Magnesium is a critical mineral involved in over 300 essential enzymatic reactions, from energy production to DNA synthesisPMID:26166051. With many individuals failing to meet recommended daily intakes, supplementation has become popular. Magnesium bisglycinate, a form chelated (bound) to the amino acid glycine, is marketed as a superior option due to enhanced bioavailability and gentler gastrointestinal effects. However, a deep dive into the scientific literature reveals a more nuanced picture, where its primary advantage may lie more in tolerability than in a dramatic absorption superiority for everyone. ### Key Findings * **The Absorption Theory:** Magnesium bisglycinate is theorized to be absorbed via amino acid transporters in the intestine, not just mineral ion channels. This dual-pathway absorption could increase uptake and, by avoiding a high concentration of free magnesium ions in the gut, reduce the osmotic effect that causes diarrhea with other forms like magnesium oxide. * **Mixed Bioavailability Evidence:** The data on superior absorption is inconsistent. One *in vitro* study using human intestinal cells found that magnesium bisglycinate showed better absorption over time compared to a sucrosomial formPMID:32098378. However, a randomized trial in 40 healthy adults found that magnesium bisglycinate did *not* significantly increase plasma magnesium levels, while magnesium oxide and citrate didPMID:39770988. Another small trial in 12 patients with impaired absorption found bisglycinate was only superior in the most compromised individualsPMID:7815675. * **Stronger Evidence for Tolerability:** The most consistent benefit reported for magnesium bisglycinate is its gentleness on the digestive system. A clinical case report noted that switching to a bisglycinate-containing formula resolved gastrointestinal side effects and improved adherence to therapyPMID:37375733. The trial in patients with ileal resection also found it was better tolerated than magnesium oxidePMID:7815675. * **Supports Muscle and Nerve Function:** *In vitro* evidence demonstrates that magnesium bisglycinate can promote the relaxation of uterine muscle cellsPMID:32098378. Another lab study found that a combination including buffered magnesium bisglycinate helped muscle cells control hypercontraction and supported mitochondrial activity after simulated strenuous exercisePMID:34765517. The resolution of neurological symptoms like headaches and paresthesia in a case study further supports its role in nervous system healthPMID:37375733. ### The Longevity Context Magnesium's importance in longevity extends far beyond simple muscle relaxation. It is a cornerstone of cellular maintenance and metabolic health. As a crucial cofactor for hundreds of enzymes, it underpins fundamental processes like ATP synthesis (cellular energy), DNA repair, and protein productionPMID:26166051. Magnesium deficiency can accelerate aging by impairing these core functions. Furthermore, magnesium is vital for bone health, not only as a structural component but also because it's required for the activation of Vitamin D, which is essential for calcium absorption and metabolismPMID:37351415. By helping to maintain bone mineral density and acting as a natural calcium antagonist to modulate inflammation, adequate magnesium intake is a key strategy for mitigating age-related decline in skeletal integrity and systemic inflammation. ### Actionable Protocol 1. **Primary Use Case:** Consider magnesium bisglycinate if you experience gastrointestinal issues (diarrhea, stomach upset) with other forms like magnesium oxide or citrate. Its primary strength appears to be superior tolerability. 2. **Dosage and Timing:** A typical supplemental dose is 200-400 mg of **elemental** magnesium per day. Taking it 1-2 hours before bed may promote relaxation and improve sleep quality due to the effects of both magnesium and glycine. 3. **Enhance Absorption:** Regardless of the form, magnesium bioavailability can be improved by taking it with a meal. The slower gastrointestinal transit time appears to increase absorptionPMID:11756061. 4. **Assessing Status:** Do not rely solely on serum magnesium tests to determine your status, as they reflect less than 1% of total body magnesium and may not detect a chronic, low-grade deficiencyPMID:38366015. Instead, track symptoms such as muscle cramps, sleep quality, anxiety levels, and exercise recovery.