Eating some of them raw may also reduce their cancer-fighting compounds.

Minister for Primary Industries, Fisheries and Rural and Regional Queensland Tim Mulherin said this new research is significant to the Q2 ambition of making Queenslanders Australia's healthiest people.

Researchers found that to maximise the anti-cancer properties of brassica vegetables, including broccoli, cabbage and cauliflower, they should be steamed or stir fried for two to four minutes, or microwaved for no more than two minutes.

"I am encouraging everyone to take on board this important message about how to get the most out of their vegetables," Mr Mulherin said.

Researcher David Williams from the Department of Employment, Economic Development and Innovation has completed a PhD on this topic.

Mr Williams said light cooking reduced the occurence of compounds called "nitriles".

"Nitriles do not protect against cancer and in fact replace anti-cancer compounds," he said.

"But cooking these vegetables on a very low heat for a short time stops the nitriles and allows the release of anti-cancer compounds.

"The exception to this rule is the brassica vegetables that are naturally hot to the taste - such as radish, mustard or watercress. They are best eaten raw to maximise the anti-cancer compounds."

The research has been conducted by scientists from the Department of Employment, Economic Development and Innovation and The University of Queensland.

Fast facts

• Historical ly brassica vegetables come from many parts of the world with many emanating from Asia and Europe
• The main growing areas in Queensland include the Lockyer Valley (winter production) and the Granite Belt (Stanthorpe) and the Darling Downs (summer)
• Broccoli production alone was valued at $23million in Queensland (2008-09)