Phosphatidylserine (PS) is a phospholipid component found in cell membranes, especially in the brain. It has been studied as a potential treatment for cognitive decline and Alzheimer's Disease (AD). The rationale behind its use is based on its role in neuronal cell membrane structure and function, which are disrupted in neurodegenerative diseases like AD. Early studies, mostly from the 1980s and 1990s, used PS derived from bovine sources and demonstrated modest improvements in memory, behavior, and cognition in elderly patients with cognitive impairment, including those with AD. However, concerns over prion diseases led to a switch to plant-based (soy-derived) PS in more recent research.

The evidence for soy-derived PS is less robust. Several small randomized controlled trials have shown mild benefits on memory and attention in elderly subjects with mild cognitive impairment, but larger, well-designed studies in patients with confirmed AD are lacking. Meta-analyses and systematic reviews generally conclude that while PS is safe and may have some positive effects on cognition, the evidence is insufficient to firmly support its use as a treatment for Alzheimer's Disease. Major guidelines do not recommend PS as a standard therapy for AD. Therefore, its use is based on limited scientific evidence, with an evidence rating of 2 out of 5.