Serum vs. Dietary Magnesium and Cardiometabolic Outcomes in Saudi Adolescents

Background/Objectives: Magnesium (Mg) is an essential micronutrient that participates in more than 300 enzymatic reactions, with well-established functions in glucose and lipid metabolism and cardiovascular health. Although serum Mg is routinely used in clinical practice, circulating concentrations may not accurately represent total body Mg status because of tight physiological regulation. The present study evaluated the associations of serum Mg concentration and dietary Mg intake with cardiometabolic outcomes in a cohort of Saudi adolescents. Methods: This cross-sectional study involved 234 Saudi adolescents (166 girls, 68 boys; mean age 14.8 ± 1.7 years) who were assessed for anthropometrics, biochemical parameters and dietary intake. Hypomagnesemia was classified as serum Mg <0.75 mmol/L, while inadequate dietary Mg intake was based on age- and sex-specific cutoffs for children. Results: Hypomagnesemia was present in 87 participants (37.2%) and was more common among boys than girls (50% vs. 31.9%, p = 0.011). No significant differences in the assessed cardiometabolic measurements were observed across serum Mg tertiles. Absolute dietary Mg intake was strongly correlated with total energy and other dietary intakes and was inversely associated with body mass index. Associations based on absolute dietary Mg intake were attenuated after energy adjustment for overweight/obesity. For elevated triglycerides, the highest vs. lowest tertile of residual-adjusted Mg showed a nominal inverse association in the age- and sex-adjusted model (OR: 0.40; 95% CI: 0.17-0.96). However, the corresponding trend did not remain statistically significant after false discovery rate correction. Conclusions: Serum Mg showed limited associations with cardiometabolic outcomes, while associations between dietary Mg and cardiometabolic outcomes were sensitive to energy adjustment and multiple-comparison correction. The inverse association between residual-adjusted Mg and elevated triglycerides should therefore be considered exploratory. These findings highlight potential differences between serum and dietary Mg as indicators of Mg status and underscore the importance of accounting for total energy intake when examining dietary Mg in relation to cardiometabolic health in adolescents.