Phytonutrient-Enriched Prebiotic Mixture Primes the Gut Environment to Enhance Probiotic Efficacy: Ex Vivo Screening and a Human Clinical Trial

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.