the probiotic interventions were associated with a statistically significant reduction in cortisol levels, a key biomarker of physiological stress (SMD = -0.26, 95% confidence interval [CI] [-0.45, -0.08], p = 0.005).
The 14-day supplementation period that coincided with typical night-day sleep-wake cycles leading up to night shift (V1 to V2) was associated with significant changes in the placebo group in the concentration of serum cortisol (p = 0.01) ... In contrast, probiotic supplementation moderated changes in these serum markers from V1 to V2. No significant interaction effects (time by group) were observed for the serum markers prior to and after night shift work following probiotic supplementation due to the substantial changes in the serum markers that occurred during the normal sleep period from V1 to V2.