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Stewart, Laura K.

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Cannabidiol (CBD) has increased in popularity since the United States Farm Bill legalized hemp production in 2018 and is now projected to become a $24.4 billion dollar industry by 2025. Since its legalization, CBD is thought to be an antiepileptic, anxiolytic, and antipsychotic, as well as an agent to improve mental health, quality of life, aspects of sleep and immune function. However, many of these claims lack scientific evidence. The purpose of this randomized, double blind, placebo-controlled trial was to determine the effects of an 8-week CBD intervention on measures of mental health, sleep quantity, sleep quality, and natural killer cell (NKC) quantity and function. Researchers hypothesized that following an 8-week CBD intervention, participants consuming CBD will experience improvements in measures of mental health, increased sleep quantity and quality, and will have an increased percentage of NKC in peripheral blood, as well as decreases in NKC function determined by a measure of K562 cell viability. Physically active men and women (18-45y) were randomly assigned to placebo (CN, n=12) or CBD (CB, n=15) groups. Participants consumed a capsulized control; coconut derived medium chain triglycerides (MCT; 225mg/day) or CBD (50mg/day with 175mg of MCT) daily for 8 weeks. Before and after the intervention period, participants completed measures of mental health, sleep analysis (FITBIT), body size, body composition (BodPod), a peripheral blood draw, anaerobic fitness (Wingate), aerobic fitness (VO2max), 1 repetition strength testing (1RM). Peripheral blood mononuclear cells (PBMC) were extracted from peripheral blood to determine immune cell population percentages, and natural killer cell (NKC) cytotoxicity. Immune population percentage measures involved, staining the cells with anti-CD3 and anti-CD56 for the determination of NKC (CD3-/CD56+), T cells (CD3+/CD56-) and natural killer T cells (NKT; CD3+/CD56+). NKC cytotoxicity analysis involved co-incubated of PBMC with K562 leukemia cells for 4 hours at ratios of 1:1, 5:1, 10:1, and 20:1 effector: target cell (E:T). K562 cell viability was determined using median fluorescence intensity using a flow cytometer. Data are presented as mean ± standard deviation with significance set at α=0.05. An independent-samples T-test was ran on all outcome measures at the pre intervention time point to ensure homogeneity between groups, and a 2 (group) x 2 (time) analysis of variance (ANOVA) was used to identify any interactions or main effects that occurred throughout the intervention. At the pre intervention time points, there were no significant differences between groups with respect to participant anthropometrics or exercise performance measures (age: 26.1 ± 6.2y; height: 169 ± 8.8cm; weight: 71.6 ± 12.8kg; lean body mass: 55.8 ± 11.3kg; body fat: 21.8 ± 8.3%; Peak Power: 647.8 ± 169.9W; Mean Power: 459.1 ± 121.1W; Anaerobic Fatigue: 56.9 ±7.2%; VO2Peak: 45.0 ± 7.6ml/kg/min; 1RM Squat: 88.2  31.4kg; 1RM Bench:61.43  28.44kg); however, VO2Peak significantly decreased after 8-weeks regardless of intervention group (p=0.038; Pre: 45.05 ± 7.61 Post: 43.75 ± 7.34ml/kg/min). There were no significant differences pre to post intervention between groups in measures of mental health (QOL; Pre: 9.49 ± 1.82 Post:19.81 ± 1.42; PFS; Pre: 3.22 ± 1.58 Post:2.74 ± 1.58; BDI; Pre: 4.56 ± 3.83 Post: 4.44 ± 3.72; GAD-7; Pre: 6.3 ± 6.0 Post: 4.9 ± 4.3), sleep quantity (TST; Pre: 386.75 ± 67.69 Post: 388.92 ± 57.89min) or sleep quality (WE; Pre: 26.44 ± 7.53 Post: 26.16 ± 7.70; SE; Pre: 88.41 ± 1.46 Post: 88.02 ± 1.93%). Furthermore, the fraction of NKC within 1x106 peripheral blood mononuclear cells remained unchanged (Pre: 8.44 ± 5.34% Post: 8.79 ± 4.12%), following the intervention period. Finally, there were no differences in K562 cell viability assessed through mean and median fluorescence intensity of Calcein-AM, following an 8-week CBD intervention. Eight weeks of CBD (50mg/day) did not alter measures of mental health, sleep quantity or quality, NKC percentage in peripheral blood or NKC function. This suggests that CBD may not alter mental health, sleep quantity, sleep quality, NKC percentage in peripheral blood or NKC cytolytic function.


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