Comparing the Bioavailability of Two Seawater-Derived Magnesium Preparations

Magnesium deficiency is a common problem worldwide; however, existing magnesium dietary supplement sources require large doses to overcome low bioavailability. Previously research has established that seawater contains magnesium in addition to 72 other trace and ultratrace minerals, resulting in better bioavailability than traditional magnesium sources. The purpose of the present study was to compare the bioavailability of magnesium obtained from two different seawater processing methods (hydroxide vs. citrate). In a double-blind manner, healthy, young men and women (N = 20) completed three trials using a crossover design: placebo (maltodextrin), seawater magnesium citrate (Aquamin®-Mg; min 10% elemental magnesium), and seawater-derived magnesium hydroxide (Aquamin®-MgTg; min 33% elemental magnesium). Total magnesium doses were standardized on the Recommended Daily Allowance (RDA) for elemental magnesium. An incremental, 18-h urine magnesium excretion test was used to assess relative magnesium bioavailability. The urine uptake was verified by short-term serum magnesium measurements (1- and 2-h postingestion). Serum and urine magnesium concentration were analyzed in triplicate using a colorimetric assay. We found that both seawater-derived magnesium preparations significantly increased magnesium absorption compared with placebo (>97% change) but did not differ from each other when standardized on magnesium dose. The magnesium hydroxide form may be particularly useful since its greater magnesium content allows for ingestion of smaller total quantities compared to soluble magnesium citrate.