Phosphatidylserine (PS) is a phospholipid component found in cell membranes, particularly abundant in neural tissue. Its use to support the "Cortisol body system" refers to claims that it may help modulate the body's physiological response to stress, specifically by influencing cortisol levels. The scientific validation primarily comes from small human studies and some animal research. For example, a few clinical trials have shown that supplementation with phosphatidylserine (typically 300-800 mg daily) can attenuate the rise in cortisol levels induced by acute physical or mental stress. Notable studies include a randomized controlled trial by Monteleone et al. (1992), which found PS supplementation blunted ACTH and cortisol responses to exercise in healthy men. Another study by Fahey et al. (1998) found that PS reduced cortisol response following intense cycling in male athletes. However, other studies have found no significant effect, and most trials have small sample sizes and short durations.

While there is a plausible mechanism—PS may affect the hypothalamic-pituitary-adrenal (HPA) axis—evidence is not robust enough for unequivocal clinical recommendations. Therefore, while the use of phosphatidylserine for supporting healthy cortisol levels has some scientific support, it remains moderate in strength and further research is needed.