title: Zinc absorption and kinetics during pregnancy and lactation in Brazilian women. Prenatal iron supplements impair zinc absorption in pregnant Peruvian women. A longitudinal study of urinary calcium, magnesium, and zinc excretion in lactating and nonlactating postpartum women. Maternal zinc supplementation does not affect size at birth or pregnancy duration in Peru. Adding zinc to prenatal iron and folate supplements improves maternal and neonatal zinc status in a Peruvian population. Maternal zinc supplementation and growth in Peruvian infants. Zinc homeostasis during lactation in a population with a low zinc intake. Zinc nutritional status during pregnancy: a longitudinal study. A longitudinal study of pyridoxine and zinc supplementation of lactating women. Low Zinc Intake During Exclusive Breast‐Feeding Does Not Impair Growth The effect of zinc supplementation on pregnancy outcome. A study of the effect of oral zinc supplementation during pregnancy on pregnancy outcome. Zinc, calcium, and magnesium concentrations in milk from American and Egyptian women throughout the first 6 months of lactation. Zinc supplementation during lactation: effects on maternal status and milk zinc concentrations.
abstract: BACKGROUND Adjustments in zinc absorption and endogenous excretion maintain zinc homeostasis in nonpregnant adults fed low-zinc diets . The effects on zinc homeostasis of a low zinc intake during pregnancy and lactation have not been described in a longitudinal study . OBJECTIVE We examined longitudinal changes in fractional zinc absorption ( FZA ) and zinc kinetics in 10 healthy Brazilian women who habitually consumed a marginal zinc diet ( approximately 9 mg Zn/d ) . DESIGN  Zinc status was measured at 10 - 12 ( early pregnancy ; EP ) and 34 - 36 ( late pregnancy ; LP ) wk of pregnancy and at 7 - 8 wk after delivery ( early lactation ; EL ) . Zinc kinetics and FZA were studied by using stable isotopic tracers . RESULTS Zinc intake averaged 9 + /- 3 mg/d throughout the study . FZA increased from 29 + /- 6 % at EP to 43 + /- 10 % at LP and to 39 + /- 13 % at EL ( P < 0.05 ) . FZA was inversely related to plasma zinc at EL ( r = -0.73 , P = 0.02 ) and LP ( r = -0.72 , P = 0.07 ) . Plasma zinc mass was 23 % greater at LP than at EP or EL ( P < 0.05 ) . The amount of zinc ( mg/d ) that fluxed between plasma and the most-rapidly-turning-over extravascular pool was 53 % greater at LP than at EP or EL ( P < 0.05 ) . The zinc flux between plasma and the less-rapidly-turning-over zinc pool at EL was 27 % greater than that at EP or LP , but this difference was not significant . CONCLUSIONS FZA increased significantly in women with marginal zinc intakes during pregnancy and lactation ; the increase was higher in women with low plasma zinc . Plasma zinc was distributed into a different exchangeable pool at LP than at EL Prenatal iron supplements may adversely influence zinc absorption during pregnancy . To examine the impact of prenatal iron supplements on supplemental zinc absorption , fractional zinc absorption was measured in 47 pregnant Peruvian women during the third trimester of pregnancy ( 33 + /- 1 wk gestation ) . Of these 47 women , 30 received daily prenatal supplements  from wk 10 - 24 of pregnancy until delivery . Supplements contained 60 mg of Fe and 250 microg of folate without [ iron group ( Fe ) , n = 16 ] or with [ iron and zinc supplemented group ( Fe + Zn ) , n = 14 ] 15 mg of Zn . The remaining 17 women [ unsupplemented control group ( C ) ] received no prenatal supplementation .  Zinc concentrations were measured in plasma , urine and cord blood and percentage zinc absorption was determined following dosing with oral ( (67)Zn ) and intravenous ( (70)Zn ) stable zinc isotopes . Percentage zinc absorption was significantly lower than controls in fasting women receiving iron- containing prenatal supplements ( 20.5 + /- 6.4 vs. 20.2 + /- 4.6 vs. 47.0 + /- 12.6 % , Fe , Fe + Zn and C groups , respectively , P : < 0.0001 , n = 40 ) . Plasma zinc concentrations were also significantly lower in the Fe group compared to the C group ( 8.2 + /- 2.2 vs. 9.2 + /- 2.2 vs. 10.9 + /- 1 . 