Efficacy of a fish hydrolysate supplement on sleep quality: A randomized, double-blind, placebo-controlled, crossover clinical trial

Background & aims: Sleep disturbances are widespread in modern societies and linked to a variety of diseases, creating an urgent need for the development of products that help combat sleep difficulties. One suitable nutritional supplement may be a fish hydrolysate composed of low molecular weight peptides. Methods: This two -arm, double-blind, randomized, placebo -controlled crossover study investigated the effect of a 4 -week fish hydrolysate intervention on sleep in a healthy German population reporting poor sleep quality, assessed with the Pittsburgh Sleep Quality Index (PSQI). Further sleep parameters were measured using an online diary and a wrist wearable device. Additionally, questionnaires related to stress, anxiety, depression, and well-being were evaluated and salivary cortisol and product satisfaction were assessed. Results: The 4 -week fish hydrolysate supplementation significantly improved subjective sleep quality measured with the PSQI-score (p = .002). Moreover, individuals reported improvements in sleep efficacy and a reduction in sleep disturbances and daytime sleepiness during fish hydrolysate intake (p = .013, p = .046, p = .004 respectively), but not during placebo phase (all p > .05). No significant intra-individual differences were found between fish hydrolysate and placebo supplementation (p > .05). Conclusions: Although no significant intra-individual differences were found between fish hydrolysate and placebo supplementation, the significant improvement in subjective sleep quality from baseline to treatment phase suggests that fish hydrolysate is a safe nutritional supplement to support individuals with self -reported sleep problems. Clinical trial registration: The study is registered at ClinicalTrials.gov with the Identifier NCT04 983355. (c) 2024 The Authors. Published by Elsevier Ltd on behalf of European Society for Clinical Nutrition and Metabolism. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).