The effect appears to be slightly stronger with regard to more aggressive forms of the disease, found investigators at Fred Hutchinson Cancer Research Center in US.
While previous studies have suggested that eating foods made with high-heat cooking methods, such as grilled meats, may increase the risk of prostate cancer, this is the first study to examine the addition of deep frying to the equation.
Researchers found that men who reported eating French fries, fried chicken, fried fish and/or doughnuts at least once a week were at an increased risk of prostate cancer as compared to men who said they ate such foods less than once a month.
In particular, men who ate one or more of these foods at least weekly had an increased risk of prostate cancer that ranged from 30 to 37 per cent.
Weekly consumption of these foods was associated also with a slightly greater risk of more aggressive prostate cancer.
"The link between prostate cancer and select deep-fried foods appeared to be limited to the highest level of consumption - defined in our study as more than once a week - which suggests that regular consumption of deep-fried foods confers particular risk for developing prostate cancer," researcher Janet L Stanford said.
Possible mechanisms behind the increased cancer risk, Stanford hypothesises, include the fact that when oil is heated to temperatures suitable for deep frying, potentially carcinogenic compounds can form in the fried food.
They include acrylamide (found in carbohydrate-rich foods such as French fries), heterocyclic amines and polycyclic aromatic hydrocarbons (chemicals formed when meat is cooked at high temperatures), aldehyde (an organic compound found in perfume) and acrolein (a chemical found in herbicides).
These toxic compounds are increased with re-use of oil and increased length of frying time. Foods cooked with high heat also contain high levels of advanced glycation endproducts, or AGEs, which have been associated with chronic inflammation and oxidative stress.
Deep-fried foods are among the highest in AGE content. For example, chicken breast deep fried for 20 minutes contains more than nine times the amount of AGEs as a chicken breast boiled for an hour.
For the study, Stanford and colleagues analysed data from two prior population-based case-control studies involving a total of 1,549 men diagnosed with prostate cancer and 1,492 age-matched healthy controls.
The men were Caucasian and African-American Seattle-area residents and ranged in age from 35 to 74 years.