8 micromol/L , Fe , Fe + Zn and C groups , respectively , P : = 0.002 ) , and cord zinc concentrations were significantly related to maternal plasma Zn levels ( y = 6.383 + 0.555x , r = 0.486 , P : = 0.002 ) . The inclusion of zinc in prenatal supplements may reduce the potential for iron supplements to adversely influence zinc status in population s at risk for deficiency of both these nutrients Postpartum lactating ( n = 12 ) and nonlactating ( n = 11 ) women and never pregnant women ( n = 14 ) collected urine sample s and diet records 2 d each month for 6 mo to determine whether postpartum women conserved urinary calcium , magnesium , or zinc . Mean daily excretions were analyzed by repeated- measures analysis of variance and covariance to assess group and time effects . Lactating women excreted less urinary calcium ( 1 - 6 mo ) than never pregnant ( n = 8) and nonlactating ( n = 4 ) women who did not use oral contraceptives ( P < 0.01 ) ; however , excretion rose ( P < 0.05 ) by 3 mo postpartum . In the nonlactating and never pregnant groups , women using oral contraceptives excreted less urinary calcium than the other women ( P < 0.01 ) . Lactating women excreted less urinary zinc ( 1 - 6 mo ) than did control and non-lactating women ( P < 0.01 ) . Mechanisms may possibly be operating during lactation that depress urinary calcium for > or = 2 mo and urinary zinc < or = 6 mo postpartum To estimate the effect of maternal zinc deficiency on pregnancy outcomes , we conducted a zinc supplementation trial in an urban shantytown in Lima , Peru , a population with habitual low zinc intakes . Beginning at 10 - 24 wk gestation , 1295 mothers were r and omly assigned to receive prenatal supplements containing 60 mg iron and 250 ( g folate , with or without 15 mg zinc . Women were followed up monthly during pregnancy . At birth , newborn weight was recorded , and crownheel length , head circumference and other circumferences and skinfold thicknesses were assessed on d 1 . At delivery , 1016 remained in the study ;  duration of pregnancy  was known for all women , and birth weight information was available for 957 newborns . No differences were noted in duration of pregnancy ( 39.4 + /- 2.2 vs. 39 . 5 + /- 2.0 wk ) or birth weight ( 3267 + /- 461 vs. 3300 + /- 498 g ) by prenatal supplement type ( iron + folate + zinc vs. iron + folate ; P > 0.05 ) , and there were no differences in the rates of preterm ( < 37 wk ) or post-term ( > 42 wk ) delivery , low birth weight ( < 2500 g ) or high birth weight ( > 4000 g ) . Finally , there were no differences by prenatal supplement type in newborn head circumference , crownheel length , chest circumference , mid-upper arm circumference , calf circumference or skinfold thickness at any of three sites . Adjustment for covariates and confounding factors did not alter these results . Adding zinc to prenatal iron and folate tablets did not affect duration of pregnancy or size at birth in this population BACKGROUND Maternal zinc deficiency during pregnancy may be widespread among women in developing countries , but few data are available on whether prenatal zinc supplementation improves maternal and neonatal zinc status . OBJECTIVE We studied whether maternal zinc supplementation improved the zinc status of mothers and neonates participating in a supplementation trial in a shantytown in Lima , Peru . DESIGN Beginning at gestation week 10 - 24 , 1295 mothers were r and omly assigned to receive prenatal supplements containing 60 mg Fe and 250 microg folate , with or without 15 mg Zn .  Venous blood and urine sample s were collected at enrollment , at gestation week 28 - 30 , and at gestation week 37 - 38 . At birth , a sample of cord vein blood was collected . We measured serum zinc concentrations in 538 women , urinary zinc concentrations in 521 women , and cord zinc concentrations in 252 neonates . RESULTS At 28 - 30 and 37 - 38 wk , mothers receiving zinc supplements had higher serum zinc concentrations than mothers who did not receive zinc ( 8.8 + /- 1.9 compared with 8.4 + /- 1.5 micromol/L and 8.6 + /- 1.5 compared with 8.3 + /- 1.4 micromol/L , respectively ) . Urinary zinc concentrations were also higher in mothers who received supplemental zinc ( P < 0.05 ) . After adjustment for covariates and confounding factors , neonates of mothers receiving zinc supplements had higher cord zinc concentrations than neonates of mothers who did not receive zinc ( 12.7 + /- 2.3 compared with 12.1 + /- 2.1 micromol/L ) . Despite supplementation , maternal and neonatal zinc concentrations remained lower than values reported for well-nourished population s. CONCLUSION Adding zinc to prenatal iron and folate tablets improved maternal and neonatal zinc status , but higher doses of zinc are likely needed to further improve maternal and neonatal zinc