Using the health star-rating for packaged food should be simple, but it's not

New Zealand does have a healthy food ranking system, but it's full of flaws, confusing for shoppers, and easy for manufacturers to get around

The Food Health Star Rating system is supposed to guide our choices when it comes to packaged food.

But since its introduction 13 years ago it's faced a galaxy of issues, including manufacturers who've managed to get around it, and consumer confusion.

Improvements have been slow.

Critics say the voluntary system gives the food industry a free pass, because they can cherry-pick their ratings, and avoid using it for less healthy products.

Belinda Castles, who is a research and test writer at Consumer NZ, wants to see the Food Health Star Rating system made compulsary for manufacturers.

"Because if they're not mandatory," she asks, "why would they bother?"

Today on The Detail we look at how - and if - the system works.

It was introduced in 2011 by the government so kiwis could measure the healthiness of their food.

The system uses a rating scale of 0.5 to five stars. When comparing similar foods, foods with more stars are deemed to be healthier than foods with fewer stars.

Sounds simple, but the implementation has been far from it.

From Nestle giving its Milo powder a 4.5 star rating despite being almost 50 percent sugar to chocolate milk being rated healthier than regular milk, the trans-Tasman system has had no shortage of critics.

Castles and says there was a lot of confusion in the early days among shoppers over how to actually use the system.

"It's intended for packaged foods, so it shouldn't be a substitute for following the healthy eating guidelines." she says.

Castles also says the system also rates products based on their category.

"You can't compare apples and pears because the calculation's different. So you should look at the cereal aisle and go 'right, within this category I can look at the different ratings, but I can't compare that box of cereals with a box of crackers or a bottle of cooking oil'," she explains.

But even when comparing products within the same category, things don't seem to add up. Nutrigrain has a four star rating. But in just one cup, which is the recommended serving size, there are over nine grams of sugar, almost a third of the public health recommended daily intake.

Professor of Population Nutrition and Global Health at the University of Auckland, Boyd Swinburn, is critical of the system. …

Go to this episode on rnz.co.nz for more details