In a groundbreaking clinical trial published in BMC Psychiatry, researchers explored the potential of kefir, a fermented dairy product known for its probiotic properties, in alleviating symptoms of Attention Deficit Hyperactivity Disorder (ADHD) in children. This six-week, meticulously designed randomised, double-blind, placebo-controlled study sheds new light on the intriguing link between gut microbiota modulation and neurodevelopmental conditions, potentially opening new avenues for nutritional interventions in ADHD management.
The investigation targeted children aged 8 to 13 in the United Kingdom diagnosed with ADHD, focusing primarily on how a daily dose of kefir influences symptom severity. The trial utilized the Strengths and Weaknesses of ADHD Symptoms and Normal Behaviour (SWAN) scale as a quantitative measure, ensuring that outcomes were grounded in rigorous clinical assessment standards. This methodical approach enabled the team to objectively capture complex behavioral changes linked to probiotic supplementation.
While overall ADHD symptom severity, as rated by parents and teachers, did not show a significant shift across the intervention period, nuanced observations emerged. Specifically, children with more severe baseline symptoms exhibited a trend toward improvement in teacher-rated SWAN scores after kefir administration, hinting at a possible subgroup-specific effect. Although the results did not reach conventional statistical significance (p=0.088), this trend offers a promising signal that warrants further investigation with larger sample sizes and longer follow-ups.
The study also employed sophisticated actigraphy to quantify sleep quality, providing an objective dimension to the behavioral analysis. Remarkably, participants in the kefir group demonstrated fewer minutes awake during designated “down periods,” suggesting improved sleep consolidation. This finding is significant given the pervasive sleep disturbances commonly reported in children with ADHD, linking probiotic intake with tangible enhancements in sleep physiology.
Conversely, paradoxical findings emerged from self-reported sleep evaluations, where children in the kefir group reported increased sleep difficulties post-intervention. This divergence between objective and subjective sleep metrics underscores the intricate interplay between neuropsychological states and perception, emphasizing the need for multi-modal assessment strategies in clinical research.
Beyond symptomatic and sleep metrics, the researchers harnessed shotgun metagenomic sequencing to profile gut microbiota with unprecedented resolution. Although global measures of microbial diversity, such as alpha and beta diversity indices, remained unchanged, kefir supplementation significantly enhanced the relative abundance of specific bacterial taxa. Notably, several species of the Bifidobacterium genus, including B. adolescentis, B. infantis, and B. longum, showed marked increases, as well as species within the Alistipes genus.
These microbiome shifts have profound implications, considering that bifidobacteria are often associated with anti-inflammatory and gut barrier-supportive roles. The modulation of these beneficial microbes may influence neuroimmune pathways and neurotransmitter synthesis, potentially underpinning the subtle behavioral and sleep improvements observed. The rise in Alistipes species, although less studied, suggests complex microbial ecosystem adjustments triggered by kefir’s unique microbial consortium.
Importantly, while improvements were modest and did not extend to all measured outcomes such as attention or impulsivity (evaluated through Go/NoGo task reaction time variance), the trial pioneers a novel nutritional approach targeting gut-brain axis dynamics in a pediatric neurodevelopmental disorder. These preliminary findings provide critical data to inform clinical guidance, particularly given the increasing interest in complementary and integrative therapies for ADHD beyond pharmacological interventions.
Ethical rigor was maintained throughout the trial, with approval granted by St Mary’s University Ethics Committee, ensuring compliance with standards for studies involving vulnerable populations such as children. The trial was registered prospectively at ClinicalTrials.gov (NCT05155696), reinforcing transparency and scientific integrity.
As the field of psychobiotics progresses, this study adds a valuable clinical dimension to an expanding base of preclinical and observational research suggesting gut microbiota modulation as a potential therapeutic lever. Future investigations are needed to elucidate underlying mechanisms, optimal dosages, and long-term effects, with the possibility that personalized nutrition could become an adjunctive strategy tailored to individual microbial and clinical profiles.
In summary, while kefir supplementation did not dramatically transform ADHD symptomatology, it demonstrated potential benefits on sleep architecture and gut microbial composition. This pioneering trial bridges nutrition science and neuropsychiatry, cultivating hope for non-pharmacological adjuncts that harness the microbiome in optimizing the wellbeing of neurodivergent children.
Subject of Research: Effects of kefir supplementation on ADHD symptoms, sleep quality, and gut microbiome composition in children diagnosed with ADHD.
Article Title: Effects of kefir on symptoms, sleep, and gut microbiota in children with ADHD: a randomised controlled trial.
Article References:
Lawrence, K., Fibert, P., Toribio-Mateas, M. et al. Effects of kefir on symptoms, sleep, and gut microbiota in children with ADHD: a randomised controlled trial. BMC Psychiatry 25, 1117 (2025). https://doi.org/10.1186/s12888-025-07568-8
Image Credits: AI Generated
DOI: 24 November 2025
