Fifty-three children with completed a six-week trial of kefir supplementation.
Kefir did not significantly reduce parent or teacher-rated ADHD symptom severity overall.
Children in the kefir group with higher baseline ADHD symptoms showed a trend towards lower scores by week six.
Kefir supplementation was associated with fewer minutes awake during the down period compared to the placebo group.
Post-intervention, the kefir group self-reported more sleep problems than the placebo group.
Kefir did not significantly affect diversity, but increased the abundance of certain beneficial bacteria.
Simplified
BACKGROUND: Evidence indicates the gut microbiome may be altered in , suggesting that targeting gut bacteria could alleviate symptoms. This study examined the effects of kefir supplementation on ADHD symptoms, sleep, attention, and gut microbiome composition in children diagnosed with ADHD.
METHODS: A six-week, randomised, double-blind, placebo-controlled trial was conducted in UK children aged 8-13 years with ADHD. Participants were assigned either to a daily kefir or placebo drink group. The primary outcome was ADHD symptom severity measured by the Strengths and Weaknesses of ADHD Symptoms and Normal Behaviour (SWAN) scale. Secondary outcomes included composition (analysed using shotgun metagenomic sequencing), gastrointestinal symptoms, sleep (actigraphy, parent/self-report), attention and impulsivity.
RESULTS: Fifty-three participants (mean age = 10.2 years, SD = 1.7) completed the study. Kefir had no significant overall effect on parent or teacher-rated ADHD symptom severity. A non-significant interaction was observed between baseline symptom severity and group for teacher-rated SWAN scores, with children in the kefir group who had the highest baseline ADHD symptoms showing lower scores at week six (M = 2.03, SE = 0.33 vs. 2.86, SE = 0.34), p = 0.088. Actigraphy revealed the kefir group spent fewer minutes awake during the down period at week six (M = 70.10, SE = 0.09) than the placebo group (M = 89.72, SE = 0.07), p = 0.04. However, the kefir group self-reported more sleep problems post-intervention (M = 39.81, SE = 0.75 vs. 37.40, SE = 0.65), p = 0.02. For Go/NoGo RT variance, a non-significant interaction (p = 0.052) between baseline and post intervention scores was found. No other significant group differences were observed. Kefir supplementation did not significantly affect gut microbiota alpha or beta diversity. However, relative abundance of several species including bifidobacterium adolescentis, B. infantis, and B. longum and Alistipes sp021204515 and A. timonensi increased significantly in the kefir group.
CONCLUSIONS: Kefir supplementation may support modest improvements in sleep quality, in children with ADHD. These findings contribute to our understanding of the potential role of nutrition in ADHD management and may inform clinical guidance for practitioners working with neurodivergent individuals.
ETHICS: Ethical approval for the study was granted by St Mary's University Ethics Committee.
TRIAL REGISTRATION: The trial protocol has been prospectively registered with ClinicalTrials.gov: NCT05155696. Registered on 13 December 2021.
Key numbers
70.10
Decrease in minutes awake
Kefir group's minutes awake during down period at week six
39.81
Self-reported sleep problems increase
Kefir group's total sleep problems score post-intervention
2.03
Non-significant trend in symptoms
Kefir group's SWAN score at week six for high baseline symptoms
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Declarations. Ethics approval and consent to participate: Ethical approval for the study was granted by St Mary’s University Ethics Committee (SMU_ETHICS_2020-21_240). The study adheres to the guidance listed in the latest version of the Declaration of Helsinki. All parents and children were provided with full written information about the study before written consent and assent were obtained. Consent for publication: Not applicable. Competing interests: Nourish Kefir supplied organic cow’s milk kefir for the study at a reduced cost. They exert no control over the publication of results. AG is an advisor for a project initially sponsored by Johnson’s Baby. She is a consultant for Perrigo (2021+). She receives royalties for two books Nodding Off (Bloomsbury Sigma, 2018) and The Sleepy Pebble (Flying Eye, 2019) and a sleep give product (The Gift of Sleep, Lawrence King Publishers, 2023). She was previously a CEO of Sleep Universal LTD (2022). She is a regular contributor to BBC Focus Magazine and has contributed to other outlets (such as The Conversation, The GuardianBalance Magazine, Psyche Aeon). She occasionally receives sample products related to sleep (e.g. blue light blocking glasses) and has given a paid talk to a business (Investec). She has contributed a paid article to Neurodiem. She occasionally receives speaking honoraria or expenses. KL previously held a paid role as Research Editor for Foodsmatter. She is an Editorial Board Member for the British Association of Nutritional and Lifestyle Medicine, Nutritional Evidence Database (NED) and a Scientific Advisory Board Member for Chuckling Goat, both in an unpaid capacity. She occasionally receives consultancy fees, speaking honoraria, hospitality, or sample products related to health and nutrition. PC is a co-founder and is the CTO of SeqBiome Ltd. He has also been occasionally paid, or received hospitality, to deliver talks on his research. The funders had no role in the design of the study; the writing of the manuscript, or in the decision to publish.
