Changes in dietary intake, urinary nitrogen, and urinary volume across the menstrual cycle.

The effect of four menstrual cycle phases on changes in dietary intake, urinary nitrogen excretion, and urinary volume was examined in nine women confined to a metabolic unit, maintained at a constant activity level, and fed an ad libitum, rotating, staff-weighed diet. No significant changes in intakes of energy, protein, and fat occurred throughout the menstrual cycle although significant changes were found for intakes of ascorbic acid and water in food. A significant increase in consumption of carbonated, sugar-containing beverages was found in the luteal phase as was a significant increase in urine volume. Results suggest food choices and urine volume may be responsive to physiological regulators associated with hormonal changes in the menstrual cycle. Findings also suggest that energy intake is not altered across the menstrual cycle when physical activity is controlled and an accurate dietary assessment method is employed.