Emerging evidence suggests that microorganisms acting via the Brain-Gut axis may have potential benefits for the management of stress-related conditions. The majority of studies have focused on animal models. Preclinical studies have identified the Lactobacillus Rhamnosus JB-1 strain as a putative psychobiotic with an impact on stress-related behaviours, physiology and cognitive performance. Whether such preclinical effects could be translated to healthy human volunteers remains unknown.

30 healthy male volunteers will be recruited in a randomized single blind placebo controlled cross over trial. Study participation will involve a screening visit followed by a baseline cognitive test battery, EEG and stress visit (socially evaluated cold-pressor test). These measures will be repeated after 4 weeks of daily probiotic and placebo capsules.

Inclusion Criteria:

• able to give informed written consent
• able to speak English

Exclusion Criteria:

• having a significant acute or chronic illness
• following a diet or taking a medication that would interfere with study objectives
• pose a safety risk or confound the interpretation of the study results
• evidence of immunodeficiency, bleeding disorder or coagulopathy
• English not being participant's first language
• colour blindness
• dyslexia or dyscalculia
• taking any probiotic products or antibiotics in the last 4 weeks
• receiving any treatment involving experimental drugs