nesium pool available for milk production, or whether renal conservation is sufficient to meet the increased need, is unknown. Urinary magnesium concentrations in the lactating women were similar to those of nonlactating postpartum women; however, the 24-hour urinary magnesium losses in these lactating women were similar to urinary losses in women determined to be magnesium depleted based on the results of magnesium loading tests (Caddell et al., 1975). Although this study found lower urinary magnesium excretion in lactating women consuming an estimated daily average magnesium intake of 217 mg (9 mmol), another study found no difference in urinary magnesium concentrations between lactating and never-pregnant women who consumed higher average daily intakes of magnesium, around 270 mg (11.3 mmol) (Klein et al., 1995).

Currently, no consistent evidence exists to support an increased requirement for dietary magnesium during lactation. It appears that decreased urinary excretion of magnesium and increased bone resorption during lactation may provide the necessary magnesium for milk production. Therefore, the EAR and RDA are estimated to be the same as that obtained for nonlactating women of similar age and body weight.

Based on the 1994 CSFII intake data and adjusted for day-to-day variation (Nusser et al., 1996), the median intake of magnesium in 16 lactating women is 316 mg (13.2 mmol)/day; the fifth percentile of intake for the 16 women (of unspecified age) was 267 mg (11.1 mmol)/day (see Appendix D), which is slightly above the magnesium EAR for lactating women 19 through 30 years and close to the magnesium EAR of 265 mg (11.3 mmol)/day for lactating women ages 31 through 50 years. The twenty-