Human gut health is closely related to sleep. We aimed to evaluate the efficacy of yeast mannan (YM) in improving bowel habits and sleep quality, along with metabolomics in fecal samples. A total of 40 healthy adults (age range, 22–64 years) with discomfort in defecation were enrolled and randomly allocated to receive either YM (n = 20; 1.1 g/day) or placebo (n = 20) for four weeks. Participants recorded their defecation habits throughout the test periods. Sleep electroencephalogram (EEG) recording using an EEG device and fecal sampling were performed pre- and post-treatment. The YM group significantly increased defecation frequency and stool volumes compared to the placebo group. After 4 weeks of treatment, the non-REM sleep stage 3 (N3) duration in the YM group was significantly higher than that in the placebo group. YM ingestion significantly lengthened total time in bed (TIB) and significantly shortened N3 latency compared to placebo intake during the trial. The metabolomics analysis found a total of 20 metabolite differences between the YM and placebo groups. As a result of stepwise linear regression, changes in fecal propionate and gamma-aminobutyric acid (GABA) levels were identified as the primary factors explaining changes in TIB and N3 latency, respectively. Our findings suggest that the prebiotic YM could be beneficial to gut health and sleep quality.

The purple-flesh potato (Solanum tuberosum L.) cultivar “Shadow Queen” (SQ) naturally contains anthocyanins. This randomized, double-blind, placebo-controlled study determines whether ingesting purple potatoes increases the number of mesenchymal stem cells (MSC) and improves stress response, a minor health complaint in healthy adults (registration number: UMIN000038876). A total of 15 healthy subjects (ages: 50–70 years) with minor health complaints were randomly assigned to one of two groups. For 8 weeks, the placebo group received placebo potatoes cv. “Haruka” and the test group received test potato cv. SQ containing 45 mg anthocyanin. The MSC count and several stress responses were analyzed at weeks 0 and 8 of the intake periods. The ingestion of a SQ potato did not affect the MSC count but markedly improved psychological stress response, irritability, and depression as minor health complaints compared with “Haruka”. No adverse effects were noted. Hence, an 8-week intake of SQ could improve stress responses.

Background: Evidence on food-based strategies to maintain muscle-related body composition in older adults under habitual lifestyle conditions is limited. Cacao flavanols may influence vascular and redox pathways, whereas milk protein provides amino acids relevant to muscle protein synthesis. We examined whether daily high-cacao chocolate, alone or with a protein-enriched milk beverage, affected body composition in community-dwelling older adults. Methods: This exploratory 16-week randomized, open-label, parallel-group trial included adults aged 60–79 years. Participants were allocated 1:1:1 to no intake (NI), high-cacao chocolate (HC; 15 g/day), or HC plus a protein-enriched milk beverage (HC+MILK; 200 mL/day). Body composition was assessed by multifrequency bioelectrical impedance analysis (BIA) at baseline, week 8, and week 16. Longitudinal models evaluated observed values and changes from baseline, and pairwise comparisons were adjusted using Tukey’s method. The per-protocol set was the primary efficacy population. Results: Of 240 randomized participants, 219 were included in the per-protocol set (NI, 76; HC, 72; HC+MILK, 71). At week 16, soft lean mass changed by − 0.24, + 0.21, and + 0.25 kg in NI, HC, and HC+MILK, respectively. Compared with NI, the change was + 0.45 kg with HC (95% CI 0.06 to 0.83; P = 0.015) and + 0.49 kg with HC+MILK (0.10 to 0.88; P = 0.005). Fat-free mass, skeletal muscle mass, and skeletal muscle index showed consistent significant differences versus NI, whereas HC+MILK did not differ from HC. No intervention-specific effect was observed for physical-function outcomes, and no product-related adverse events occurred. Conclusions: Over 16 weeks, HC and HC+MILK showed statistically significant favorable changes in BIA-derived muscle-related indices compared with NI, without a clear incremental benefit of adding MILK. These findings suggest a potential benefit for maintaining BIA-estimated muscle mass under habitual activity conditions, although the clinical relevance remains uncertain because no intervention-specific functional benefit was detected and changes in exercise type and intensity were not assessed comprehensively. Trial registration: UMIN000054576 (June 6, 2024).