For many men with nonmetastatic prostate cancer, treatment is only one part of the bigger health picture. Because they often live for many years after diagnosis, heart health and other chronic conditions can become just as important.
A new study suggests diet may play a role. Researchers followed nearly 5,000 men with nonmetastatic prostate cancer and found that those who ate the most saturated fat after diagnosis had a higher risk of dying during follow-up than those who ate the least. The difference was driven mainly by cardiovascular disease rather than prostate cancer itself.
The study, published in JAMA Network Open, also found that diets higher in monounsaturated and plant-based fats were linked with better overall survival. Because this was an observational study, it cannot prove that changing the type of fat someone eats will extend life.
Still, the findings point to a useful message: the goal may not be to simply eat less fat, but to pay more attention to the type of fat and what foods it comes from.
Researchers followed 4,884 men for a median of nearly 13 years. The average age at diagnosis was about 70, and most participants were white male health professionals in the U.S. They completed food questionnaires that allowed researchers to estimate how much saturated, monounsaturated, polyunsaturated, trans, animal and plant-based fat they ate after diagnosis.
During the study, 3,040 men died. Cardiovascular disease accounted for 803 deaths, while 441 deaths were attributed to prostate cancer.
Men in the highest group for saturated fat intake had a 24% higher rate of death from any cause than men in the lowest group. In more concrete terms, the researchers estimated that about 26 out of 100 men with the highest saturated fat intake would die within 10 years, compared with about 23 out of 100 in the lowest group.
That difference was not mainly about prostate cancer. The researchers found no clear link between the type of dietary fat and death specifically from prostate cancer.
Instead, cardiovascular disease appeared to be a major part of the story.
That matters because men with nonmetastatic prostate cancer may live long enough for other health risks to become more important over time. As co-senior author Lorelei Mucci of the Harvard T.H. Chan School of Public Health noted in the news release, “Protecting cardiovascular and overall health is an essential part of prostate cancer care.”
The researchers also used statistical models to look at what might happen when one type of fat replaces another.
Replacing 10% of daily calories from animal fats with plant-based fats was associated with a 16% lower rate of death from any cause. Replacing 5% of calories from saturated fat with monounsaturated fat was associated with a 20% lower rate of death.
Those numbers are estimates, not promises. The men were not assigned different diets, so the study cannot show that making a specific food swap will reduce an individual person's risk by exactly that amount.
But the results do support a broader idea that has also appeared in heart-health research: replacing some foods high in saturated fat with foods rich in unsaturated fats may be a healthier choice over time.
In practical terms, that could mean using olive oil more often, adding nuts or seeds, or choosing avocado and other plant-based fat sources more regularly. The paper notes that common sources of saturated fat in U.S. diets include cheese, butter, high-fat dairy products, processed meats, beef and many desserts.
Co-senior author David P. Labbé of McGill University summed it up this way: “The central message is not simply to ‘eat less fat.’ Rather, the type and source of fat appear to matter.”
The study does have important limitations.
Men who ate more saturated and animal fat were also more likely to smoke, have a higher body mass index, exercise less and have diabetes. Researchers adjusted for those differences, but observational studies cannot completely rule out the possibility that other lifestyle or health factors helped shape the results.
Diet was also measured with food questionnaires, which depend on participants remembering and estimating what they ate. And because the main analysis used the first eligible diet questionnaire after diagnosis, it may not fully capture changes people made later.
The study population was another limitation. About 97% of participants were white, and all were male health professionals, so the findings may not apply equally to more diverse groups of men.
Even so, the study offers a useful reminder that life after prostate cancer is not only about the cancer itself.
For men with nonmetastatic disease, everyday choices that support heart and overall health may remain important for years after diagnosis. This research suggests that when it comes to dietary fat, what replaces what may matter more than simply cutting fat altogether.
The research was supported by the National Institutes of Health, the U.S. Department of Defense's Congressionally Directed Medical Research Programs and other academic and nonprofit research awards. Several authors reported relationships with pharmaceutical or health companies outside the submitted work, including consulting, advisory roles, research funding or equity interests.