Phosphatidic acid (PA) is a naturally occurring phospholipid, a type of fat molecule found in all cell membranes. It is also present in certain foods, such as cabbage, radish leaves, and soy products. PA has gained attention in sports nutrition due to its potential to act as a signaling messenger that promotes muscle growth. Now sold as a dietary supplement, PA is positioned as a non-hormonal aid for individuals seeking to maximize gains from resistance training.
Cellular Role and Signaling
The theoretical basis for phosphatidic acid supplementation centers on its function as a lipid messenger that directly influences the cellular processes governing muscle growth. Within the muscle cell membrane, PA plays a structural role but also operates as a specific signaling molecule. It is produced by an enzyme called phospholipase D (PLD), which is activated in response to mechanical stress, such as the tension generated during a weightlifting exercise.
The most significant aspect of PA’s signaling function is its involvement with the mechanistic Target of Rapamycin (mTOR) pathway, the master regulator of muscle protein synthesis (MPS). Research suggests that PA can directly interact with the mTOR protein, enhancing the activity of the mTOR complex 1 (mTORC1). This action essentially turns up the cellular signal to build new muscle tissue.
This activation provides a nutrient-independent mechanism for stimulating muscle growth, complementing the pathways activated by amino acids and growth factors. By acting as a structural lipid and an activator of mTOR, PA amplifies the anabolic response to resistance exercise. Some studies also suggest that supplemental PA may be metabolized into lysophosphatidic acid, which then activates mTORC1 indirectly through the ERK signaling pathway.
Analyzing the Research Evidence
Human clinical trials have attempted to confirm the muscle-building theory behind phosphatidic acid, yielding a mix of both promising and conflicting results. Studies that have shown positive outcomes typically involve resistance-trained men supplementing with 750 milligrams of PA daily for eight weeks while following a structured training program. In one notable trial, subjects consuming PA saw a significant increase in lean body mass, gaining an average of 2.4 kilograms more than the placebo group over the study period.
This same trial also reported substantial strength gains in the PA group, including a significant increase in the leg press one-repetition maximum (1-RM) compared to the placebo group. Another study similarly found that PA supplementation led to greater increases in squat strength and lean body mass. These results suggest that PA may provide an ergogenic benefit when combined with consistent weight training.
However, not all research supports these findings, as other well-controlled studies have reported null or mixed results. Some trials, even when using the standard 750 mg dose, found no statistically significant difference between the PA and placebo groups in terms of increases in lean mass or muscle strength. These conflicting outcomes may be partially explained by methodological differences between the studies, such as variations in the training program intensity, the source of the PA, or the use of different measurement techniques for body composition.
Studies using a lower training volume or different PA doses, such as 250 mg or 375 mg, have generally failed to show an effect over a placebo. While PA holds promise due to its mechanistic link to mTOR, its efficacy as a performance-enhancing supplement is still considered controversial and dependent on consistent use at a specific dose. Furthermore, positive findings often involve highly trained individuals, indicating the supplement may offer a marginal advantage to those already maximizing their training potential.
Recommended Intake and Safety Profile
Recommended intake is largely guided by the doses used in successful clinical trials. The most commonly studied and effective intake level is 750 milligrams of PA consumed once daily. This dose is typically taken 30 to 60 minutes before a workout on training days to maximize availability during mechanical stress. On non-training days, the supplement can be taken at any convenient time, usually in the morning.
Phosphatidic acid is primarily derived from lecithin, which is sourced from either soy or sunflower. The soy-derived form, often branded as Mediator PA, has been the specific type used in several positive human trials. Some cellular research suggests that soy-PA may be more effective at stimulating mTOR signaling than other sources. Supplementation should be maintained consistently for at least eight weeks to align with the duration of the studies that reported beneficial changes in body composition and strength.
Regarding safety, phosphatidic acid is generally recognized as safe (GRAS). Clinical trials investigating PA supplementation have consistently reported that it is well-tolerated by healthy, resistance-trained individuals. The literature does not indicate any major adverse side effects associated with the standard 750 mg daily dose used over the typical eight-week study period. Minor gastrointestinal discomfort has been reported rarely, but PA is considered a low-risk compound for muscle-building support.