status in this population BACKGROUND Little is known about how maternal zinc intake influences growth in utero and in postnatal life in humans . OBJECTIVE We aim ed to assess the effect of maternal zinc supplementation during pregnancy on infant growth through age 1 y. DESIGN A double-blind , r and omized controlled trial of prenatal zinc supplementation was conducted from 1995 to 1997 in Lima , Peru . Women ( n = 1295 ) were enrolled at 15.6 + /- 4.6 wk gestation and assigned to receive daily supplements with zinc ( 15 mg Zn + 60 mg Fe + 250 microg folic acid ) or without zinc ( 60 Fe + 250 microg folic acid ) through pregnancy to 1 mo after delivery . At birth , 546 infants were followed for 12 mo to assess growth . Anthropometric measures of body size and composition were collected monthly , and morbidity and dietary intake surveillance was carried out weekly . RESULTS No differences in maternal socioeconomic characteristics by treatment group or follow-up period were found . Infants born to mothers prenatally supplemented with zinc had significantly ( P < 0.05 ) larger average growth measures beginning in month 4 and continuing through month 12 . In longitudinal regression modeling , prenatal zinc was associated with greater weight ( by 0.58 + /- 0.12 kg ; P < 0.001 ) , calf circumference ( by 1.01 + /- 0.21 cm ; P < 0.001 ) , chest circumference ( by 0.60 + /- 0.20 cm ; P = 0.002 ) , and calf muscle area ( by 35.78 + /- 14.75 mm(2 ) ; P = 0.01 ) after adjustment for a range of covariates . No effect was observed for linear growth . CONCLUSION Maternal zinc supplementation in this population was associated with offspring growth , which is suggestive of lean tissue mass accretion BACKGROUND There is a major increase in endogenous zinc excretion , specifically via the mammary gl and , in early human lactation . Whereas fractional absorption of dietary zinc has been reported to increase in early human lactation , it is not known to what extent adaptive mechanisms may maintain zinc homeostasis , especially when dietary zinc intake is relatively low . OBJECTIVE The objective of this study was to quantitate major variables of zinc homeostasis during early lactation in subjects from a population whose habitual dietary zinc intake is low . DESIGN We studied 18 free-living lactating women from a rural community of northeast China whose infants were exclusively breast-fed .  The subjects were studied at approximately 2 mo of lactation with use of stable isotopes of zinc and metabolic collection techniques .  Milk volume was measured with use of a deuterium enrichment method . RESULTS The mean ( + /-SD ) secretion of zinc in milk was 2.01 + /- 0.97 mg/d , the intake of zinc was 7.64 + /- 1.61 mg/d , and the fractional absorption of zinc was 0.53 + /- 0.09 , for a total daily zinc absorption of 4.00 + /- 0.71 mg/d . Endogenous zinc excretion in urine and feces was 0.30 + /- 0.10 and 1.66 + /- 0.97 mg/d , respectively . CONCLUSIONS Zinc balance , including zinc secreted in breast milk , was maintained at approximately 2 mo of lactation in women whose habitual diet was low in zinc . Homeostasis was achieved by high fractional absorption of zinc and intestinal conservation of endogenous fecal zinc Dietary zinc ( Zn ) intake and selected biochemical indices of Zn status were studied longitudinally at monthly intervals in 46 pregnant middle-income women , 10 of whom received a daily supplement of 15 mg Zn .  Mean dietary Zn intake for the nonsupplemented subjects ( group A ) was 11.3 + /- 4.1 mg/day ( 56 % of the Recommended Dietary Allowances ) , and for the Zn-supplemented subjects ( group B ) was 21.7 mg/day ( 109 % of the Recommended Dietary Allowance ) , including an average intake of 11.1 mg/day as supplemental Zn . The mean plasma Zn concentration of group A at 2 months gestation , 71.4 + /- 9.8 micrograms/dl , was 17 % lower than that of nonpregnant control women , and continued to decline significantly ( p less than 0.01 ) between 2 and 10 months gestation . Plasma Zn of group B did not differ significantly from group A at any stage of gestation . Mean serum alkaline phosphatase activity of group B was higher than that of group A at 7 of 8 months studied ( p less than 0.05 ) . The level of prenatal iron supplementation  in group A was negatively correlated with alkaline phosphatase activity and plasma Zn in the 2nd and 3rd trimesters , respectively . It is concluded that an early and progressive decline in plasma Zn which is