Abstract

Malnutrition remains a major global health burden, disproportionately affecting children under five years of age in 
low- and middle-income countries. It is characterized by inadequate or excessive nutrient intake, leading to 
stunting, wasting, underweight, or obesity, with significant consequences for morbidity, mortality, and long-term 
development. Recent evidence highlights the role of the human gut microbiome as a central player in nutritional 
health, influencing nutrient absorption, immune responses, and metabolic pathways. Alterations in the 
composition and function of the microbiome, often referred to as dysbiosis are increasingly linked to 
undernutrition and overnutrition. Case studies in children and adults reveal that malnourished individuals harbor 
immature or disrupted microbiomes, with reduced microbial diversity, enrichment of pathogenic taxa, and 
impaired production of essential metabolites such as short-chain fatty acids and vitamins. These findings 
underscore a bidirectional relationship in which malnutrition shapes microbial ecology, while microbiome 
alterations exacerbate nutrient deficiencies and disease susceptibility. Interventions such as probiotics, prebiotics, 
dietary modifications, microbiota-directed complementary foods, and fecal microbiota transplantation represent 
promising approaches for restoring microbial balance and improving nutritional outcomes. However, challenges 
such as variability in research methods, ethical concerns, and limited evidence from large-scale trials hinder 
translation into policy and clinical practice. Advances in metagenomics, metabolomics, and culturomics provide 
new opportunities for understanding microbiome–nutrition interactions and developing targeted therapies. This 
review synthesizes current evidence linking the microbiome and malnutrition, discusses therapeutic opportunities, 
and emphasizes the need for integrated public health and policy strategies to reduce the global burden of 
malnutrition.