New research suggests that eating a western diet after a prostate cancer diagnosis could increase the risk of mortality.

Researchers at Harvard University found that eating a diet higher in red and processed meat, high-fat dairy foods, and refined grains could lead to a significantly higher risk of both prostate cancer-related mortality and overall mortality compared with eating a diet rich in vegetables, fruits, fish, whole grains, and healthy oils

"There is currently very little evidence to counsel men living with prostate cancer on how they can modify their lifestyle to improve survival. Our results suggest that a heart-healthy diet may benefit these men by specifically reducing their chances of dying of prostate cancer," Jorge Chavarro, senior author of the study, said in a statement.

For the study, researchers looked at health and diet data from more than 900 men participating in the Physicians' Health Study I and II who were diagnosed with prostate cancer. They followed the men for an average of 14 years after their diagnosis, grouping them into quartiles according to whether they followed a Western dietary pattern or a "prudent" (higher consumption of vegetables, fruits, fish, legumes, and whole grains) dietary pattern.

They found that men who ate mostly a Western diet had two-and-a-half times higher risk of prostate cancer-related death -- and a 67 percent increased risk of death from any cause. Men who ate mostly a "prudent" diet had a 36 percent lower risk of death from all causes.

"These results are encouraging and add to the scant literature on this area, but it is important to keep in mind that all study participants are physicians and most are white. Therefore it is very important that our results are replicated in other studies with more diverse socioeconomic and racial/ethnic backgrounds," Meng Yang, lead author of the study, said in a statement.

The findings are detailed in the journal Cancer Prevention Research.