Quick Comparison

Magnesium GlycinateNAC
Half-Life12-17 hours5.6 hours
Typical DosageStandard: 200-400 mg elemental magnesium daily (note: magnesium glycinate is ~14% elemental magnesium by weight, so 2000 mg magnesium glycinate provides ~280 mg elemental). Take in the evening for sleep benefits. Can be split into 2 doses.Standard: 600-1800 mg daily in 1-2 divided doses. Clinical (OCD/addiction): 1200-2400 mg daily. Take on an empty stomach for best absorption. Some practitioners combine with Vitamin C to enhance glutathione recycling.
AdministrationOral (capsules, powder, tablets). Well-tolerated. Take with or without food.Oral (capsules, powder). Take on an empty stomach. Unpleasant sulfur taste in powder form.
Research Papers8 papers10 papers
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Mechanism of Action

Magnesium Glycinate

Magnesium is required for over 300 enzymatic reactions including neurotransmitter synthesis (tyrosine hydroxylase, tryptophan hydroxylase), energy production (ATPases, kinases, glycolytic enzymes), and DNA repair (PARP, DNA polymerases). In the brain, magnesium blocks NMDA receptors at the voltage-dependent Mg2+ binding site within the channel pore (GluN1/GluN2 subunits), preventing excessive calcium influx and excitotoxicity — Mg2+ is displaced only upon depolarization and glycine/glutamate binding. The glycine component activates inhibitory glycine receptors (GlyR alpha1/alpha2) in the brainstem and spinal cord, and serves as an obligatory co-agonist at the GluN1 glycine site of NMDA receptors. Glycine also modulates NMDA receptor function. Together, magnesium and glycine produce calming effects through complementary inhibitory mechanisms: reduced glutamatergic excitability and enhanced inhibitory neurotransmission.

NAC

NAC is deacetylated to cysteine, the rate-limiting substrate for glutathione synthesis via gamma-glutamylcysteine synthetase and glutathione synthetase. Glutathione (GSH) is the primary intracellular antioxidant in neurons, neutralizing reactive oxygen species and maintaining redox balance. NAC also activates the cystine-glutamate antiporter (System Xc-, composed of SLC7A11 and SLC3A2 subunits), which exchanges extracellular cystine for intracellular glutamate in a 1:1 ratio. This non-vesicular mechanism modulates extrasynaptic glutamate levels, reducing NMDA receptor overactivation and excitotoxicity. The glutamate-modulating effect explains NAC's promise in OCD (reducing corticostriatal glutamate hyperactivity), addiction (normalizing nucleus accumbens glutamate after drug exposure), and neurodegenerative conditions involving glutamate dysregulation.

Risks & Safety

Magnesium Glycinate

Common

Mild drowsiness (often desired), loose stools at high doses (less than with other forms).

Serious

Avoid high doses with kidney impairment.

Rare

Diarrhea, nausea.

NAC

Common

Nausea, vomiting, diarrhea, foul-smelling breath.

Serious

May interact with blood thinners and nitroglycerin. Concern that antioxidants may reduce efficacy of chemotherapy (theoretical).

Rare

Bronchospasm (in people with asthma), anaphylactic-like reactions.

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