not influenced by Zn intake occurs during gestation . Tentative st and ards for lower limits of normal at monthly intervals have been suggested . The higher alkaline phosphatase activity of group B compared with group A suggested that the dietary Zn intake of the latter was suboptimal . Prenatal supplemental iron may adversely affect maternal Zn status Forty lactating women were r and omly assigned to four treatment groups . Beginning at 1-d postpartum the women in each group received a daily vitamin-mineral supplement for 9 mo . The treatments differed only in the amount of vitamin B-6 ( 0.5 or 4.0 mg pyridoxine ) and zinc ( 0 or 25 mg ) included in the supplements . The 4.0-mg pyridoxine supplements significantly increased plasma total vitamin B-6 , plasma pyridoxal phosphate ( PLP ) , and milk total vitamin B-6 , thus showing that maternal intake exerts a significant effect on vitamin B-6 concentration in milk . There was no effect of vitamin B-6 intake on plasma , erythrocyte , or milk zinc concentration . The 25-mg zinc supplement also had no effect on plasma , erythrocyte , or milk zinc concentration , suggesting that maternal zinc intake is not a major regulator of milk zinc concentration We studied zinc nutrition in exclusively breast-fed infants whose growth deviated from the norm . Their number fell from 200 at birth to 116 at the age of 6 months and 36 at the age of 9 months . The mothers received 0 , 20 , or 40 mg Zn+ + as sulfate daily . Breast milk intake and concentrations of zinc in milk as well as in maternal and infant serum were measured . Individual zinc concentrations in milk showed channeling . The 20-mg supplement had no effect on the parameters measured . In contrast , 40 mg increased the maternal serum zinc concentration by 2 months and slowed the normal decline of milk zinc concentration by 6 months . Maternal supplementation had no effect on infant serum concen-trations ; they remained lower than adult levels throughout the 1st year of life .  Zinc intake was low ( about one-tenth of RDA ) , but it seemed to be adequate ; the serum concentrations of the infants were stable after the age of 2 months . Low zinc concentrations in serum were not associated with impaired growth . On the contrary , the infants with the highest rates of growth had the lowest zinc concentrations . The infant serum zinc concentrations were channeled , but they were also influenced by the zinc intake . Reference values for breast-fed infants are given OBJECTIVE To evaluate whether zinc supplementation during pregnancy is associated with an increase in birth weight . DESIGN A r and omized double-blind placebo-controlled trial . SETTING Outpatient clinic and delivery service at the University of Alabama at Birmingham . PATIENTS Five hundred eighty medically indigent but otherwise healthy African-American pregnant women with plasma zinc levels below the median at enrollment in prenatal care , r and omized at 19 weeks ' gestational age . Women were subdivided by the population median body mass index of 26 kg/m2 into two groups for additional analyses . INTERVENTION Women who were taking a non-zinc-containing prenatal multivitamin/mineral tablet  were r and omized to receive either a daily dose of 25 mg of zinc or a placebo until delivery . MAIN OUTCOME MEASURES Birth weight , gestational age at birth , and head circumference at birth . RESULTS In all women , infants in the zinc supplement group had a significantly greater birth weight ( 126 g , P = .03 ) and head circumference ( 0.4 cm , P = .02 ) than infants in the placebo group . In women with a body mass index less than 26 kg/m2 , zinc supplementation was associated with a 248-g higher infant birth weight ( P = .005 ) and a 0.7-cm larger infant head circumference ( P = .007 ) . Plasma zinc concentrations were significantly higher in the zinc supplement group . CONCLUSIONS Daily zinc supplementation in women with relatively low plasma zinc concentrations in early pregnancy is associated with greater infant birth weights and head circumferences , with the effect occurring predominantly in women with a body mass index less than 26 kg/m2 Women in different trimesters of pregnancy ( Group B ; n = 106 ) were administered 200 mg zinc sulphate ( elemental Zn 45 mg ) orally/day from the day of reporting till delivery . Untreated group of 62 served as control . Levels of zinc in maternal serum , umbilical cord blood serum , and urine were estimated . Pregnancy outcome was assessed in