**2. Methodology**

A narrative review was conducted between March and November 2020. The narrative review was supported by a semi-systematic approach to article searching, and specific inclusion and exclusion criteria, so that articles reviewed were relevant to athletes and sporting environments. Initial studies of interest were located through a search of six databases (PubMed, Scopus, CINAHL, EMBASE, SPORTDiscus, and Google Scholar) from inception up to November 2020. The following search terms were used: nutrition OR nutritional intervention AND sleep AND athletes OR athlete OR team-sport OR sportsman OR sportswoman. Another search was conducted using the following search terms: nutrition OR nutritional intervention AND sleep, to find interventions based on other populations.

Studies were included in the review if they were experimental, including randomized controlled trials, observation studies, case studies, and case reports conducted in elite or semi-elite athlete cohorts. Given the paucity of sleep nutrition research in the athlete population, we expanded our inclusion criteria to include studies that reported the outcomes of nutritional interventions to improve sleep in otherwise healthy adults. Studies were excluded if they included participants with concussions, included participants with other disorders unrelated to sleep, participants in shift work, described longitudinal dietary adjustment (e.g., low carbohydrate dieting), or an animal study. Reference lists of selected articles were also inspected to ensure all relevant literature was captured for review. The

outcomes of nutritional intervention on sleep were detailed in four variables following existing recommendations [20]:


Given this study was a review, no ethics approval was required. Narrative synthesis was used to investigate and interpret both similarities and differences between studies identified with the two systematic searches, and other secondary sources deemed relevant by the research team.
