.3 for saturated; 6.4 vs. 7.2 for monounsaturated; 5.8 vs. 8.2 for polyunsaturated; 8.7 vs. 6.1 for trans; 8.3 vs. 5.7 for animal; and 4.7 vs. 8.7 for vegetable fat. For all-cause mortality, crude death rates (per 1,000 person-years) comparing the highest and lowest quintiles of fat intake were: 28.4 vs. 21.4 for saturated; 20.0 vs. 23.7 for monounsaturated; 17.1 vs. 29.4 for polyunsaturated; 32.4 vs. 17.1 for trans; 32.0 vs. 17.2 for animal; and 15.4 vs. 32.7 for vegetable fat, according to the study results.

"Overall, our findings support counseling men with prostate cancer to follow a heart-healthy diet in which carbohydrate calories are replaced with unsaturated oils and nuts to reduce the risk of all-cause mortality. … The potential benefit of vegetable fat consumption for prostate cancer-specific outcomes merits further research," the authors conclude.
(JAMA Intern Med. Published online June 10, 2013. doi:10.1001/jamainternmed.2013.6536. Available pre-embargo to the media at http://media.jamanetwork.com.)

Editor's Note: This work was supported by grants from the National Institutes of Health, the Department of Defense and the Prostate Cancer Foundation. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Commentary: Dietary Fat, Reduced Prostate Cancer Mortality

In an invited commentary, Stephen J. Freedland, M.D., of the Duke University Medical Center, Durham, N.C., writes: "Using data from food frequency questionnaires completed every four years during follow-up, they found that men who consumed more vegetable fat had a lower risk of prostate cancer death."

"Thus, in the absence of randomized trial data, it is impossible to use these data as 'proof' that vegetable intake lowers prostate cancer risk, and the authors have carefully avoided such statements," Freedland continues.

"When counseling patients, I remind them that obesity is the only known modifiable risk factor linked with prostate cancer mortality to date. Thus, avoiding obesity is essential. Exactly how this should be done remains unclear, although the data by Richman et al suggest that substituting healthy foods (i.e. vegetable fats) for unhealthy foods (i.e. carbohydrates) may have a benefit. Determining whether this benefit is due to reduced consumption of carbohydrates or greater intake of vegetables will require future prospective randomized trials," Freedland concludes.

Study: University of California