ZINC NEEDS AND HOMEOSTASIS DURING LACTATION

During lactation there is an increased maternal loss of the essential trace element zinc that is secreted into milk, During the first six mo nths of lactation a mean of approximately 1.1 mg d(-1) of zinc is secr eted into human milk, which decreases to 0.6 mg d(-1) during the next six months of lactation. The increased maternal need for zinc must be met through an increased dietary intake or homeostatic mechanisms whic h could compensate for the secretion of zinc into milk. These homeosta tic mechanisms may include an increase in absorption, reduced excretio n (urine and faecal endogenous Losses) and the use of maternal pools o f zinc, such as bone. Enhanced zinc absorption during lactation has be en reported for lactating women whose intake of zinc is less than half of the current recommendation. Urinary zinc excretion by lactating wo men has also been observed to be significantly decreased up to 6 month s pospartum compared to women who have never been pregnant. Approximat ely 30% of total body zinc is associated with bone. During lactation m aternal bone resorption and reduction in bone mineral content has been observed, Since urinary zinc excretion is reduced during lactation, t his bone resorption could supply a portion of the zinc that is incorpo rated into milk. Thus, during lactation, homeostatic mechanisms which include an enhanced zinc absorption, reduced urinary zinc excretion an d zinc from bone resorption could partially compensate for the secreti on of zinc into human milk. These homeostatic mechanisms need to be co nsidered when dietary recommendations for zinc intake are made for lac tating women.