Also known as: PA, Soy-derived phosphatidic acid, Mediator, Egg-derived PA
Muscle & RecoveryEmerging evidence
A phospholipid that activates the same signalling pathway resistance training does. One of very few supplements with a direct muscle-building mechanism, and results that have not lived up to it.
Typical dose
750.0–750.0 mg per day
Around training, split if dosing twice
What it is
Phosphatidic acid is a phospholipid, a fat molecule that forms part of cell membranes and also acts as a signalling molecule inside cells.
Supplements derive it mostly from soy lecithin, with egg-derived versions also available. Source matters more here than for most phospholipids, because the fatty acids attached to the backbone differ, and some research suggests that affects activity.
It is worth distinguishing from phosphatidylserine, which is a different phospholipid used for cortisol and cognition. The names are similar and the uses are unrelated.
How it works
Phosphatidic acid binds and activates mTOR, the central regulator of muscle protein synthesis. That is the same pathway mechanical loading activates during resistance training, and the same one leucine feeds into.
This is unusually direct for a supplement. Rather than supplying substrate or influencing hormones, it acts on the signalling switch itself, which is why it attracted serious interest.
The problem is delivery. Whether oral phosphatidic acid survives digestion intact and reaches muscle cells in quantities that meaningfully affect mTOR is the unresolved question, and it is the likely explanation for the gap between mechanism and results.
What the evidence shows
Early trials in resistance-trained individuals reported greater gains in lean mass and strength with 750 mg daily alongside training, which generated considerable interest.
Subsequent work has been less consistent, with several trials finding no meaningful difference from placebo. Reviews have generally concluded the evidence is mixed and insufficient to recommend it confidently.
That pattern of a promising early finding not replicating is common in this field. The mechanism remains genuinely interesting, but a supplement is judged on outcomes rather than on how good its mechanism looks on paper.
Dosing
The dose used across essentially all the research is 750 mg daily, often split around training.
Check the actual phosphatidic acid content. Many products list a soy lecithin extract at a higher milligram figure while supplying considerably less actual PA, which is one of the more common ways this ingredient is underdosed.
Taken alongside adequate protein and training, since it acts on a pathway that needs both to matter. As a standalone with inadequate protein it has nothing to amplify.
At a glance
Common forms
Soy-derived phosphatidic acid, Egg-derived phosphatidic acid, Within muscle-building formulas
Half-life / duration
Effects assessed over 8-12 week training studies
Timing
Around training, split if dosing twice
Competition status
Permitted — not on the WADA Prohibited List
Category
Muscle & Recovery
Safety and side effects
Phosphatidic acid has been well tolerated in the trials conducted, with few adverse effects reported beyond occasional digestive upset.
Long-term data beyond the trial durations is limited. Because mTOR is involved in cell growth generally, anyone under medical care should check before use rather than assume a muscle supplement is neutral.
Who should avoid it
Soy-derived products require soy allergen declaration. Speak to your doctor before use if you are under medical care or take regular medication. Long-term data is limited. Not established in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
