Dry skin is one of the indicators of a compromised skin barrier. An intact skin barrier is not only important to reserve the hydration within the epidermal tissue but also to protect our skin from environmental stressors and inhibit pathogen invasion; damage to the skin barrier may lead to inflammatory skin diseases. Some microbial metabolites such as short chain fatty acids may inhibit or destroy harmful bacteria and regulate the host immune system. The impact of the skin microbiome and short chain fatty acids on skin barrier function was studied in two groups of 75 participants each. The cohort was equally divided in dry and moist skin types, based on stratum corneum (SC) functionality index (SCFI), reflecting the ratio of transepidermal water loss (TEWL). A dry group represents a low SCFI and a moist group a high SCFI. Compared with the dry skin group, propionate and Cutibacterium levels (previously known as Propionibacterium acnes) were significantly higher (p < 0.001) in the moist group. Levels of Cutibacterium were negatively correlated with those of Staphylococcus (p < 0.0001) in both dry and moist groups. The moist group also had a significantly higher propionate concentration (p < 0.001). This study showed that the microbial community and short chain fatty acid concentration may be considered as significant determinants of the SCFI of the skin.

Background/Objectives: Probiotic interventions are widely used to improve intestinal health; however, comparative evidence on multi-strain formulations with different po-tencies, particularly when combined with plant-based complexes, remains limited. eval-uated the effects of two probiotic blends containing phytonutrients (PBP1 and PBP2) on bowel function, microbial metabolites, and gut barrier-related markers. Methods: In this randomized, double-blind, placebo-controlled trial, participants received PBP1, PBP2, or placebo for 8 weeks. Stool patterns (7-day Bristol Stool Form Scale (BSFS) diary), fecal short-chain fatty acids (SCFAs), tryptophan metabolites, zonulin, and gut microbiota were assessed at baseline and Week 8. Efficacy was evaluated by comparing each inter-vention group with the placebo group. Results: Both PBP1 and PBP2 significantly in-creased the proportion of normal stool types (BSFS types 3–5) compared with placebo (p < 0.05). Fecal SCFA levels, including acetate, propionate, and butyrate, were significantly increased in both intervention groups. Notably, butyrate levels were significantly ele-vated compared with placebo. Fecal tryptophan levels decreased, while indole metabo-lites showed increasing trends, with an inverse correlation observed between tryptophan and indole, particularly in the PBP2 group. Fecal zonulin showed a decreasing trend, with significant reductions in participants with 25.0≤BMI<30.0 kg/m². Microbiome analysis revealed preserved alpha diversity with selective compositional shifts, including en-richment of Lactobacillus-related taxa. Conclusions: Supplementation with PBP1 and PBP2 improved bowel function and was associated with changes in microbiome-derived metabolites, including SCFAs and tryptophan–indole metabolism, with BMI-dependent changes in barrier markers. These findings suggest a potential role of microbi-ome-mediated metabolic modulation in intestinal health.

Phytonutrient-enriched prebiotic mixtures (PEPs), composed of phytonutrients and prebiotics that serve as substrates for beneficial gut microbes, are widely recognized for their potential to promote gut health. However, despite this established role, direct evidence demonstrating their synergistic effects when co-administered with probiotics remains limited. To address this gap, we employed a three-phase design integrating ex vivo evaluation and clinical validation to assess how individual components influence microbial responses, how PEP interacts with probiotics, and whether these effects translate to humans. In ex vivo analyses, PEP components were associated with increased levels of acetate, butyrate, total short-chain fatty acids (SCFAs), and lactate, with fiber-rich components showing the strongest effects. Co-treatment with probiotics further enhanced these metabolite levels compared to single treatments, particularly for butyrate and total SCFAs, along with elevated lactate levels. Notably, these effects became more pronounced with higher doses of co-administered probiotics, suggesting a dose-dependent enhancement of microbial metabolic activity and cross-feeding–mediated metabolic flux. In a randomized clinical study including PEP-only, probiotic-only, and combined PEP plus probiotic groups, all groups showed increases in fecal metabolites. However, the combined PEP and probiotic group exhibited the greatest increases in butyrate (~6 µmol/g) and total SCFAs (22.9 µmol/g). Across all groups, participants with constipation-type stool patterns shifted toward normal stool types, as assessed by the Bristol stool scale. These findings demonstrate that PEP modulates microbiome-derived metabolic activity, and that its combination with probiotics further enhances the production of butyrate and total SCFAs. Overall, this study provides both mechanistic and clinical evidence supporting synbiotic strategies and demonstrates the potential of PEP as an effective approach to improve gut microbial metabolism.

Phytonutrient-enriched prebiotic mixtures (PEPs), composed of phytonutrients and prebiotics serving as substrates for gut microbes, are recognized for their potential to modulate gut microbial metabolic activity. However, direct evidence of enhanced effects following co-administration with probiotics remains limited. Using a three-phase design integrating ex vivo evaluation and clinical validation, we assessed how PEP components influence microbial responses and whether co-administration with probiotics enhances these effects. PEP components increased acetate, butyrate, total short-chain fatty acids (SCFAs), and lactate, with fiber-rich components showing the strongest effects (all q < 0.0001 relative to negative control). Co-treatment with probiotics further enhanced butyrate and total SCFAs in a dose-dependent manner. In a randomized clinical study, all groups showed increases in fecal metabolites, with the combined group exhibiting the greatest increases in butyrate (+6.0 µmol/g, ~1.5-fold, p < 0.05) and total SCFAs (+22.9 µmol/g, ~1.3-fold, p < 0.05). Participants with constipation-type stool patterns shifted toward normal stool types across all groups. These findings support the utility of combined PEP and probiotic interventions for enhancing microbiome-derived metabolic activity.

Background/Objectives: Probiotic interventions are widely used to improve intestinal health; however, comparative evidence on multi-strain formulations with different potencies, particularly when combined with plant-based complexes, remains limited. This study evaluated the effects of two probiotic blends containing phytonutrients: PBP1, comprising Lacticaseibacillus strains, and PBP2, comprising Lacticaseibacillus, Lactobacillus, and Bifidobacterium strains. The effects on bowel function, microbial metabolites, and gut barrier-related markers were investigated. Methods: In this randomized, double-blind, placebo-controlled trial, participants received PBP1, PBP2, or placebo for 8 weeks. Stool patterns (7-day Bristol Stool Form Scale (BSFS) diary), fecal short-chain fatty acids (SCFAs), tryptophan metabolites, zonulin, and gut microbiota were assessed at baseline and Week 8. Efficacy was evaluated by comparing each intervention group with the placebo group. Results: Both PBP1 and PBP2 significantly increased the proportion of normal stool types (BSFS types 3–5) compared with placebo (p < 0.05). Fecal SCFA levels, including acetate, propionate, and butyrate, were significantly increased in both intervention groups. Notably, butyrate levels were significantly elevated compared with placebo. Fecal tryptophan levels decreased, while indole metabolites showed increasing trends, with an inverse correlation observed between tryptophan and indole, particularly in the PBP2 group. Fecal zonulin showed a decreasing trend, with significant reductions in participants with 25.0 ≤ BMI < 30.0 kg/m². Microbiome analysis revealed preserved alpha diversity with selective compositional shifts, including enrichment of Lactobacillus-related taxa. Conclusions: Supplementation with PBP1 and PBP2 improved bowel function and was associated with changes in microbiome-derived metabolites, including SCFAs and tryptophan–indole metabolism, with BMI-dependent changes in barrier markers. These findings suggest a potential role of microbiome-mediated metabolic modulation in intestinal health.