Dietary staple type, protein quality and child wasting and stunting across 127 LMICs : an ecological cross-sectional study

Background Child stunting and wasting affect millions globally, with unexplained heterogeneity across LMICs. Staple foods - rice, wheat, maize, sorghum, millet and cassava - differ in protein quality (DIAAS) and zinc bioavailability. We hypothesised that these differences explain heterogeneity in undernutrition prevalence. Methods This ecological cross-sectional analysis included 127 LMICs (wasting) and 126 LMICs (stunting) using JME 2025 anthropometric data, GBD 2023 estimates and FAOSTAT 2019-2023 five-year mean food balances. Each staple was analysed individually using robust MM-estimation (primary) and quantile regression (secondary), with fixed covariates selected after circularity, correlation and multicollinearity assessment. Five sensitivity analyses tested robustness. Two secondary cross-reference analyses - WHZ, MUAC and oedema across 46 nationally representative surveys and undernutrition in infants under 6 months across 56 DHS datasets - were cross-referenced with dominant dietary staple supply. A post-hoc cross-reference analysis examined maternal short stature and low BMI by dominant dietary staple using DHS data. Findings Sorghum (beta=0.361, p<0.001) and rice (beta=0.086, p=0.004) were positively associated with wasting while Maize was negatively associated (beta=-0.139, p=0.004). Cassava showed a positive, borderline association with stunting (beta=0.975, p=0.092). HIV showed a negative wasting association reversing on exclusion of high-HIV countries. Secondary analyses confirmed MUAC-predominant wasting in cassava- and maize-dominant countries and WHZ-predominant wasting in sorghum- and millet-dominant countries. Interpretation The above findings are consistent with staple-specific growth phenotypes. Currently DHS and MICS surveys collect height and weight only - incorporating MUAC and individual staple dietary data appears imperative. Preventive measures may differ by staple context. Funding No funding was received.