Document is current

Article History

Received: 29 July 2025

Accepted: 27 October 2025

First Online: 24 November 2025

Declarations

:

: 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.

: Not applicable.

: 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.