fifth percentile intake is 296 mg (12.3 mmol)/day, which is slightly below the EAR of 300 mg (13.8 mmol)/day for lactating women ages 14 through 18 years.

Special Considerations

Mothers Nursing Multiple Infants. Increased intakes of magnesium during lactation, as with calcium, should be considered in mothers nursing multiple infants concurrently. Magnesium requirements may be higher due to the increased milk production of a mother while nursing multiple infants. It is not known whether decreased urinary magnesium and increased maternal bone resorption provide sufficient amounts of magnesium to meet these increased needs.

TOLERABLE UPPER INTAKE LEVELS

Hazard Identification

Magnesium, when ingested as a naturally occurring substance in foods, has not been demonstrated to exert any adverse effects. However, adverse effects of excess magnesium intake have been observed with intakes from nonfood sources such as various magnesium salts used for pharmacologic purposes. Thus, a Tolerable Upper Intake Level (UL) cannot be based on magnesium obtained from foods. All reports of adverse effects of excess magnesium intake concern magnesium taken in addition to that consumed from food sources. Therefore, for the purposes of this review, magnesium intake that could result in adverse effects was from that obtained from its pharmacological use.

The primary initial manifestation of excessive magnesium intake from nonfood sources is diarrhea (Mordes and Wacker, 1978; Rude and Singer, 1980). Magnesium has a well-known cathartic effect and is used pharmacologically for that purpose (Fine et al., 1991b). The diarrheal effect produced by pharmacological use of various magnesium salts is an osmotic effect (Fine et al., 1991b) and may be accompanied by other mild gastrointestinal effects such as nausea and abdominal cramping (Bashir et al., 1993; Marken et al., 1989; Ricci et al., 1991). Osmotic diarrhea has not been reported with normal dietary intakes of magnesium. Magnesium ingested as a component of food or food fortificants has not been reported to cause this mild, osmotic diarrhea even when large amounts are ingested.

Magnesium is absorbed much more efficiently from the normal concentrations found in the diet than it is from the higher doses



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