Quick Comparison
| ALCAR | Magnesium Glycinate | |
|---|---|---|
| Half-Life | 4-5 hours | 12-17 hours |
| Typical Dosage | Standard: 500-2000 mg daily in 1-2 doses. For cognitive support: 1000-2000 mg daily. For neuropathy: 1500-3000 mg daily. Take in the morning — may be mildly stimulating. | Standard: 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. |
| Administration | Oral (capsules, powder). Well-absorbed on an empty stomach. | Oral (capsules, powder, tablets). Well-tolerated. Take with or without food. |
| Research Papers | 9 papers | 8 papers |
| Categories |
Mechanism of Action
ALCAR
ALCAR crosses the blood-brain barrier via the organic cation transporter (OCTN2) more effectively than L-carnitine. In neurons, it is hydrolyzed by carnitine acetyltransferase to donate its acetyl group to coenzyme A, forming acetyl-CoA—which can then be used for acetylcholine synthesis via choline acetyltransferase, effectively providing raw material for the memory neurotransmitter. ALCAR also transports long-chain fatty acids across the inner mitochondrial membrane via the carnitine palmitoyltransferase system for beta-oxidation and ATP production. ALCAR activates nerve growth factor (NGF) signaling, possibly through modulation of NGF receptor (TrkA) expression or downstream MAPK/ERK pathways. It has antioxidant properties, reducing lipid peroxidation in mitochondrial membranes and scavenging free radicals. These mechanisms support cognitive function and neuroprotection.
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.
Risks & Safety
ALCAR
Common
Nausea, fishy body odor, restlessness, gastrointestinal discomfort.
Serious
May increase agitation in Alzheimer's patients. TMAO production may be a cardiovascular concern with chronic high doses.
Rare
Seizures in susceptible individuals, increased thyroid activity.
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.
Full Profiles
ALCAR →
Acetyl-L-Carnitine is an acetylated form of L-Carnitine that crosses the blood-brain barrier more effectively than regular L-Carnitine. In the brain, it donates its acetyl group for acetylcholine synthesis and supports mitochondrial fatty acid oxidation for energy. Used clinically for age-related cognitive decline, depression, and diabetic neuropathy.
Magnesium Glycinate →
A highly bioavailable form of magnesium chelated with glycine. The glycine component adds its own calming effects (inhibitory neurotransmitter), making this form particularly effective for anxiety, sleep, and stress. Better tolerated than magnesium citrate or oxide with fewer GI side effects. Magnesium deficiency affects an estimated 50-80% of adults and directly impairs cognitive function.