Higher saturated fat intake associated with increased mortality in nonmetastatic prostate cancer

Postdiagnostic intake of saturated and animal fats was associated with higher all-cause mortality among men with nonmetastatic prostate cancer, whereas replacing those fats with plant-based or monounsaturated fats was associated with lower mortality, according to findings from a prospective cohort study published in JAMA Network Open.¹

The analysis of 4884 men from the Health Professionals Follow-Up Study found that participants in the highest quintile of saturated fat consumption after prostate cancer diagnosis had a 24% higher risk of all-cause mortality than those in the lowest quintile (HR, 1.24; 95% CI, 1.05 to 1.47). The association was primarily attributable to cardiovascular disease and other cancers.

“These findings suggest that diet after diagnosis may be one modifiable component of survivorship care, broadening the focus beyond control of the original tumor,” said co-senior author Lorelei A. Mucci, ScD, MPH, professor of epidemiology at Harvard Chan School, in a news release on the findings.² “Protecting cardiovascular and overall health is an essential part of prostate cancer care, particularly because some treatments can affect metabolic and cardiovascular health.”

Study design and findings

Investigators analyzed data from the Health Professionals Follow-Up Study, an ongoing prospective cohort that enrolled 51,529 male health professionals in the US beginning in 1986. The analysis included men diagnosed with nonmetastatic prostate cancer between 1986 and January 2019 who had postdiagnostic dietary data available. Participants completed validated food-frequency questionnaires every 4 years, allowing investigators to estimate intake of saturated, monounsaturated, polyunsaturated, trans, animal, and plant-based fats.

The 4884 participants had a mean age of 69.5 years (SD, 6.9) at prostate cancer diagnosis. Among all patients, 97% were White, 62% had clinical T1 disease, and 10% had Gleason scores of 8 to 10. The median interval between diagnosis and completion of the postdiagnostic dietary questionnaire was 2.4 years (IQR, 1.5 to 3.5).

During a median 12.8 years of follow-up, 3040 deaths occurred, including 803 from cardiovascular disease, 499 from cancers other than prostate cancer, and 441 from prostate cancer.

In addition to the increased all-cause mortality associated with higher saturated fat intake, saturated fat was associated with cardiovascular mortality (HR, 1.42; 95% CI, 1.02 to 1.98) and mortality from other cancers (HR, 1.42; 95% CI, 0.93 to 2.17). Higher animal fat intake, a major source of saturated fat, was also associated with all-cause mortality (HR, 1.14; 95% CI, 0.97 to 1.33) and other cancer mortality (HR, 1.49; 95% CI, 1.00 to 2.21).

Notably, investigators did not identify an association between postdiagnostic dietary fat intake and prostate cancer-specific mortality.

The investigators also conducted nutrient-density substitution analyses. Replacing 10% of calories from animal fat with plant-based fat was associated with a lower risk of all-cause mortality (HR, 0.84; 95% CI, 0.76 to 0.93). Replacing 5% of calories from saturated fat with monounsaturated fat was similarly associated with lower all-cause mortality (HR, 0.80; 95% CI, 0.70 to 0.91).

“The central message is not simply to ‘eat less fat’. Rather, the type and source of fat appear to matter,” explained co-senior author David P. Labbé, PhD, scientist in the Cancer Research Program at The Institute and associate professor in the Department of Surgery at McGill University, in the news release.² “Replacing some animal fats and saturated fats with plant-based and unsaturated fats may help support long-term health after a prostate cancer diagnosis.”

Co-senior author Edward Giovannucci, MD, ScD, professor of nutrition and epidemiology at Harvard T.H. Chan School of Public Health, also added, “The takeaway is to prioritize simple substitutions—choosing olive oil, nuts, seeds, avocados, and other plant-based foods more often instead of foods high in animal or saturated fat.”

Limitations and interpretation

The author acknowledged several limitations of the study, including its observational design, which introduces the potential for residual confounding. Further, the study cohort was composed predominantly of patients who self-reported as White and were health professionals, which may limit generalizability.

However, for urologists, the findings may provide additional evidence to support general cardiovascular and survivorship counseling, particularly for men with substantial cardiometabolic risk.

Labbé concluded, “Ultimately, our goal is to make nutrition a more precise and evidence-based component of prostate cancer care—one that takes into account the treatment received, tumor biology, and each patient’s cardiovascular and metabolic health.”

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