Abstract
Health-oriented dietary transition is an important component of sustainable food systems, but greater dietary diversity or a higher animal-source-food share does not necessarily indicate closer adherence to dietary recommendations. Existing indices such as the Healthy Eating Index and Chinese Healthy Eating Index require individual-level dietary, energy, or detailed food-subgroup data. This study therefore developed a partial, food-group-based Nutritional Alignment Index (NAI) for repeated provincial monitoring; it complements rather than replaces validated individual-level diet-quality indices. Methodologically, this study adopts a province-level quantitative panel design based on secondary official statistical data. The 31 mainland provincial-level units are included as complete mainland provincial coverage rather than as a probabilistic sample, yielding 310 province-year observations for the overall-resident analysis. The analysis combines guideline-based index construction, province-paired tests, regional disparity measures, and robustness checks. Using provincial food-consumption data for 31 mainland Chinese provinces from 2015 to 2024, the study compared nine observable food groups with recommended intake ranges in the Chinese Dietary Guidelines (2022). Province-paired tests showed that the NAI increased from 0.698 to 0.738 for overall residents (change = 0.040, 95% CI [0.026, 0.054], p < 0.001) and from 0.631 to 0.697 for rural residents (change = 0.066, 95% CI [0.053, 0.078], p < 0.001); the urban change from 0.754 to 0.765 was not statistically significant ( p = 0.114). Central and western provinces improved faster than eastern provinces, and the urban–rural gap narrowed significantly. Component results revealed persistent dairy insufficiency and deteriorating livestock-and-poultry-meat alignment despite improvements in fruits, eggs, aquatic products, grains, and vegetables. The positive overall direction remained under fixed population weighting, exclusion of sugar, alternative component weights, one-sided vegetable and cooking-oil rules, quadratic penalties, and leave-one-component-out checks, although the magnitude was sensitive to the penalty function. The findings distinguish structural upgrading from nutritional alignment and support region- and food-group-specific interventions. The novelty of the study lies in distinguishing structural dietary upgrading from guideline-based nutritional alignment at the province-year level. The findings suggest community-level nutrition education and dietary guidance, region-specific policy support for under-consumed recommended foods, and future research combining micro-level dietary surveys with environmental-impact assessment.