Alpha-GPC (Alpha-glycerophosphocholine or sometimes just glycerophosphocholine) is a choline-containing supplement that, although found in a variety of food products that are also rich in choline, appears to be pharmacologically active at higher doses.
Alpha-GPC is mostly marketed due to it conferring dietary choline to the body following oral ingestion, and being the most efficient choline prodrug at doing so (able to influence both systemic and brain concentrations of choline). Due to the provision of the other half of the alpha-GPC molecule (glycerophosphate), alpha-GPC also appears to support the structure of cellular membranes, which is not a common mechanism attributed to choline prodrugs (only CDP-choline is associated with lipid membranes in this sense).
Oral supplementation of alpha-GPC is of interest for nootropic purposes, as it appears to have cognitive-enhancing properties (no human evidence exists to support this in otherwise-healthy youth, but it does have support in rodents) and attenuate the rate of cognitive decline in the elderly. In regards to reducing the rate of cognitive decline, alpha-GPC at high doses (1,200 mg) does appear to be somewhat effective in mild to moderate Alzheimer's disease and works nicely with the standard therapy (acetylcholinesterase inhibitors).
Athletes are at times interested in alpha-GPC due to its ability to enhance growth hormone production (of which only acute spikes have been reported so far, so it may fall to the same problems that arginine has on growth hormone) and to enhance power output, which has a lone pilot study in support of 600 mg alpha-GPC prior to exercise. Although ergogenic properties of alpha-GPC cannot be ruled out and look promising, it requires more evidence.
