The effects of waxy barley on defecation, sleep, mental health, and quality of life: A randomized double-blind parallel-group comparison study

Background Dietary fiber (DF) is beneficial for preventing constipation, and the metabolites produced by gut microbiota fermentation are suggested to positively influence on depression and sleep. Additionally, constipation has been reported to affect mental health and health-related quality of life (HRQoL). This study aimed to increase DF intake and examined its effects on daily DF and β-G consumption using two types of waxy barley (WB), rich in DF with varying β-glucan (β-G) content. Additionally, this study examined the effects of WB consumption on defecation, sleep, mental health, and HRQoL. Methods A randomized double-blind parallel-group comparison study was conducted on 68 young Japanese women, using Kirarimochi (Group K) as common WB cultivar and Fukumi Fiber (Group F) as high-β-G WB cultivar. Participants consumed WB rice for four weeks, targeting 3 g/day of β-G (48 g/day of WB). We estimated the intake of WB and DF including β-G from the daily records. Defecation was evaluated through daily records and Rome IV criteria-based surveys. Sleep, mental health, and HRQoL were evaluated using PSQI-J, J-PHQ-9, and SF-36, respectively. Results Both groups consumed about 40 g/day of WB. DF and β-G intakes from barley were 6.3 g/2.5 g in Group K and 10.7 g/4.3 g in Group F. Regarding defecation, both groups showed increases defecation days, defecation frequency and stool amount, with no differences between groups. Regarding sleep, Group F showed a decrease (improvement) in the PSQI global score, with improvements noted between groups. Regarding mental health, both groups showed decreases (improvements) in the PHQ-9 score, with Group F showing improvement between groups. Regarding HRQoL, summary scores showed improvements: physical health in Group K and mental health in Group F. Conclusion To increase β-G intake, high-β-G WB cultivars are effective; however, WB cultivars overall can potentially serve as excellent sources of DF. Effects on defecation may be expected not only from high-β-G WB but also from common WB with β-G intake below the target of 3 g/day. Although high β-G WB may have more beneficial for sleep and mental health, additional studies are required.