Adherence to Chinese Dietary Guidelines Is Associated with Better Bone Status in School-Aged Children and Adolescents

Background/Objectives: Diet plays a crucial role in bone health; however, most studies have focused on individual nutrients or foods. The relationship between overall dietary quality and bone health in children and adolescents remains unclear. This study aimed to assess the association between diet quality scores and bone health in a pediatric population. Methods: A total of 3299 students aged 9–17 participated in this study. Dietary quality was assessed using the Chinese dietary guidelines index for Children and Adolescents (CDGI-Cs). Bone health was evaluated through calcaneal quantitative ultrasound (QUS), utilizing the speed of sound (SOS) as the key indicator. Generalized linear models and binary logistic models were used to analyze the association between CDGI-C scores and bone health outcomes (SOS Z scores and the risk of low SOS), respectively. Results: After full adjustment, CDGI-C scores showed a significant positive association with SOS. A 10-point increase in CDGI-C scores was associated with a 0.08-unit increase in SOS Z score (95% CI: 0.04, 0.11) and a 15% reduction in the risk of low SOS (OR = 0.85, 95% CI: 0.76, 0.94). Compared to participants in the lowest quartile of CDGI-C scores, those in the highest quartile exhibited significantly higher SOS Z scores (β = 0.18, 95% CI: 0.08, 0.29, p for trend < 0.001), and a 29% lower risk of low SOS (OR = 0.71, 95% CI: 0.50, 1.00, p for trend = 0.050). In dietary item analysis, higher intake of dairy and dairy products (β = 0.02, 95% CI: 0.00, 0.03) and seafood (β = 0.01, 95% CI: 0.00, 0.03) remained positively associated with SOS Z scores. Conclusions: Higher diet quality, as measured by CDGI-C, was significantly associated with better bone health in children and adolescents. Dairy, dairy products, and seafood emerged as key dietary components contributing to this positive association.