Multiple indicators of household dietary diversity in rural China: Effects of income and dietary knowledge.

OBJECTIVE: The aim of this study was to examine the association among family income, dietary knowledge, their interaction, and the multiple household dietary diversity indices (HDDIs), including dietary diversity score (DDS), entropy index (EI), Shannon equitability index (SEI), Herfindahl index (HI), and Simpson index (SI). METHODS: Based on 24-h dietary recall data collected from 1076 rural households in three provinces of Central China, we calculated HDDIs and compared them according to different levels of income and dietary knowledge. A set of multivariate linear regression were further established and estimated to examine the association among family income, dietary knowledge, and household dietary diversity. RESULTS: Although the calculation formulas are different, the distributions of the five diversity indices, namely, DDS, EI, SEI, HI, and SI are similar. Family income and dietary knowledge were significantly and positively correlated with various HDDIs (P < 0.01) in addition to HI. Specifically, with a 1-unit (10 000 yuan [US $1545]) income increase, the DDIs respectively changed by 1.70% (DDS), 1.23% (EI), 0.92% (SEI), -0.62% (HI, reverse), and 0.45% (SI). With a 1-point dietary knowledge score increase, the DDIs changed by 0.91% (DDS), 1.33% (EI), 1.29% (SEI), -1.19% (HI, reverse), and 0.81% (SI). The interaction effect of income and dietary knowledge on HDDIs were significantly and negatively correlated with various HDDIs (P < 0.05) in addition to HI. CONCLUSIONS: The present findings indicated that with an increase in income and dietary knowledge, rural residents in China would consume more diversified foods. There was a substitution effect of family income and dietary knowledge on HDDIs; that is, with an increase in family income, the effect of dietary knowledge on HDDIs would decrease. The findings of this study contributed to a better understanding of issues related to the dietary diversity of rural residents in China in the context of rising income and residents' increasing dietary knowledge.