Effect of the menstrual cycle on postprandial blood glucose levels across meals in young females

This study investigated the effect of the menstrual cycle phase on postprandial blood glucose across meals in young females. Additionally, associations between glucose responses and sex hormone concentrations at each time point were assessed. Fifteen healthy young females (aged 24.9 ± 0.8 years) participated in two trial phases: (1) the follicular phase (Days 9-11 of menstruation) and (2) the luteal phase (Days 21-23). On each trial day, participants consumed test meals of identical composition at breakfast, lunch, and dinner. Postprandial blood glucose levels were measured using a continuous glucose monitoring system. Salivary estradiol and progesterone concentrations as well as core body temperature were recorded to determine the menstrual phase and examine associations with glycaemic fluctuations. No significant differences were observed between phases in postprandial glucose concentrations after breakfast or lunch. However, glucose levels 30 min after dinner were significantly higher during the luteal phase than during the follicular phase (p = 0.043). Estradiol concentrations did not differ significantly between phases at any time point, whereas progesterone levels were significantly elevated during the luteal phase at all meal times (breakfast: p = 0.005; lunch: p = 0.001; dinner: p = 0.001). Core body temperature at waking, and mean, maximum, and minimum bedtime temperatures were significantly higher in the luteal phase (p = 0.004, 0.023, 0.050, and 0.020, respectively). These findings may inform menstrual phase-specific strategies for managing postprandial glycaemia.