Using a Naturalistic Store Laboratory for Clinical Trials of Point-of-Sale Nutrition Policies and Interventions: A Feasibility and Validation Study.

Point-of-sale policies such as warnings and taxes are promising tools for improving the nutritional quality of food purchases. Research studies conducted in naturalistic store laboratories could improve the quality of evidence about point-of-sale interventions by allowing for realistic exposure in a controlled setting. This study aimed to assess whether purchasing behavior in a naturalistic store laboratory setting was similar to real-life purchasing behavior and to evaluate participants' perceptions of store realism and the acceptability of research study protocols in this setting. In a longitudinal observational study in 2019, Latinx parents in North Carolina (n = 61) attended five weekly visits at the UNC Mini Mart, a naturalistic store laboratory that resembled a small convenience store. At each visit, participants purchased a week's supply of beverages. Purchases of beverages in the Mini Mart were compared to participants' purchases from receipts submitted the week prior to the study. Analyses compared the percentage of participants buying sugary drinks and non-sugary drinks in the Mini Mart vs. in real stores using Chi-Square tests with Fisher's p. The percentage of parents who purchased sugary drinks in the Mini Mart (93%) was not significantly different from the percentage who purchased sugary drinks during the week before the study (74%, p = 0.28). The percentage purchasing non-sugary drinks was similar in the two settings (85% in the Mini Mart vs. 85% from receipts, p = 0.33). Nearly all participants reported that their Mini Mart purchases were similar to real-life purchases (96%); the Mini Mart felt like a real store (94%); they could find all the beverages they were looking for (92%); and they could imagine doing their real-life beverage shopping in the Mini Mart (92%). Moreover, retention was high, with 97% of participants attending the final study visit. These results indicate that naturalistic store laboratories are a promising method for increasing the ecological validity of trials to evaluate point-of-sale interventions.