Phosphatidylserine (PS) is a phospholipid and a major component of cell membranes within the body. Phospholipids are fatty substances made up predominantly of fatty acids, amino acids, and the mineral phosphorous/phosphate. Phosphatidylserine is found in particularly high concentrations in the membranes of cells with high metabolic activity including those of the brain, heart, liver, and skeletal muscle.
PS therefore helps to maintain the health of cell membranes which is essential for the functioning of important chemical such as hormones, neurotransmitters, and immune signalling molecules such as cytokines. There are receptors for all of these chemicals on cell membranes; if the cell membrane is not healthy the receptors will not be either and these chemicals may not do their jobs correctly.
Dietary sources of PS are mainly limited to animal sources. Meat, organ meats, fish, and seafood having the highest concentrations. A number of beans such as soy beans also contain significant amounts but it is scare in other plant foods.
Phosphatidylserine as a supplement is best known as a a brain function enhancer. Studies using PS derived from the brains of cows found it improves cognitive function, particularly age-related memory impairment and the symptoms of Alzheimer's disease. PS may also improve other aspects of cognitive function such as concentration and mental focus. The PS available in supplement form is extracted from soy and it is uncertain whether this is as effective as that derived from cows when taken orally by humans. One study in rats however found they had comparable effects.
Another interesting effect of phosphatidylcholine is its ability to suppress production of the stress hormone cortisol. Elevated cortisol is found in depression, anxiety and other mood and stress disorders. Cortisol production can also be dysfunctional in adrenal fatigue and illnesses including chronic fatigue syndrome and fibromyalgia.
Finally PS supplementation has been found to significantly increase the length of time taken to reach exhaustion during exercise; this possibly being due to the role that it plays in ATP (energy) production.

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References:
Kingsley MI Wadsworth D Kiduff LP McEneny J Benton D (2005) Effects of phosphatidylserine on oxidative stress following intermittent running Medicine & Science in Sports & Exercise 37(8):1300-6
Sahelian R (2000) Mind Boosters St. Martin's Griffin
Hellhammer J Fries E Buss C Engert V Tuch A Rutenberg D Hellhammer D (2004) Effects of Soy Lecithin Phosphatidic Acid and Phosphatidylserine Complex (PAS) on the Endocrine and Psychological Responses to Mental Stress Stress: The International Journal on the Biology of Stress 7(2):119–26















