Prevalence and non-invasive predictive models of vitamin D insufficiency in Paraguayan youth: the role of body composition and traditional mate consumption.

BACKGROUND: Vitamin D (VD) insufficiency among youth remains a latent public health concern in Paraguay, and non-invasive, population-specific screening tools are unestablished. This study aimed to identify clinical, body composition, and lifestyle predictors to develop a preliminary, non-invasive risk scoring system for Paraguayan youth. METHODS: Serum 25-hydroxyvitamin D levels, bioelectrical impedance-derived body composition, and lifestyle habits were evaluated in 164 participants (aged 17-35 years) at the Universidad Santa Clara de Asís. Multivariable logistic regression models were constructed after resolving multicollinearity (variance inflation factor <1.40) and underwent internal validation via 1,000 bootstrap resamples. RESULTS: The overall prevalence of VD insufficiency (<30 ng/mL) was 48.2%. Multivariable analysis revealed an independent contribution of sex-specific muscle mass deviations (Δ Muscle Mass), showing decreased VD levels in both the sarcopenic obesity phenotype and high muscle-low fat athletic phenotype, supporting the skeletal muscle tissue reservoir hypothesis. Among lifestyle factors, full-coverage clothing was an independent risk factor, whereas vigorous physical activity and habitual mate/tereré consumption (≥4 days/week) were significant associated with a lower probability of VD insufficiency. The global predictive scorecard achieved an optimism-corrected area under the receiver operating characteristic curve (optimism-corrected AUC) of 0.714. Crucially, the subgroup model restricted to overweight individuals (BMI ≥ 25 kg/m2) demonstrated acceptable exploratory discrimination (optimism-corrected AUC = 0.768, sensitivity 69.2%, specificity 89.7%), serving as a preliminary proof-of-concept assessment for risk stratification. CONCLUSION: By integrating body composition dynamics and cultural habits, this cost-effective model provides a preliminary, exploratory non-invasive screening structure for Paraguayan youth that warrants further multi-center prospective validation before clinical implementation.