Milk-based phospholipids increase morning cortisol availability and improve memory in chronically stressed men

Abstract

Phospholipids (PLs) have been shown to dampen the activity and reactivity of the hypothalamic-pituitary-adrenal axis (HPAA). To further investigate stress protective effects of PL, 75 chronically stressed men aged 30 to 51 years were enrolled in a randomized and placebo-controlled trial. The subjects received a bovine milk drink with either 0.5% PL, 1% PL, or a placebo for 42 days to test the hypothesis that supplementation with specific phospholipids would normalize the cortisol response of the HPAA. For determining HPAA activity, the cortisol awakening response was studied before and after treatment. In addition, participants were exposed to an acute stressor, the Trier Social Stress Test, to assess treatment effects on stress reactivity and stress-related memory impairment. After receiving PL-enriched milk, both PL groups showed a delayed decline from peak levels in morning salivary cortisol, suggesting a prolonged availability of free cortisol. Treatment with 0.5% PL additionally resulted in a stronger increase of cortisol after awakening, whereas no such differences could be observed in the 1% PL group and the placebo group, respectively. The acute stress response did not significantly differ among placebo and PL groups. An exploratory data analysis further revealed that elderly participants receiving the higher PL dosage had a significant better memory performance after the Trier Social Stress Test as compared with elderly participants from the placebo and low-PL dosage group; no such difference was observed at baseline. Our results suggest that PL may increase the availability of cortisol in chronically stressed men and may attenuate stress-induced memory impairments. Results of the present study are discussed within the context of previous research and current state of knowledge.