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Changing one aspect of everyday diet could improve a patient with prostate cancer's chances of survival, a new study has suggested.
Experts at the Harvard T.H. Chan School of Public Health examined the association between dietary fat intake and mortality among patients with nonmetastatic prostate cancer—a specific clinical stage relating to the cancer.
They found that replacing animal and saturated fats, which includes red meat, butter and full-fat dairy, with plant-based and unsaturated alternatives, like olive oil and nuts, was associated with a notably lower risk of mortality among prostate cancer patients.
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Around 1 in 8 men will be diagnosed with prostate cancer at some point in their lifetime, according to the American Cancer Society, and there are around 333,000 new cases of the disease in the U.S. every year. It is the second-leading cause of cancer death in American men, behind lung cancer, and around 1 in 44 men will die of prostate cancer.
The study was published in the journal JAMA Network Open on September 2.
The findings "support what we have known that dietary fats seem to play a role in the development and progression of prostate cancer," Dr. Leonard Gomella, a professor of prostate cancer at Jefferson Medical College, told Newsweek.
"I find these findings encouraging because they suggest that practical dietary changes may improve long-term health for men with nonmetastatic prostate cancer," Dr. Arul Chinnaiyan, director of the Michigan Center for Translational Pathology, told Newsweek.
He added that "the key distinction is that the association was with overall survival; the study did not demonstrate fewer deaths from prostate cancer itself."
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What The Study Found
Almost 5,000 patients with nonmetastatic prostate cancer were involved in the study. Their mean age at the time of their diagnosis was around 69.5 years, and the median follow-up time was 12.8 years.
During follow-up, more than 3,000 patients passed away—around 400 from prostate cancer, around 500 due to other cancers and around 800 from cardiovascular disease.
They also found that higher saturated fat intake after cancer diagnosis was positively associated with all-cause mortality.
Even small adjustments in diet had notable impacts: replacing 5 percent of calories from carbohydrates with saturated fat or animal fat was associated with a higher risk for all-cause mortality for the prostate cancer patients, while replacing 5 percent of calories from saturated fat with monounsaturated fat or plant-based fat was associated with a lower risk.
Specifically, the researchers found that replacing 5 percent of calories from carbohydrates with saturated fats was associated with a 15 percent increase in overall deaths.
Their findings were similar to those in the Physicians’ Health Study, which included almost 1,000 patients with nonmetastatic prostate cancer. That study also found patients who replaced 10 percent of calories from animal fat with plant-based fat had a 44 percent lower risk of death.
Lorelei Mucci, lead author of the study and professor of epidemiology at Harvard University, told Newsweek she believed the finding was likely "multifactorial."
She said this was because dietary fats can impact blood lipid levels (cholesterol), which can affect cardiometabolic health, so "replacing saturated fats with plant-based or monounsaturated fats improves lipid profiles." She added "healthier forms of fat can lower blood pressure and the risk of metabolic syndrome."
Mucci said the findings were "an important message" and that it is "never too late to change to a healthier, more plant-forward diet, and that there are simple changes one can make. For example, using olive oil in cooking instead of butter, reducing intakes of red and processed meats for healthier protein sources, and using peanut butter or avocados on a piece of toast."
Why Could Plant-Based Fats Be Better For Prostate Cancer Patients?
Dr. Daniel Petrylak, a professor of medicine and urology at Yale University, told Newsweek that "high fat diets can result in increased markers of inflammation, which may accelerate prostate cancer growth."
"Reducing inflammation may reduce some of the signals associated with cancer progression," he said.
Petrylak also said that "one of the most common causes of death in men with prostate cancer is the result of cardiovascular disease," and so switching to a plant-based diet, which is healthier for the heart, "may account for the reduction in the death rate."
Chinnaiyan also said that plant-based fats like olive oil, nuts, and seeds, provide unsaturated fats that can lower LDL cholesterol when they replace saturated fats, which "offers a plausible pathway to better cardiovascular health."
Gomella said that he often tells his patients that "what is good for the heart is good for the prostate."
However, Chinnaiyan added that "the food source also matters because nuts and seeds provide fiber and other beneficial nutrients alongside their fats."
"We should be precise about the recommendation: coconut and palm oils are plant-derived but rich in saturated fat, so the emphasis should be on replacing saturated fats with unsaturated sources," he said.
What The Findings Could Mean
Chinnaiyan said that many men with nonmetastatic prostate cancer live for years or decades after diagnosis, "making their cardiovascular health an important determinant of long-term survival."
Given that in the study cardiovascular disease accounted for more deaths than prostate cancer, he said that "these findings emphasize the value of caring for the whole patient throughout prostate cancer survivorship."
"The good news here is that men can make a difference in their prostate cancer outcome after diagnosis by altering their dietary intake," Gomella said. "These findings validate existing recommendations from various medical groups about dietary fat and prostate cancer."
"For patients, these findings support making achievable substitutions, such as using olive oil in place of butter or ghee and replacing some foods high in saturated fat with nuts, seeds, or avocados," Chinnaiyan said, but added that "the evidence supports a potential overall health benefit, but we should not promise that these changes will slow prostate cancer or guarantee longer survival."
Reference
Mucci, L et al. (2026) Dietary Fat Intake and Mortality Among Patients With Nonmetastatic Prostate Cancer. JAMA Network Open. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2853518
Update 9/8/26, 9:05 a.m. ET: This article has been updated with comment from Lorelei Mucci.
Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang
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