Phosphatidylserine is the major phospholipid in the brain and is embedded in cell membranes. Along with other phospholipids, it makes up the basic structural components of the membrane. It is usually kept on the inner-leaflet (the cytosolic side) of cell membranes by an enzyme called flippase.
PS can be found in meat, but is most abundant in the brain and in offal such as liver and kidney. Only small amounts of PS can be found in dairy products or in vegetables, with the exception of white beans. Phosphatidylserine extracted from soya beans is called Soy-PS.
After ingestion phosphatidylserine is hydrolyzed to lysophosphatidylserine which is absorbed in the small intestine. The average daily intake of PS from the diet in western countries is estimated to be about 130mg a day. The total amount of phosphatidylserine in the body is about 60 grams, 30 grams of which is within cell membranes of the brain.