Phosphatidylserine

Phosphatidylserine is a phospholipid claimed to support neuronal membrane function. Supplements can be made from several sources [6].

The largest trial is old and used PS extracted from cow brain (BC-PS). In a six-month double-blind study of 494 patients aged 65 to 93 with moderate to severe cognitive decline, 300 mg a day improved behaviour and memory compared with placebo [1]. Soybean-derived PS was developed as an alternative to bovine PS [3], and the evidence for it is smaller:

• In 78 older Japanese adults with memory complaints, soy PS did not beat placebo overall, but people with lower baseline scores improved in delayed verbal recall [2].
• In a pilot study of older adults with memory complaints, soy PS improved memory, executive function and mental flexibility [3].
• In 190 older Chinese adults with mild cognitive impairment, a supplement containing PS improved short-term memory. The supplement also contained other ingredients [7].

In children with ADHD, a randomised trial reported better ADHD scores and short-term auditory memory [8].

How oral PS works is not settled. It is claimed to enhance neuronal membrane function [6]. The clearer physiological signal is on the stress axis. In nine healthy men, 800 mg a day of bovine PS for 10 days blunted the ACTH and cortisol rise from exercise [4]. In chronically stressed men, a soy PS and phosphatidic acid complex normalised the ACTH and cortisol response to a laboratory stress test, but only at the higher dose and only in the most stressed subjects [5].

Soy PS was safe in older adults at up to 600 mg a day for 12 weeks, with no differences from placebo in blood tests, blood pressure, heart rate or adverse events [6]. The bovine-PS trial also found it well tolerated [1]. An unexpected finding in one pilot study was a fall in blood pressure [3].