Authors’ response: Regarding the paper ‘The impact of a supermarket nutrition rating system on purchases of nutritious and less nutritious foods’ by Cawley et al.

Madam

Nutrition guidance systems are widely seen as a potential way of facilitating healthier diets, but they remain under-studied. The Guiding Stars nutrition rating system is one promising approach. In contrast to the Nutrition Facts panel, which was mandated by US federal law, Guiding Stars is a voluntary, private-sector solution to the problem of consumers having imperfect information at the point of purchase. The Guiding Stars system both gives consumers information that facilitates healthier choices and gives food manufacturers a reason to reformulate their products to make them healthier and earn one, two or three stars^{( 1 )}. The Guiding Stars system, and others like it, demonstrates that food marketing does not have to make us fat^{( 2 )}.

Our analysis shows that Guiding Stars was successful in its objective of helping consumers make healthier decisions when food shopping^{( 3 )}. We found that the percentage of food purchases rated as nutritious (starred) rose by 1·39 % (P<0·01) after the Guiding Stars system was introduced into Hannaford. Drilling down, we found that shoppers bought a similar amount of nutritious (starred) products, but fewer non-nutritious (unstarred) products. Improving this ratio was an objective of Guiding Stars and the stores in which it was implemented^{( 4 , 5 )}.

In the data we were generously (and unconditionally) provided by Hannaford – which did not contain sales from non-food items, which can be a sizeable amount of grocery sales – we found that there was a net decrease in sales of food. We were interested to see, in the letter of the Guiding Stars’ Scientific Advisory Panel to the Editor of this journal, that total sales (which include non-food items) increased. This suggests that nutrition guidance systems may both be good for consumer diets and sustainable for business.