Fatty Food, Prostate Cancer, and Death — A New Study Weighs In

Regularly eating certain dietary fats, including animal fats, was associated with greater all-cause mortality in men with nonmetastatic prostate cancer, a cohort study suggested.

Among nearly 4,900 men, the highest level of post-diagnosis saturated fat consumption was associated with greater all-cause mortality compared with the lowest level (HR 1.24, 95% CI 1.05-1.47), reported Lorelei Mucci, ScD, MPH, of the Harvard T.H. Chan School of Public Health in Boston, and colleagues.

As might be expected, death from cardiovascular disease was a likely reason for the increase in all-cause mortality (HR 1.42, 95% CI 1.02-1.98), they noted in JAMA Network Open.

In addition, animal fat, a major source of saturated fats, was positively associated with deaths from other cancers (HR 1.49, 95% CI 1.00-2.21). Notably, replacing 10% of calories from animal fats with plant-based fat sources (HR 0.84, 95% CI 0.76-0.93) and replacing 5% of calories from saturated fats with monounsaturated fats (HR 0.80, 95% CI 0.70-0.91) was associated with a decrease in all-cause mortality.

There was no association between consumption of dietary fats and prostate cancer mortality.

“This study coupled with prior epidemiologic studies provides evidence-based recommendations for patients and clinicians around dietary fat consumption to improve survivorship outcomes in the clinical setting of nonmetastatic prostate cancer,” Mucci and colleagues wrote.

In an accompanying commentary, David-Dan Nguyen, MDCM, MPH, of the University of Toronto, and colleagues noted that many patients with prostate cancer ask what they can do to improve their outcomes.

“This question is particularly relevant for men with nonmetastatic prostate cancer, many of whom will live for years or decades after diagnosis and face substantial competing risks from cardiovascular disease and other chronic conditions,” they wrote.

However, while clinicians want to offer practical guidance, survivorship guidelines — including those related to healthy lifestyle counseling — “are often supported by limited evidence and remain inconsistently implemented,” Nguyen and team pointed out.

“Clinicians should not present dietary fat modification as a proven prostate cancer-directed therapy, but neither should they ignore an important opportunity to promote health when patients are motivated to act,” they noted.

“For patients, the message can be framed simply: a healthier diet may not treat prostate cancer directly, but it remains an important means of caring for the whole person living with prostate cancer,” they added. “Among individuals with nonmetastatic prostate cancer, cardiovascular disease is a leading and often more common cause of death than prostate cancer itself. Therefore, using the period after diagnosis to improve diet, physical activity, smoking status, and cardiometabolic risk may provide substantial benefits, even without a demonstrated effect on prostate cancer-specific mortality.”

Mucci and colleagues included 4,884 participants in the Health Professionals Follow-Up Study — a cohort of more than 50,000 male health professionals from across 50 states ongoing since 1986 — with confirmed nonmetastatic prostate cancer between 1986 and January 2019. They were followed through December 2022.

Mean age at diagnosis was 69.5, 97% were white, 62% received a diagnosis of clinical stage T1 disease, and 10% had tumors with a Gleason score of 8 to 10.

Median follow-up was 12.8 years, “which is key given the long-term natural history of outcomes in nonmetastatic prostate cancer,” the authors noted.

Data on diet were collected using validated semiquantitative food frequency questionnaires every 4 years.

Participants with higher saturated, trans, and animal fat intakes were more likely to be current smokers and have a higher body mass index, lower physical activity levels, and diabetes. During follow-up, 3,040 patients died from any cause, which included 441 due to prostate cancer, 499 due to other cancers, and 803 due to cardiovascular disease.

Mucci and colleagues acknowledged that their study had limitations, including their inability to examine specific fatty acids.

“Given that certain fatty acids may be more beneficial or harmful, classifying them together in groups may lead to conflicting results between studies depending on the different components of diets,” they wrote.