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The Keele Study

A double-blind, placebo-controlled, randomised pilot trial examining the effects of probiotic administration on mood and cognitive function


This randomised, double blind, placebo controlled study examined the effects of Lab4 probiotics on general feelings of anxiety, mood and cognitive function in healthy individuals.


  • The study took place at the School of Psychology at Keele University.
  • 50 healthy volunteers (19-38 years old, BMI<30) were divided into two groups.
  • One group was supplemented with 50 billion Lab4 probiotics every day for six weeks.
  • The second group took a placebo daily for 6 weeks
  • Volunteers completed mood and anxiety questionnaires (Bond Lader Mood Scales, Stait Trait Anxiety Inventory)
  • Participants also completed a comprehensive computerised cognitive battery of tests (COMPASS)

The results

‘Trait’ Anxiety
(individual’s tendency to experience anxiety in response to the anticipation of a future threat, how individuals felt over the previous 6 weeks)

  • Lab4 probiotics significantly decreased ‘trait’ anxiety levels compared to the placebo group, where the ‘trait’ anxiety levels increased over the course of the 6 weeks supplementation (P=0.042).

‘Continuity of attention’
(ability to focus and avoid distraction)

  • ‘Continuity of attention’ significantly increased in response to the Lab4 supplementation and decreased in the placebo group (P=0.035).
Trait Anxiety - The Keele Study
Trait Anxiety - The Keele Study


The study showed the benefit of Lab4 probiotics for cognitive function in healthy individuals.


Owen L, et al 2014.
A double blind, placebo controlled, randomised pilot trial examining the effects of probiotic administration on mood and cognitive function.
Proceedings of the Nutrition Society 2014, 73 (OCE1): E29

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