MAGNESIUM HOMEOSTASIS - CONSERVATION MECHANISM IN LACTATING WOMEN CONSUMING A CONTROLLED-MAGNESIUM DIET

This study was undertaken to determine whether lactating women consumi ng a low-magnesium diet compensate for magnesium secreted into breast milk by decreasing urinary magnesium losses. Six lactating (L) women, six nonlactating (NL) women (75 +/- 5 and 61 +/- 5 d postpartum, respe ctively), and seven never-pregnant (NP) women were studied while consu ming a constant magnesium intake of 8.97 +/- 0.01 mmol/d for 20 d. Aft er a 5-d stabilization period on the controlled diet, 24-h urine and f ecal samples were collected for the next 15 d. The L women excreted si gnificantly less (P < 0.01) urinary magnesium (2.10 +/- 0.35 mmol/d) t han the NP women (3.45 +/- 0.37 mmol/d). No significant differences we re detected in mean apparent magnesium absorption among the three grou ps of women, because of large individual variations of fecal magnesium and small sample size. L women apparently compensated for magnesium l osses in breast milk (1.04 +/- 0.06 mmol/d) by reducing urinary magnes ium losses (1.38 mmol/d) when consuming 8.97 mmol Mg/d.