Changes in Gut Flora Throughout Life and the Effectiveness of Age-Specific Probiotics

Abstract

Introduction: The human gut microbiota undergoes dynamic transformations throughout life, evolving from simple communities dominated by Bifidobacterium in infancy to diverse and stable adult ecosystems that later lose complexity with aging. This review synthesizes current scientific evidence on the evolution of gut microbiota across life stages and examines the effectiveness of specific probiotic strains according to age group. Development: During infancy, the microbiota shows low diversity and high instability, influenced by delivery mode, breastfeeding, and early antibiotic exposure. In childhood, diversity and functional maturity increase, with predominance of Firmicutes and Bacteroidetes. Adulthood represents the stage of greatest stability and diversity, characterized by an individualized “microbial fingerprint” shaped by diet, lifestyle, and geography. In old age, there is a marked reduction in Bifidobacterium and an increase in pro-inflammatory taxa associated with the inflammaging phenomenon, contributing to immunosenescence and reduced intestinal resilience. Probiotic effectiveness is both strain- and age-dependent: in infants and children, evidence is limited and heterogeneous; in adults, strains such as Lactobacillus plantarum P-8 and L. casei Zhang have demonstrated immunological and metabolic benefits; in the elderly, L. rhamnosus HN001 and L. acidophilus NCFM have been shown to enhance immune function and reduce Clostridium difficile. Conclusion: Probiotics represent a promising strategy to modulate the gut microbiota throughout the lifespan; however, significant gaps persist in clinical evidence. Future studies should aim to standardize doses, strains, and clinical endpoints, advancing toward personalized probiotic strategies guided by individual microbiome profiles to support healthy aging and disease prevention.