Probiotic Lactobacillus plantarum P8 alleviated stress and anxiety while enhancing memory and cognition in stressed adults: A randomised, double-blind, placebo-controlled study

Clin Nutr. 2019 Oct;38(5):2053-2064. doi: 10.1016/j.clnu.2018.09.010. Epub 2018 Sep 19.


Background & aims: To investigate the effects of probiotic in alleviation of stress in stressed adults, along our focus to identify and justify strain specificity on selected health benefits with a precisely targeted population.

Methods: This 12-weeks randomized, double-blind and placebo-controlled study investigated the effects of a probiotic (Lactobacillus plantarum P8; 10 log CFU daily) on psychological, memory and cognition parameters in one hundred and three (P8 n = 52, placebo n = 51) stressed adults with mean age of 31.7 ± 11.1 years old. All subjects fulfilled the criteria of moderate stress upon diagnosis using the PSS-10 questionnaire.

Results: At the end of study, subjects on P8 showed reduced scores of stress (mean difference 2.94; 95% CI 0.08 to 5.73; P = 0.048), anxiety (mean difference 2.82; 95% CI 0.35 to 5.30; P = 0.031) and total score (mean difference 8.04; 95% CI 0.73 to 15.30; P = 0.041) as compared to placebo after 4-weeks, as assessed by the DASS-42 questionnaire. Although plasma cortisol levels were only marginally different between placebo and P8 (mean difference 3.28 ug/dl; 95% CI -7.09 to 0.52; P = 0.090), pro-inflammatory cytokines such as IFN-γ (mean difference 8.07 pg/ml; 95% CI -11.2 to -4.93; P < 0.001) and TNF-α (mean difference 1.52 pg/ml; 95% CI -2.14 to -0.89; P < 0.001) showed higher reduction as compared to placebo over 12-weeks. These were accompanied by enhanced memory and cognitive traits such as social emotional cognition and verbal learning and memory upon administration of P8 as compared to the placebo, with different effects in women as compared to men.

Conclusions: The present data illustrated that L. plantarum P8 is a feasible and natural intervention for the alleviation of selected stress, anxiety, memory and cognitive symptoms in stressed adults.

Trial registration: Approved by the JEPeM-USM Review Panel on Clinical Studies (Approval number USM/JEPeM/16050195) and was registered at (identifier number NCT03268447).

Keywords: Anxiety; Cognition; Gut-brain-axis; Lactobacillus plantarum P8; Memory; Stress.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anxiety / drug therapy*
  • Cognition / drug effects*
  • Cytokines / blood
  • Double-Blind Method
  • Female
  • Gastrointestinal Microbiome
  • Humans
  • Hydrocortisone / blood
  • Lactobacillus plantarum*
  • Male
  • Memory / drug effects
  • Middle Aged
  • Probiotics* / administration & dosage
  • Probiotics* / pharmacology
  • Probiotics* / therapeutic use
  • Stress, Psychological / drug therapy*
  • Young Adult


  • Cytokines
  • Hydrocortisone

Associated data