What is phosphatidylserine? A plain-English guide

Phosphatidylserine, or PS for short, is a phospholipid [1]. A phospholipid is a type of fat that helps build the thin wrapper around each cell. In nerve tissue, PS is concentrated on the inner side of that wrapper [1].

PS is sold as a supplement you swallow [2]. Early studies used PS taken from cow brain [2][8]. A 2006 review says soy PS is the preferred form [2]. That is because of the possible risk of prion infection, an infection that can pass on through eating contaminated brain tissue [2].

In 2004, FDA said soy PS and cow-brain PS may not be the same substance, because the fats they carry differ [9].

Scientists think that in nerve cells, PS helps control how brain chemicals are released and how some signal sites work [1]. That is theory, not proof that a supplement does anything.

PS supplements are sold for memory and thinking [2]. A 2006 review says most research had focused on people with some loss of thinking skills [2].

Researchers have also tested PS for feelings of stress and for exercise [5][6][7].

Each trial below compared PS with a placebo. Some were randomized controlled trials, where people are split into groups by chance. As of November 11, 2026, we found no meta-analysis of PS for memory in adults without a diagnosed condition (PubMed and Europe PMC searches). A meta-analysis pools the results of many trials on one question.

Does phosphatidylserine help memory?

Evidence grade for memory: C, limited. Why this grade

Evidence is mixed, and the answer depends on the form of PS. In a 12-week trial of 149 adults with age-related memory problems, cow-brain PS was compared with a placebo [3]. The PS group took 100 mg three times a day [3]. They did better than the placebo group on tests based on everyday learning and memory tasks [3]. An analysis of subgroups suggested that people who scored lower at the start were the most likely to respond [3].

Results for soy PS look different. In a 12-week trial, 120 adults over 57 with memory problems took soy PS or a placebo [4]. The soy PS groups took 300 or 600 mg a day [4]. Neither dose showed a clear difference from the placebo on memory, reaction time, planning or attention [4].

FDA said there is considerable uncertainty in applying results from cow-brain PS to soy PS, or the other way around [9]. FDA also said flaws in how the studies it reviewed were designed and analyzed limit how far they can be trusted [9]. These trials were all in older adults with memory problems, so results may not apply to healthy adults [3][4].

Does phosphatidylserine help with stress?

Evidence grade for perceived stress: C, limited. Why this grade

Evidence is mixed. In young adults, 300 mg of PS a day for a month was associated with feeling less stressed and in a better mood [5]. But this was seen only in people with higher scores for neuroticism [5]. Neuroticism is a personality trait marked by a tendency to feel worry and strain.

A later trial was funded by the companies Lipogen and Lonza [6]. In this double-blind trial, 75 healthy men took a soy mix of PS and a related fat, or a placebo, for 42 days [6]. The mix made no clear difference to how stressed the men felt during a lab stress test [6].

Does phosphatidylserine help exercise?

Evidence grade for endurance performance: C, limited. Why this grade

One small trial reports a benefit. Fourteen active men did a hard, stop-start cycling test before and after 10 days of 750 mg a day of soy PS or a placebo [7]. With PS, the time they could keep going in the final, hardest stage rose from 7 minutes 51 seconds to 9 minutes 51 seconds [7]. With the placebo, it stayed about the same [7]. PS made no clear difference to how the men felt during the test [7].

The authors called it the first study to report better exercise capacity after PS [7]. As of November 11, 2026, we found no trial from another research group that repeated this result (PubMed and Europe PMC searches).

To see what each grade on this page means, read how we grade evidence.

Table: Doses used in studies (not a recommendation)

These are amounts used in research, not advice. Health Canada's guide for companies that apply to sell PS products lists 300 mg of PS a day for adults 18 and older [10]. Talk to a clinician before using any supplement.

In a 12-week trial, 120 older adults took 300 or 600 mg of soy PS a day, or a placebo [8]. Blood tests, blood pressure, heart rate and side effects showed no clear difference between the groups [8].

Health Canada's guide for PS products does not require any caution, warning or side-effect statement on the label [10].

As of November 11, 2026, the sources we checked do not include any study in people of how PS interacts with medicines (PubMed search). If you take any medicines, talk to your doctor or pharmacist before combining them with phosphatidylserine.

As of November 11, 2026, the sources we checked do not name any groups who should be careful (PubMed safety search and Health Canada monograph). They do not name pregnancy or breastfeeding either. That does not show that PS is safe for these groups.

Ask a clinician before use if you are pregnant, breastfeeding, taking medicines or managing a health condition.