Background:NuVal, developed by NuVal, LLC, is a shelf nutrition label that rates the nutritional quality of foods on a scale of 1 (worst) to 100 (best). Objective:The objective of this study was to explore the impact of the NuVal labels on food-purchasing patterns. Design:In 2014, NuVal updated its nutrient profiling system, which changed the NuVal score on many foods. We took advantage of this "natural experiment" to assess the extent to which a change in the NuVal score influenced purchases of yogurts, a category with a wide range of more and less healthy alternatives. We supplemented these data with a survey of consumers in stores using NuVal labels to obtain their experience with the labels and the extent to which they state that the labels influence their purchases. Results:Results suggested that a 1-point increase in the NuVal score is associated with a 0.49% increase in sales. Because only 8% of survey respondents reported using NuVal to influence dairy purchases, the impact of a change in the score among users may be >10 times the average effect. Conclusion:Results suggest that front-of-package nutrition labels are likely to influence purchasing patterns. This trial was registered at www.clinicaltrials.gov as NCT03390075.