Impacts of sugar and sweetener warning labels on substitution between sugar- and non-sugar-sweetened beverages in a non-hypothetical selection task.

Background: Front-of-pack (FOP) warning labels have demonstrated effectiveness for reducing sugar-sweetened beverage (SSB) consumption and switching to water. However, an unintended consequence is that they may also increase switching to non-sugar-sweetened beverages (NSSBs). A non-hypothetical experimental study examined the effectiveness of combining sugar and sweetener FOP warning labels to reduce sugary drink consumption and prevent NSSB substitution. The study also examined potential integration with Australia and New Zealand's existing Health Star Rating (HSR) system to determine suitability for local context and other jurisdictions with interpretive labelling schemes already in place.

Methods: Participants (N = 414) accessed an online convenience store app via an on-campus laptop to select one drink from an array of 10 beverages, on three occasions. Drink options included a variety of SSBs, 100% fruit juice, NSSBs, and water. Following an escalating exposure procedure, drinks were presented (1) without any additional labelling, (2) with warning labels added to sugary drinks or to both sugary drinks and NSSBs (according to allocated condition), then (3) with HSR icons added to all drinks. Participants were informed they would receive a complementary drink, based on their selections, following the completion of a brief questionnaire.

Results: Baseline results indicated that SSBs and water were the most and least popular drink choices, respectively. Placing FOP warning labels on sugary drinks decreased selection of SSBs and increased NSSB and water choices. Water became the most popular individual drink choice in response to warnings on sugary drinks. Placing FOP warning labels on both sugary drinks and NSSBs successfully avoided an increase in NSSB choices, whilst also increasing water selections, but did not significantly decrease selection of SSBs until HSR ratings were added. The incorporation of HSR icons consolidated warning label effects on NSSB and water selection across both conditions.

Conclusions: Results demonstrate the potential of FOP sugar warning labels for addressing beverage consumption behaviours. The incorporation of sweetener warning labels may successfully avoid substitution towards NSSBs, whilst still promoting water choices, but may also dilute the impact of the sugary drinks warning labels. Warning labels were complementary to existing interpretive FOP labels.