An Overview of the Impact of the Menstrual Cycle on Nutrient Metabolism: An Integrative Perspective.

The menstrual cycle represents a dynamic infradian rhythm characterized by coordinated fluctuations in ovarian steroids that extend beyond reproductive function and influence systemic metabolism. This narrative review synthesizes current evidence on how menstrual cycle phase modulates energy balance, macronutrient metabolism, micronutrient handling, and responses to dietary bioactive compounds. Across phases, small-to-moderate but consistent differences emerge in energy intake, resting energy expenditure, substrate utilization, and protein turnover, with a tendency toward increased energy intake and lipid oxidation during the mid-luteal phase compared with the early follicular and peri-ovulatory phases. Emerging metabolomics data further reveal coordinated cyclical variation in amino acids, B vitamins, and lipid species, suggesting temporally sensitive windows in which low energy availability or micronutrient insufficiency may more readily impair performance, recovery, or symptom burden. Importantly, menstrual cycle-related metabolic variability reflects not only estradiol and progesterone oscillations but also integrated adaptations across the hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune signaling, and gut microbiota. These interconnected systems contribute to inter- and intra-individual heterogeneity in metabolic phenotype. From a clinical and applied perspective, the evidence supports "cycle-aware" but non-dogmatic nutritional strategies, particularly in contexts of metabolic dysfunction, high training loads, or reproductive disorders. Future research should systematically verify cycle phase, incorporate multi-system biomarkers, and adopt sex-specific analytical frameworks to improve translational relevance. Recognizing the menstrual cycle as a biologically meaningful metabolic variable may enhance precision nutrition, exercise prescription, and metabolic risk assessment in women.