When Elena entered the supplement store, she expected choosing magnesium to be simple. Instead, she found shelves filled with bottles labeled magnesium malate, taurate, chloride, and oxide. Each product seemed to promise a different benefit, and the descriptions made some forms sound almost perfect. Magnesium malate was associated with normal muscle function and energy metabolism, while magnesium taurate was often marketed for cardiovascular and nervous-system support.

Elena quickly realized that marketing claims did not necessarily mean the same results for everyone. She picked up another bottle and read about magnesium chloride, which could be reasonably well absorbed but might cause digestive discomfort. Then she noticed magnesium oxide, an inexpensive and common option that was absorbed less efficiently than several other forms. As Elena compared the labels, she began wondering whether she had been focusing on the wrong question. Maybe the most important issue was not which bottle sounded best, but exactly how much magnesium each product actually contained…