Suboptimal diets contribute significantly to global mortality, surpassing other risk factors across demographics. Supermarkets, with their accessibility, comprehensive food inventories, and increasing integration of healthcare services (e.g., registered dietitians, online shopping), offer a promising setting for dietary interventions. This study aimed to test the effectiveness of two interventions, both involving in-person, dietitian-led education guided by participants' purchasing data: one focusing solely on the in-store environment (Strategy 1) and the other incorporating online shopping tools, home delivery, and other digital resources to enhance dietary choices (Strategy 2). The importance of this study lies in its novel approach of collaborating with a major supermarket chain to rigorously evaluate comprehensive healthcare interventions, thus addressing the pressing public health challenge of unhealthy diets. Limited prior research exists on rigorous testing of such collaborative strategies in improving dietary quality. This approach promises to combine the convenience and accessibility of supermarkets with the potential of digital tools for personalized nutrition education and support. This would expand healthcare beyond traditional settings and tackle diet-related health issues effectively.

Existing research highlights the effectiveness of dietitian-led nutrition counseling in supermarket settings. Studies have explored the potential of incorporating online shopping and mobile apps to improve dietary habits. The Dietary Approaches to Stop Hypertension (DASH) diet has been extensively studied and shown to improve cardiovascular health outcomes. However, widespread adoption of DASH remains low, highlighting the need for innovative approaches to bridge this gap. Prior research indicates significant correlations between DASH score improvements and decreased mortality risks from various causes, emphasizing the clinical importance of promoting DASH diet adherence. While controlled feeding studies have shown the effects of DASH, studies involving free-living populations have demonstrated impact through intensive programs conducted in academic centers. The American Heart Association (AHA) continues to recommend evidence-based, heart-healthy dietary patterns like DASH, yet adoption remains low, underlining the urgent need for innovative interventions. This study contributes to the existing literature by rigorously evaluating a combined supermarket and web-based approach to promote the DASH diet, utilizing participants' real-world shopping data.

The SuperWIN trial was a randomized, parallel-assignment, active-control, efficacy trial (NCT03895580) involving 267 participants (247 in the final analysis after excluding those affected by the COVID-19 pandemic interruption). Participants were recruited from a large retail supermarket chain's customer base. Inclusion criteria included at least one cardiovascular risk factor (hypertension, obesity, hypercholesterolemia) and eligibility to receive up to two $25 incentives. Following a run-in period, participants were randomized (2:2:1 ratio) to Strategy 1 (in-store education only), Strategy 2 (in-store education plus online tools), or an enhanced control group (standard medical nutrition therapy). The study used a stratified randomization list, stratified by age, gender, and household size. The primary outcome was change in DASH score (0–90 scale, higher score indicating better adherence) measured at 3 and 6 months using three 24-hour dietary recalls. Secondary outcomes included blood pressure, BMI, and lipid levels. Data were analyzed using intention-to-treat analysis, mixed models for repeated measures, and multiple imputation for missing data. Power analysis was conducted to ensure sufficient sample size to detect significant differences in DASH scores. The study adhered to a hierarchical hypothesis testing approach to maintain experiment-wise error rate.

All three groups showed improvements in DASH scores from baseline to 3 months, with greater improvements in the intervention groups. At 3 months, the combined Strategies 1 and 2 resulted in a significantly higher increase in DASH score (4.7 points, 95% CI [0.9, 8.5], P=0.02) compared to the control group. Strategy 2 led to a significantly higher DASH score increase compared to Strategy 1 (3.8 points, 95% CI [0.8, 6.9], P=0.01). This difference was attributed in part to a significant increase in fruit servings in Strategy 2 compared to Strategy 1. At 6 months, the benefits of the interventions on DASH scores persisted, although the difference between combined Strategies 1 and 2 versus control was no longer significant. Secondary endpoints (blood pressure, lipids, BMI) did not show significant between-group differences at 3 or 6 months, although both intervention strategies demonstrated reductions in SBP, DBP, and BMI compared to baseline. Pre-pandemic subgroup analysis showed similar trends, with Strategy 2 showing better results than Strategy 1, although this difference was not statistically significant at 6 months. Subgroup analysis showed greater DASH score improvements in older participants, white participants, and those with baseline hypertension.

The SuperWIN trial demonstrates that supermarket-based dietary interventions, particularly when enhanced with online tools, can effectively improve dietary quality in a free-living population. The significant increase in DASH scores, particularly with Strategy 2, highlights the potential of combining in-person education with digital technologies to overcome barriers to healthy eating. The persistence of improved DASH scores at 6 months suggests long-term benefits. While secondary outcomes did not show significant between-group differences, the observed improvements within the intervention groups are encouraging. The high participant engagement, even during the COVID-19 pandemic, underscores the appeal and accessibility of this intervention model. The study's findings support the importance of collaborative research between academia and the retail industry to develop and test effective public health interventions. The results suggest that even small increases in diet quality can have significant positive effects on health outcomes. Future studies could focus on enhancing long-term adherence through additional visits or telehealth support, and on evaluating the impact on secondary outcomes in more detail.

This study shows that combining in-person, dietitian-led education with online tools improves DASH diet adherence, demonstrating the value of integrating technology into supermarket-based interventions. Future research should focus on sustaining these improvements long-term and on evaluating the impact on secondary outcomes. The findings highlight the potential for collaborative research between academia and the retail industry to enhance public health initiatives targeting dietary improvement. The success of this trial emphasizes the potential of supermarket partnerships to improve health outcomes at scale.

The study population was predominantly middle-aged, female, and from households with relatively high incomes, limiting the generalizability of findings to other demographics. The COVID-19 pandemic affected study conduct, potentially influencing participant engagement and data collection. The study's reliance on self-reported data (dietary recalls, medication use) could introduce bias. Furthermore, the limited number of blood pressure measurements may have reduced the precision of blood pressure assessments. Future studies could address these limitations by including more diverse populations, employing more rigorous data collection methods, and incorporating additional health behavior components (exercise, medication adherence).