What it's actually good for
Alpha-GPC (alpha-glycerylphosphorylcholine) is a choline compound that efficiently crosses the blood-brain barrier, making it one of the more bioavailable forms of supplemental choline. In the brain, it serves as a precursor to acetylcholine, a neurotransmitter central to memory and learning. The strongest clinical evidence comes from trials in older adults with cognitive decline, where 1200 mg/day has shown meaningful improvements in memory and attention. In healthy younger adults, the cognitive data is thinner and less conclusive. On the athletic side, a few small RCTs have found acute improvements in peak power output and growth hormone response when Alpha-GPC is taken before resistance exercise, but these studies need replication with larger samples. It earns a B because the mechanistic rationale is strong and the available RCTs are positive, but the evidence base is still small, especially for the healthy-adult nootropic use case that drives most consumer interest.