Human Milk Oligosaccharides in Sports Nutrition: Biological Rationale and Current Evidence

Established sports-nutrition strategies support fueling, hydration, and muscle protein turnover, but strenuous exercise also challenges gastrointestinal, microbial, immune, metabolic, and musculoskeletal homeostasis. Human milk oligosaccharides (HMOs) are structurally diverse bioactive glycans that can selectively influence gut microbial composition, microbial metabolism, intestinal barrier integrity, and immune function. These properties provide a biological rationale for investigating HMOs in exercise and sports nutrition. This review critically evaluates direct and supportive evidence linking the biological functions of HMOs to exercise physiology. Human evidence is limited to two small trials. One examined supplementation alongside dietary restriction and increased physical activity, limiting conclusions about exercise adaptation; the other found no additional gains in muscle mass, strength, or anaerobic performance during resistance training. Alongside the emerging exercise-related findings, the established effects of HMOs on the gut microbiota and intestinal barrier also suggest a potential role in reducing exercise-associated gastrointestinal disturbances. However, benefits for these disturbances or post-exercise recovery have not been established. HMOs remain candidates for complementing established sports-nutrition strategies, but current evidence is insufficient to recommend supplementation for athletes. Future studies should determine how HMO structure, dose, formulation, and host characteristics influence gastrointestinal resilience, musculoskeletal adaptation, and functional outcomes in physically active populations. Establishing these relationships will be essential for translating HMOs into evidence-based sports-nutrition applications.