The diet recommends three tablespoons a day as part of an allowance of four to five servings of healthy fats that include EVOO, nuts, olives and avocado.
It also includes six to seven serves of wholegrain starch, at least four servings of vegetables, up to three optional serves of fruit, up to two optional of dairy and eggs, and 350g maximum meat, poultry or seafood a week — or no more than 170g a month.
The diet also eliminates cured meats and vegetable oils, margarine and mayonnaise with vegetable seed oils, saying they are linked to an increased cancer risk.
Flynn compared the diet recommended by the Prostate Cancer Foundation, which recommends decreasing carbohydrates, sugar, high fat foods, charred meats, increasing protein and allowing vegetable oil, margarine and salad dressings but no EVOO.
Men followed the two diets for eight weeks, and then were able to pick one to follow for six months and a follow up.
"Cardiovascular disease is the leading cause of death for prostate cancer patients," Flynn said.
"A plant-based EVOO diet improves insulin function and lowers fasting insulin and glucose levels, protects against weight gain and reduces the risk of various cancers."
Flynn's research also shows that people who had EVOO every day have lower rates of most chronic diseases, such as heart disease, cancers, arthritis, and type 2 diabetes.
"EVOO has been shown to decrease a number of risk factors for chronic diseases including inflammation, blood pressure, body weight, blood levels of insulin and glucose, oxidation, and blood coagulation," Flynn said.
In Australia 20 per cent of men will be diagnosed with prostate cancer by the age of 85.
Cancer Australia says physical inactivity, high body mass index (BMI) and low fruit and vegetable consumption are among the modifiable risk factors that account for about one third of the total burden of cancer in Australia.
"The diet isn't just for cancer patients or prevention, it's for everyone wanting to live a healthy life, and prevent the risk of disease," Flynn said.
Her research was supported by Nutrition Australia and Cobram Estate as the olive harvest gets under way around the country.
Nutrition Australia chief executive Lucinda Hancock said the organisation had long recognised and promoted the benefits of a Mediterranean diet where extra virgin olive oil was a recommended healthy fat.