The new study, published in JAMA Internal Medicine, finds that men with non-metastatic prostate cancer have a significantly lower risk of the disease developing in to lethal forms of the cancer and of dying from other causes if they switch to a diet that is rich in vegetable fats such as such as olive and canola oils, nuts, seeds and avocados.
"The beneficial effects of unsaturated fats and harmful effects of saturated and trans fats on cardiovascular health are well known," explained Erin Richman from UC San Francisco, USA - who led the study.
"Now our research has shown additional potential benefits of consuming unsaturated fats among men with prostate cancer," she added.
The US-based team said that their findings could help with the development of new dietary guidelines for the disease - which millions of men around the world.
The research analysed data from almost 4,600 men with non-metastatic prostate cancer who took part in the the Health Professionals Follow-up Study between 1986 and 2010.
Richman and her team looked at the men's intake of saturated, monounsaturated, polyunsaturated and trans fats as well as fats from animal and vegetable sources.
During the study timeframe, 1,064 men died, primarily from cardiovascular disease (31%), prostate cancer (21%) and other cancers (nearly 21%).
However, further analysis by the team uncovered a striking difference between some groups of men - noting that those who replaced 10% of their total daily calories from carbohydrates with healthy vegetable fats had a 29% lower risk of developing lethal prostate cancer and a 26% lower risk of dying from all causes.
The team also found that adding a single serving of oil-based dressing a day was associated with a 29% lower risk of lethal prostate cancer and a 13% lower risk of death, while adding one serving of nuts a day was associated with an 18% decrease in death from prostate cancer and an 11% drop in all cause mortality risk.
"Consumption of healthy oils and nuts increases plasma antioxidants and reduces insulin and inflammation, which may deter prostate cancer progression," suggested Richman.