Quick Comparison
| Alpha-GPC | Citicoline (CDP-Choline) | |
|---|---|---|
| Half-Life | 4-6 hours | 56-71 hours (sustained release characteristics) |
| Typical Dosage | Standard: 300-600 mg daily in 1-2 doses. For racetam stacking: 300 mg per racetam dose. Clinical (Alzheimer's): 1200 mg daily in 3 divided doses. | Standard: 250-500 mg daily. Clinical studies use 500-2000 mg daily. Take in the morning — mildly stimulating. Cognizin is the most studied form. Can be split into 2 doses. Often combined with racetams to provide the choline needed for enhanced acetylcholine turnover. |
| Administration | Oral (capsules, powder). High oral bioavailability. | Oral (capsules, powder). Cognizin branded form is most studied. Take in the morning. |
| Research Papers | 10 papers | 10 papers |
| Categories |
Mechanism of Action
Alpha-GPC
Alpha-GPC (L-alpha-glycerylphosphorylcholine) is hydrolyzed by phospholipases in the gut and brain to release free choline, which is transported across the blood-brain barrier via the choline transporter (CHT1) and taken up by neurons for acetylcholine synthesis via choline acetyltransferase (ChAT). It is the most efficient oral choline source for raising brain acetylcholine levels due to high bioavailability and direct utilization. Alpha-GPC also provides glycerophosphate (glycerol-3-phosphate), which enters the Kennedy pathway and supports phosphatidylcholine and cell membrane phospholipid synthesis. It may stimulate growth hormone release through cholinergic activation of the pituitary. Alpha-GPC enhances high-affinity choline uptake and supports muscarinic (M1, M2) and nicotinic receptor function.
Citicoline (CDP-Choline)
Citicoline (CDP-choline) is hydrolyzed in the gut by alkaline phosphatase to choline and cytidine-5'-monophosphate, which are absorbed separately and reassembled in the brain via the Kennedy pathway. Choline feeds two critical pathways: (1) Acetylcholine synthesis via choline acetyltransferase (ChAT) — the primary memory and learning neurotransmitter acting at muscarinic and nicotinic receptors. (2) Phosphatidylcholine synthesis via CTP:phosphocholine cytidylyltransferase — the structural component of neuronal membranes and synaptic vesicles. Cytidine is dephosphorylated to uridine, converted to UTP, and supports RNA synthesis and CDP-choline formation for synapse formation. Citicoline also activates SIRT1 (possibly via NAD+ modulation) and increases brain norepinephrine and dopamine (mechanism unclear — may enhance synthesis or release). It is the only choline source providing both cholinergic and membrane-building support in one molecule.
Risks & Safety
Alpha-GPC
Common
Headache, heartburn, dizziness, skin rash.
Serious
High chronic doses may be associated with increased stroke risk (epidemiological data, not confirmed causally).
Rare
Fishy body odor from trimethylamine production, depression.
Citicoline (CDP-Choline)
Common
Headache (especially with racetams — indicates too much cholinergic stimulation), nausea, diarrhea.
Serious
None documented at standard doses.
Rare
Insomnia, blurred vision.
Full Profiles
Alpha-GPC →
The most bioavailable choline source for the brain. Alpha-GPC crosses the blood-brain barrier efficiently and directly provides choline for acetylcholine synthesis. Used clinically in Europe for Alzheimer's disease and cognitive decline. The go-to choline supplement for stacking with racetams and preventing the headaches that come from increased acetylcholine demand.
Citicoline (CDP-Choline) →
A naturally occurring intermediate in the synthesis of phosphatidylcholine, the primary phospholipid in neuronal cell membranes. Citicoline provides both choline (for acetylcholine and phospholipid synthesis) and cytidine (converted to uridine, supporting RNA and synapse formation). It is prescribed in Europe and Japan for stroke recovery and cognitive decline. Cognizin is the most studied branded form.