Molecular pathways and clinical applications of probiotics as effective supporters of intestinal, neurologic, and cardiovascular health: A narrative review.

This narrative review aims to synthesize current knowledge on the molecular mechanisms and clinical applications of probiotics across three major health domains: intestinal, neurologic, and cardiovascular. Intestinal health: Probiotics such as Lactobacillus rhamnosus GG and Bifidobacterium lactis BB-12 reinforce epithelial integrity via upregulation of tight-junction proteins (occludin, claudin-1), attenuate inflammation through cytokine modulation (↑IL-10, ↓TNF-α, IL-6), and restore eubiosis in conditions including IBS, constipation, and antibiotic-associated diarrhea. Neurologic health: "Psychobiotic" strains (e.g., L. rhamnosus JB-1, B. longum 1714, L. helveticus R0052 + B. longum R0175) modulate neurotransmitter synthesis (GABA, serotonin), dampen HPA-axis hyperactivity, and reduce neuroinflammation, yielding improvements in anxiety, stress resilience, cognitive function, and slowing brain-atrophy progression in MCI and Alzheimer's disease. Cardiovascular health: Meta-analyses of 30+ RCTs demonstrate that probiotic supplementation (notably L. acidophilus, L. plantarum, B. longum) lowers total and LDL cholesterol (-7 to -10 mg/dL) via bile-salt hydrolase activity, SCFA-mediated GPR signaling, direct cholesterol assimilation, and modestly reduces systolic (-2 to -4 mmHg) and diastolic blood pressure through anti-inflammatory pathways and improved endothelial function. Safety: While generally safe in healthy populations, rare adverse events (bacteremia, D-lactic acidosis, horizontal gene transfer) have been reported in immunocompromised or critically ill individuals, underscoring the need for individualized risk-benefit assessments and rigorous adverse-event surveillance. Probiotics exert strain-specific, multimechanistic benefits on gut barrier integrity, neuroendocrine signaling, and cardiometabolic regulation. To fully realize their therapeutic promise, future research must pursue large-scale, head-to-head clinical trials, integrate multiomics and precision-design approaches, and establish standardized frameworks for safety monitoring and personalized formulation.