RELATION BETWEEN SODIUM-BALANCE AND MENSTRUAL-CYCLE SYMPTOMS IN NORMAL WOMEN

Objective: To determine whether sodium balance affects expression of m enstrual symptoms. Design: Prospective study of menstrual symptoms dur ing three cycles: a baseline month (usual intake of sodium, 115 mmol/d ) followed by 2 months of sodium restriction (intake of sodium, 73.0 m mol/d). Added salt was allowed during the last month, Investigators we re aware of the diet sequence. Setting: Outpatient. Meals were prepare d by a metabolic kitchen during the 2 months that the participants rec eived salt-restricted diets. Participants: 13 healthy menstruant women . Measurements: Plasma sodium levels, urinary sodium excretion, and pl asma renin activity were measured for five time periods during the bas eline cycle and the two cycles of salt-restricted diet. Eleven women c ompleted a questionnaire assessing somatic symptoms and sensory cravin gs at the same time every day during the 3-month study period. Results : Sodium restriction was associated with a mean decrease (+/- one half of the 95% CI) in plasma sodium levels of 0.9 +/- 0.9 mmol/L from a m ean of 139.3 mmol/L during the baseline cycle (P = 0.018), a decrease in urinary sodium excretion of 40.3 +/- 18 mmol/d from a mean of 117 m mol/d during the baseline cycle (P = 0.001), and an increase in plasma renin activity of 0.14 +/- 0.08 ng/(L - s) from a mean of 0.28 ng/(L s) during the baseline cycle (P = 0.008). During the luteal phase of t he sodium restriction cycle, significant decreases in plasma sodium le vels of 1.23 +/- 0.5 mmol/L (from values of 138.8 mmol/L during the fo llicular phase) and increases in urinary sodium excretion of 27.2 +/- 10 mmol/d (from values of 65.5 mmol/d during the follicular phase) pre ceded periods when menstrual symptoms were most severe. Ratings of bre ast tenderness increased sixfold to eightfold in the late luteal phase (P < 0.001) and those of swelling or bloating increased twofold to th reefold during early menses (P < 0.001) compared with nadir symptom ra tings during each cycle. Sodium cravings increased in the luteal phase of all cycles but were not accompanied by increased sodium intake whe n access to added salt was allowed. Conclusions: Breast tenderness and bloating did not result from sodium retention in the luteal phase of the menstrual cycle. During normal and sodium-restricted diet cycles, women actually had urinary sodium loss, not retention, during the lute al phase; severity of menstrual symptoms was unchanged.