terms of incidence of prematurity , IUGR , birth weight ; apgar score and gestational age . Serum zinc levels in Gp . A declined significantly from 113.00 + /- 2.80 ug/dl in I trimester to 83.78 + /- 2.20 ug/dl in III ( P < 0.001 ) . Following zinc supplementation ( Gp . B ) serum zinc levels increased significantly from 109.70 + 3.23 micrograms/dl to 205.40 + /- 4.47 micrograms/dl ( P < 0.001 ) . Urinary excretion of zinc in Gp . A declined significantly with increase in the period of gestation . However in Gp . B , elimination of Zn increased significantly in proportion with the serum levels ( P < 0.001 ) cord blood serum zinc level was normal irrespective of maternal serum Zn levels . Following oral Zn supplementation , levels increased significantly from below 127.0 micrograms/dl to above 158.0 micrograms/dl in Gp . B ( P < 0.001 ) . Maternal serum and cord blood serum zinc ratios were fairly constant in Gp . A as well as in Gp . B. Birth weight of babies born with Zn supplementation was significantly higher than control and was related to duration of oral zinc supplementation ( P < 0.001 ) . Gestational age of babies in Gp . B was significantly higher than respective controls when Zn supplementation was given for more than 3 months ( P < 0.01 ) , and was related to duration of zinc therapy ( P < 0.05 ) . ( ABSTRACT TRUNCATED AT 250 WORDS Effects of stage of lactation , nutrient intake , and cultural differences on the composition of human milk were examined during the first 6 mo of lactation in American and Egyptian women . In both population groups zinc levels in milk decreased from 1 to 6 months of lactation . American women supplemented with Zn had higher levels of Zn in their milk than did unsupplemented American or Egyptian women . Concentrations of calcium and magnesium were not significantly different in milk of American and Egyptian women except at month 6 of lactation . Ca levels in milk of both population groups increased from 1 to 2 - 3 mo of lactation and then decreased at 6 mo ; Mg concentrations increased from 1 to 3 mo and then reached a plateau . Similarities in the longitudinal decrease observed in Zn levels of milk in Zn supplemented and unsupplemented subjects suggested physiological regulation The effects of a zinc supplement on maternal zinc status and milk zinc concentrations through > or = 7 mo of lactation were examined . Seventy-one lactating women received either a daily 15-mg zinc supplement ( ZS , n = 40 ) or placebo ( NZS , n = 31 ) started by 2 wk postpartum in a double-blind , r and omized design . Overall mean zinc intakes were 13.0 + /- 3.4 mg/d for the NZS group and 25.7 + /- 3.9 mg/d ( including supplement ) for the ZS group . Plasma zinc concentrations of the ZS group were significantly higher than those of the NZS group ( P = 0.05 ) . Milk zinc concentrations declined significantly over the course of the study for all subjects but were not affected by zinc supplementation . The mean dietary zinc intake observed in the nonsupplemented group was adequate to maintain normal maternal zinc status and milk zinc concentrations through > or = 7 mo lactation . Similar controlled intervention trials in less well-nourished population s will be required to assess the impact of lower zinc intakes on milk zinc concentrations
target: We hypothesize , therefore , that zinc homeostatic adjustments during pregnancy and lactation improve zinc utilization sufficiently to provide the increased zinc needs in these stages and , therefore , mitigate immediate detrimental effects due to a low zinc intake .
background: Zinc plays critical roles during embryogenesis , fetal growth , and milk secretion , which increase the zinc need for pregnancy and lactation .
  Increased needs can be met by increasing the dietary zinc intake , along with making homeostatic adjustments in zinc utilization .
  Potential homeostatic adjustments include changes in circulating zinc , increased zinc absorption , decreased zinc losses , and changes in whole body zinc kinetics .
  Although severe zinc deficiency during pregnancy has devastating effects , systematic review s and meta- analysis of the effect of maternal zinc supplementation on pregnancy outcomes have consistently shown a limited benefit .
  The specific questions addressed are the following : How is zinc utilization altered during pregnancy and lactation ?
  Are those homeostatic adjustments influenced by maternal zinc status , dietary zinc , or zinc supplementation ?