New Zealand should adopt a world standard food rating system to help to protect children from exposure to the marketing of unhealthy food, according to Auckland University research.

LISTEN ABOVE: Caryn Zin, Nutritionist and Dietitian, speaks with Rachel Smalley

The study looked at three accepted nutrient profiling systems and found the World Health Organisation Europe's model to be the most effective.

Lead author Professor Cliona Ni Mhurchu says the WHO system needs to underpin the Advertising Standards Authority's revised Children's Code for Advertising Food.

"Promotion of unhealthy foods and drinks is a significant, modifiable risk factor for child obesity and diet-related non-communicable diseases," she said.

The ASA is reviewing the code for advertising food to children. It called for submissions in February and the review's final recommendation is expected in September.

The Auckland University study, published in the New Zealand Medical Journal, also also looked at the Health Star Rating and the Ministry of Health Food and Beverage Classification System.

Researchers examined 13,066 items of packaged food and determined the proportion and types that met the criteria for all three system or for none of them.

Prof Ni Mhurchu said the HSR and FBCS systems would permit marketing of a number of food products of concern, particularly high-sugar breakfast cereals, fruit juices and ready meals.

She said the effectiveness of the new code should be evaluated by an independent body.

However, the only way the revised code could begin to be effective was to adopt an accepted nutrient profiling system.