Abstract
BackgroundLactococcus lactis subsp. cremoris (YRC3780), which is isolated from kefir, has been associated with anti-allergic effects in humans. However, it remains unknown whether daily intake of YRC3780 attenuates the response to psychological stress in humans in parallel with changes to the gut microbiome. We examined the fundamental role of YRC3780 in the gut microbiome, stress response, sleep, and mental health in humans.MethodsEffects of daily intake of YRC3780 on the hypothalamic-pituitary-adrenal (HPA) axis response to acute psychological stress were investigated in a double-blind, placebo-controlled clinical trial involving 27 healthy young men (mean age and body mass index: 23.5 years and 21.5 kg/m2) who were randomly assigned to placebo (n = 13) or YRC3780 (n = 14) groups. The HPA axis response to acute psychological stress, the diurnal rhythm of HPA axis activity, and gut microbiome were assessed and compared between the two groups.ResultsThe results showed that daily intake of YRC3780 significantly lowered morning salivary cortisol levels compared with placebo. In addition, salivary cortisol levels following a social stress test significantly decreased +40 min after beginning the TSST in the YRC3780-treated group compared to placebo. There were no significant differences between the two groups in terms of actigraphy-based sleep quality, but the subjective sleep quality and mental health were significantly improved in the YRC3780-treated group compared to placebo.ConclusionsOur study suggests that daily intake of YRC3780 improves the HPA axis response to acute psychological stress, which might be associated with a decrease in morning cortisol levels.
Highlights
The hypothalamic-pituitary-adrenal (HPA) axis and sympathetic adrenomedullary (SAM) systems are major components of the stress response system [1]
An alternative mechanism involved in the alteration of the gut microbiota and/or the efficacy of probiotics on the stress response may be associated with the so-called gut-brain axis, a bidirectional interaction between the gut microbiome and the central nervous system [21]
We demonstrated that daily intake of YRC3780 decreased morning salivary cortisol levels 6 and 8 weeks after beginning daily ingestion (Fig. 2) and decreased the salivary cortisol response to acute psychological stress induced by the Trier Social Stress Test (TSST) (Fig. 3)
Summary
The hypothalamic-pituitary-adrenal (HPA) axis and sympathetic adrenomedullary (SAM) systems are major components of the stress response system [1]. Cremoris (YRC3780), which is isolated from kefir, has been associated with anti-allergic effects in humans It remains unknown whether daily intake of YRC3780 attenuates the response to psychological stress in humans in parallel with changes to the gut microbiome. METHODS: Effects of daily intake of YRC3780 on the hypothalamic-pituitary-adrenal (HPA) axis response to acute psychological stress were investigated in a double-blind, placebo-controlled clinical trial involving 27 healthy young men (mean age and body mass index: 23.5 years and 21.5 kg/m2) who were randomly assigned to placebo (n = 13) or YRC3780 (n = 14) groups. CONCLUSIONS: Our study suggests that daily intake of YRC3780 improves the HPA axis response to acute psychological stress, which might be associated with a decrease in morning cortisol levels.
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