Key Points:

A new study has shattered the commonly held idea that healthier foods cost substantially more.

Instead, the Auckland University study suggests that healthier eating for an average family of four can be obtained for just $7 more a week.

"Our research has shown that making some important healthier choices, such as eating chicken breast instead of drumsticks or drinking low-fat milk rather than full-fat, would only make about a $7 difference in a weekly family shop," said Dr Cliona Ni Mhurchu from the university's clinical trials research unit.

"This should not cause a major impact on the diet in terms of taste or choice, but could have important health benefits."

The unit based its finding on electronic sales data from 882 supermarket shoppers from one Wellington supermarket. Their purchases were followed over a 12-month period, with the 88 top-selling staples used to create two different shopping baskets.

The baskets did not differ substantially in overall cost, with the basket of healthier options costing just $6.42 a week more for a household of two adults and two children aged five and 10.

But the healthier supermarket items also contained about a third less energy and fat, and half the sugar and saturated fat.

The healthier options, however, were substantially more expensive in certain categories, particularly low-fat spreads (compared to butter), and leaner cuts of meat and poultry.

But some foods, such as canned fish and breakfast cereals and breads, were cheaper when healthier substitutes were chosen.

"People in general believe that things like wholemeal bread cost more," Dr Ni Mhurchu said.

"It was interesting for us to see that for a lot of the real staple food groups, you can make healthy choices that won't cost an awful lot more. But it has to be qualified that this wasn't really looking at an average diet for a family because it excludes fruit and vegetables as a major food group and we know they tend to cost a fair bit."

The study appears in the latest New Zealand Medical Journal. An accompanying editorial by public health researchers at Otago University urges for action to reduce the price of healthy foods.

It suggests the Government consider schemes such as providing vouchers for fruits and vegetable discounts for low-income families and a mandatory traffic light system for foods as a simple way of indicating a food's health benefit or detriment.

Next month, Dr Ni Mhurchu will start recruiting 1200 supermarket shoppers for a Wellington trial looking to see if a discount of 12.5 per cent (the rate of GST) on healthier foods will spur people to buy more healthy foods.