Digital platforms increasingly expose Malaysian consumers to foods promoted with health claims, yet limited evidence explains how advertising cues relate to purchase intention in environments where product credibility can be difficult to judge. Drawing on the Theory of Planned Behaviour and the Stimulus-Organism-Response framework, this study investigated how digital stimuli relate to purchase intention through attitude, subjective norm, overall evaluation, and perceived behavioural control, while also examining the role of food literacy. A quantitative cross-sectional survey was conducted among 225 Malaysian digital consumers recruited through targeted Facebook advertisements. Data were analyzed using Partial Least Squares Structural Equation Modelling, with food literacy operationalized as regulatory knowledge and assessed separately through dichotomously scored items. The findings showed that digital stimuli were positively associated with all four psychological mechanisms, which in turn predicted purchase intention. Overall evaluation emerged as the strongest predictor, followed by attitude, subjective norm, and perceived behavioural control, highlighting the importance of consumers' appraisals, social environment, and perceived capacity to act when responding to digitally promoted health claims. Food literacy was not associated with purchase intention, indicating that factual knowledge of food regulations and claim requirements alone may be insufficient to shape purchasing responses within persuasive digital marketing environments. The study extends the integrated framework by demonstrating that purchase intention toward health-claimed foods is more directly associated with evaluative and behavioural mechanisms than with regulatory knowledge alone. The findings support clearer claim communication and consumer interventions that combine regulatory knowledge with practical claim-evaluation skills.