Phosphatidylserine (PS) is a major lipid of mammalian cell membranes,[1] comprising 15% of the total phospholipids in the human brain.[2] It was originally extracted from the brains of cattle in the 1990s[3] but has since been derived from soy due to safety concerns in regards to Mad Cow Disease.[4][2] PS is sometimes studied alongside the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), since PS is attached to DHA molecules in the brain.[2]