Frontiers in Nutrition · Jul 15, 2026

Planetary health diet index and low muscle mass in adults aged 20-60 years: exploratory evaluation of a dairy-upweighted outcome-specific adaptation

By He JJ, Chen XL, Ning C et al.

BACKGROUND: Increasing evidence indicates that the Planetary Health Diet Index (PHDI), proposed within the EAT-Lancet framework, not only supports environmental sustainability but also contributes to the prevention of various diseases. However, the rigorous restriction of animal-sourced proteins in the standard PHDI may overlook the heightened anabolic needs of aging populations. This study primarily aimed to evaluate the association between PHDI-US adherence and low muscle mass (LMM) and to compare this association with other commonly used dietary indices. As a secondary exploratory step, we examined whether an exploratory dairy-upweighted score, derived by multiplying the original PHDI-US total score by the observed dairy intake amount, might show a stronger association with LMM. METHODS: Multivariable logistic regression and restricted cubic spline (RCS) models were used to evaluate the association between the Planetary Health Diet Index for the United States (PHDI-US) and low muscle mass (LMM). Random-forest feature-importance analysis was then used to identify the most influential dietary component within the PHDI-US and to derive a dairy-upweighted version of the score (PHDI-Dairy). We then examined the association between dairy intake and LMM in an independent Southern Chinese cohort. RESULTS: In fully adjusted models, higher PHDI-US and Alternative Healthy Eating Index scores were associated with lower odds of LMM, whereas a higher Dietary Inflammatory Index score was associated with higher odds of LMM. Healthy Eating Index and Mediterranean Diet Index scores were not statistically significant in fully adjusted quartile analyses. In exploratory analyses, a dairy-upweighted score (PHDI-Dairy) showed a stronger inverse association with LMM than the original PHDI-US. In a separate hospital-based Southern Chinese cohort, higher dairy intake was associated with lower odds of LMM, providing supportive evidence for the dairy-related finding. CONCLUSION: PHDI-US was modestly associated with lower odds of LMM, and the exploratory dairy-upweighted score, PHDI-Dairy, showed a stronger inverse association with LMM.

doi.org/10.3389/fnut.2026.1782327Open accessPubMed 42528766Populations