Effects of Consumption of Black Soybean Seed Coat Extract on Sleep Quality in Healthy Japanese: A Randomized, Placebo-Controlled, Double-Blind, Parallel-Group Comparison Study

Abstract

This study examined the effect of the intake of a test food containing black soybean seed coat extract (BE) on the sleep quality of healthy Japanese adults with poor sleep quality. This double-blind, placebo-controlled, randomized, parallel-group trial included 94 participants. We randomly assigned 64 eligible participants to either (n = 32 per group) (i) the BE group receiving a BE-containing capsule daily or (ii) the Placebo group receiving a placebo capsule daily. The primary outcome was sleepiness on rising score in the Oguri-Shirakawa-Azumi sleep inventory MA (OSA-MA) at 12 weeks after intake, and the secondary outcomes were OSA-MA, PSQI-J, original questionnaire (visual analog scale), POMS2 scores, sleep test, blood flow, palmar surface temperature, and blood test data. The final analysis included data from 64 participants. The sleepiness on rising score was significantly higher in the BE group than in the placebo group. In the BE group, sleep-onset latency and subjective dry mouth significantly decreased, and palmar surface temperature significantly increased. Furthermore, BE effectively reduced sleepiness on rising in men and increased the total sleep duration in women. For participants aged ≥ 40 years, BE improved age-related decline in sleep quality and dry mouth. Increased deep sleep and reduced sleepiness on rising were observed in those with poor sleep quality. No adverse events were reported. BE intake promoted vasodilation and increased skin temperature, decreasing the sleep-onset latency and significantly improving rising sleepiness. The mechanism is attributed to BE's antioxidant and autonomic neuromodulatory effects. Trial Registration: UMIN-CTR: UMIN000051261.

Keywords: antioxidant activity; black soybean; blood flow improvement; polyphenols; sleep.

FIGURE 1

Participant flowchart.

FIGURE 2

Changes in each factor in the OSA‐MA. Changes in each factor (a, sleepiness on rising; b, initiation and maintenance of sleep; c, frequent dreaming; d, refreshing; e, sleep length) in the OSA‐MA among the full analysis set 1 are shown as means and standard error (SE) at Scr and as estimated marginal mean and SE at 4w and after. BE group (Scr and 4w: n = 32, 8w: n = 31, 12w: n = 30) and placebo group (Scr, 4w, and 8w: n = 32, 12w: n = 31). OSA‐MA, OSA sleep inventory MA version; Scr, screening (baseline); 4w, 4 weeks after consumption; 8w, 8 weeks after consumption; 12w, 12 weeks after consumption. *p < 0.05.

FIGURE 3

Changes in sleepiness on rising in the OSA‐MA in each subgroup. Changes in sleepiness on rising in the OSA‐MA in each subgroup (a, males of FAS1; b, females of FAS1; c, participants aged ≥ 40 years in FAS1; d, participants aged < 40 years in FAS1; e, participants whose score in sleepiness on rising in OSA‐MA was above or equal to the median (14.15 point) at Scr in FAS4; f, participants whose score on sleepiness on rising in OSA‐MA was below the median (14.15 point) at Scr in FAS4) are shown as mean and standard error (SE) at Scr and as estimated marginal mean and SE at 4w and after. (a) BE group (Scr and 4w: n = 16, 8w: n = 15, 12w: n = 14) and placebo group (Scr, 4w, 8w, and 12w: n = 16), (b) BE group (Scr, 4w, 8w, and 12w: n = 16) and placebo group (Scr, 4w, and 8w: n = 16, 12w: n = 15), (c) BE group (Scr and 4w: n = 20, 8w: n = 19, and 12w: n = 18) and placebo group (Scr, 4w, 8w, and 12w: n = 20), (d) BE group (Scr, 4w, 8w, and 12w: n = 12) and placebo group (Scr, 4w, and 8w: n = 12, 12w: n = 11), (e) BE group (Scr and 4w: n = 16, 8w and 12w: n = 15) and placebo group (Scr, 4w, 8w, and 12w: n = 16), (f) BE group (Scr, 4w, and 8w: n = 16, 12w: n = 15) and placebo group (Scr, 4w, and 8w: n = 16, 12w: n = 15). OSA‐MA, OSA sleep inventory MA version; FAS1, full analysis set1; FAS4, full analysis set4; Scr, screening (baseline); 4w, four weeks after consumption; 8w, eight weeks after consumption; 12w, 12 weeks after consumption. *p < 0.05.

FIGURE 4

Measured value of the palmar surface temperature and its AUC of in FAS3 and each subgroup. Data of the palmar surface temperature in FAS3 (a) and each subgroup (b, males of FAS3; c, participants aged ≥ 40 years in FAS3; d, participants whose score of sleepiness on rising in OSA‐MA was below the median (14.15 point) at Scr in FAS3 are shown as mean and standard error (SE) at Scr and as estimated marginal mean and SE at 12w. (a) BE group (Scr, 4w, 8w, and 12w: n = 29) and placebo group (Scr, 4w, 8w, and 12w: n = 31), (b) BE group (Scr, 4w, 8w and 12w: n = 13) and placebo group (Scr, 4w, 8w and 12w: n = 16), (c) BE group (Scr, 4w, 8w, and 12w: n = 17) and placebo group (Scr, 4w, 8w, and 12w: n = 20), (d) BE group and placebo group (Scr, 4w, 8w, and 12w: n = 15). Scr, screening (baseline); 12w, 12 weeks after consumption. *p < 0.05.