Substitute or complement? Quantity–quality effects of agricultural production diversity and market access on diets

In many developing countries, rural households meet their food needs through both self-production and market purchases, but evidence on the relative and joint roles of these channels in shaping dietary diversity and dietary quality remains limited. Using household panel data from rural China spanning 2004–2011, we provide micro-level evidence from a major developing-country context to examine the quantity–quality effects of agricultural production diversity, market access, and their interaction on dietary diversity and dietary quality. Fixed-effect models combined with an instrumental-variable strategy are used to address potential endogeneity. We find that both greater production diversity and improved market access enhance dietary diversity and dietary quality. A one-standard-deviation increase in agricultural production diversity raises the dietary diversity score and the Chinese Healthy Eating Index by 0.5 and 0.71 standard deviations, respectively. Similarly, reducing the distance to markets by one standard deviation increases both outcomes by 0.03 standard deviations. Further analysis reveals an overall substitution relationship between production diversity and market access in improving dietary outcomes. The marginal contribution of production diversity on dietary diversity and quality diminishes as market access improves, and vice versa. At the food-group level, however, functional complementarity exists between these two channels for soybeans and nuts, vegetables, and aquatic products. Diversified production supports higher intake of these foods when market access is limited, while better market access attenuates reliance on self-produced items by expanding access to a broader set of foods. Taken together, the findings highlight the continued importance of agricultural production diversification in improving diets where markets are thin, and underscore the critical role of improving market conditions, particularly in regions such as Africa and South Asia with persistently high market frictions.