The findings published in the American Journal of Epidemiology found patients who regularly ate the highest amounts of omega-3 fish oil were between 34 to 40 per cent less likely to die from the disease.
A 20-year-long study at the Harvard School of Public Health in Boston also found that patients who consumed very high amounts of saturated fats were twice as likely to die from their tumour compared to those who ate less, the 'Daily Mail' reported.
According to the study, the risks of prostate cancer increase with age and men over 50 are more likely to develop a tumour, which has a strong genetic element to it.
Scientists tracked 525 men with an average age of 70 who had signed up to a long-term study back in 1989 after being diagnosed with prostate cancer. Patients were quizzed on their dietary habits, including consumption of different types of fats.
For the next 20 years, all the men were followed up to monitor survival rates.
The results showed that, by March 2011, 222 of the men had died from prostate cancer and 268 from other causes.
When researchers compared the causes of death with dietary habits they found men who regularly ate fish with high oil content were between 34 and 40 per cent less likely to have died from their prostate cancer.
The researchers said diet appears to have a powerful effect on tumours that are in the early stages of development.
"Fish consumption may have a modest protective effect on prostate cancer risk and progression, as well as disease specific mortality. These results suggest early stage tumours may be more responsive to dietary factors and that diet may influence prognosis following a diagnosis of early stage prostate cancer," the researchers were quoted by the paper as saying.
Last year's study, carried out at the University of California found fish oil reduced the number of rapidly dividing cells in the prostate cancer tissue, potentially reducing the chances of the disease spreading to other parts of the body.
