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More health stars doesn't necessarily mean healthier food

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Checking how many health stars food items have is a good habit, but don’t read too much into them.

QUESTIONOn a trip to the supermarket I bought smoked salmon that had health stars. Nutella, I noticed, had 1 star and jam had 2½. That doesn’t seem to make sense. Please explain the star-rating system and whether it takes anything else besides salt and saturated fat into account.

ANSWERThe more stars, the healthier the food”, the Ministry for Primary Industries (MPI) states on its How Health Star Ratings Work web page. However, you’ll need to read the fine print to put that advice into context.

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For a start, the health-star ratings system is not designed for the comparison of foods from different categories. So comparing jam’s rating with a fish product’s is meaningless. Instead, the system is for weighing up the merits of products within the same category. So, for example, among nut butters, Nutella scores 1 star but Sanitarium’s peanut butter without added sugar or salt has 4½ stars. Clearly, the peanut butter is healthier than the Nutella.

The system scores foods based on the presence of a limited range of nutrients and ingredients. Energy content, levels of risky nutrients such as saturated fat, sodium and total sugar, the amounts of beneficial components such as dietary fibre and protein and the proportions of fruits, vegetables, nuts and legumes are taken into account. More points means more stars.

Sanitarium’s peanut butter has 10% of the saturated fat, sugar and sodium of Nutella, which helps explain why it scored more stars.

In the case of salmon, the rating can vary depending on how the fish is processed. Tinned and fresh salmon get 4 stars compared with the cold-smoked variety’s 1½ stars.

Steve Hathaway, MPI’s director of food science and risk assessment, says, “This is largely due to its sodium content. Prior to smoking, salmon is cured in a brine that results in a high sodium content.”

Indeed, cold-smoked salmon has 950mg of sodium per 100g, compared with 52mg in fresh salmon, or 487mg in tinned salmon.

So, by all means check and compare the health-star ratings on foods in the same category. You have a good chance of making a healthier decision if you choose the product with the greater number of stars. But the system tells you nothing useful when comparing dissimilar foods.

This article was first published in the August 25, 2018 issue of the New Zealand Listener.