Magnesium content of dietary supplements and its association with formulation type and price

Objective: The aim of this study was to assess nutritional value of magnesium (Mg) supplements sold in Korea and to evaluate the Mg content according to formulation type and price. Materials and methods: We collected information on prices, daily nutrient content, and nutrient percentage relative to the nutrient reference values (NRVs) of 519 Mg supplements sold online and offline. These supplements were classified by formulation type (capsule, n = 64; powder, n = 24; tablet, n = 409; liquid or mixed, n = 22) and daily price (< Q1 group, Q1 - Q3 group, >_ Q3 group), and then nutritional value assessments were performed. Results: The mean Mg content in the supplements was 173.62 mg per daily dose (median value 150 mg, interquartile range 100 - 250 mg). This corresponded to 56.70% of the NRV (310 mg, the estimated average requirement of Mg). There was no significant difference in Mg content according to formulation type. As a result of comparing the Mg content among the groups according to the price of the daily dose, the < Q1 group supplements contained 205.93 mg of Mg (64.64% of the NRV) per daily dose, which was the highest among the 3 groups (p < 0.001). The Q1 - Q3 group supplements contained 167.13 mg of Mg (52.49% of the NRV) per daily dose, and the >_ Q3 group supplements contained 154.25 mg (57.46% of the NRV). Conclusion: This study may serve as a reference to consumers when purchasing Mg supplements, providing information on the formulation type and price of Mg supplements.