Northern European or Anglo-Saxon diets higher in processed foods were associated with increased rates of prostate cancer.
The Mediterranean diet also had a low level of red meat and dairy consumption.
"We showed that dietary change to a Mediterranean-style diet is both achievable and beneficial for men with prostate cancer in New Zealand, albeit in a small and motivated group," Dr Bishop said.
"While there have been many studies looking at the impact of this diet on clinical indicators of disease, this is the first time such a study has been carried out in men with prostate cancer in New Zealand."
She said the study added credence to suggestions a low-inflammatory, high antioxidant diet could benefit men with prostate cancer.
Dr Bishop worked with nutritionist Sharon Erdrich.
The researchers evaluated a prostate-specific antigen -- a substance that caused immune systems to produce antibodies against it.
Evaluation on the antigen and on DNA damage was carried out at the study's start and after three months of following the diet. Dietary data was also collated from the men's diet diaries and a questionnaire.
A major reduction in DNA damage was found, especially where the men followed the Mediterranean-style diet closely and increased their consumption of pulses and green tea.
"This diet is most effective where men seek to improve their health outcomes and are willing to take on board new ways of eating," Dr Bishop said.
"It's not so much a prescriptive diet, but more a new way of eating."
She said the diet was not radically different from that of most Kiwis, except for fast food fiends.
In the study, other foods known to reduce inflammation including broccoli, pomegranate juice, salmon and green tea augmented the typical Mediterranean fare.
Dairy consumption was also kept within strict limits of one or two servings per day.
Dr Bishop said that at the three-month evaluation, DNA damage was related to how much dairy fat they consumed.
The research also found red meat consumption was linked to DNA damage.
Men in the pilot study were asked to limit their red meat consumption to Cancer Society recommendations of less than 500g per week. Fish or poultry filled the void for men used to eating more red meat.
Meanwhile, the classic summer barbecue was turned on its head as researchers asked men to not cook with high heat frying or barbecuing styles.
In an associated study, the researchers studied links between DNA damage and dietary fatty acid in the men with prostate cancer.
They found eating more oily fish and olive oil and less red meat, processed meats and dairy products resulted in a large reduction in DNA damage.
The researchers said prostate cancer was the fourth most common cancer internationally, and in men ranked second only to lung cancer.
In New Zealand, prostate cancer was the most commonly diagnosed cancer and third most common cause of cancer-related death.
Existing research linked diet and lifestyle factors to the development and progression of prostate cancer.
Death rates were higher for Maori men than men of other ethnicities.
Genetic and environmental factors, decreased antioxidant levels, and DNA damage were also blamed for causing prostate cancer.
The researchers said DNA damage was associated with the risk of various cancers and was "an ideal biomarker" for the assessment of the influence of foods on cancer.
The Ministry of Health and the Prostate Cancer Foundation said 600 men died from the disease here each year.
