Zinc absorption and kinetics during pregnancy and lactation in Brazilian women. The relationship between maternal dietary intake and infant birthweight. Dietary supplements for the lactating mother: influence on the trace element content of milk Zinc supplementation during lactation: effects on maternal status and milk zinc concentrations. Zinc homeostasis during lactation in a population with a low zinc intake. Maternal zinc supplementation and growth in Peruvian infants. Plasma and erythrocyte zinc concentrations and their relationship to dietary zinc intake and zinc supplementation during pregnancy in low-income African-American women. Prenatal iron supplements impair zinc absorption in pregnant Peruvian women. Adding zinc to prenatal iron and folate supplements improves maternal and neonatal zinc status in a Peruvian population. Zinc status and dietary intake of pregnant women, Alexandria, Egypt. Maternal zinc supplementation does not affect size at birth or pregnancy duration in Peru. Zinc supplementation during pregnancy: zinc concentration of serum and hair from low-income women of Mexican descent. Maternal zinc during oral iron supplementation in pregnancy: a preliminary study. The impact of prenatal vitamin A and zinc supplementation on birth size and neonatal survival - a double-blind, randomized controlled trial in a rural area of Indonesia.
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 BACKGROUND Zinc and folate are important for fetal growth . However , the relationship between the dietary intake of these nutrients and pregnancy outcome is not settled . METHODS A prospect i ve study was conducted to ascertain the relationship between  maternal dietary zinc and folate intake  ( n = 1398 ) , serum zinc and folate levels ( n = 289 ) , and infant birthweight .  Twenty-four hour recalls were used to measure energy , zinc , folate and other nutrient intakes at 18 and 30 weeks of gestation . Subjects in the study were offered daily folic acid ( 1.0 mg ) and iron ( 60 mg as ferrous sulfate ) at enrollment . RESULTS Maternal zinc nutriture as assessed by serum and dietary intake was not associated with birthweight or length of gestation . There was a small but significant positive association between maternal folate intake and adjusted infant birthweight ( beta = 0.05 , p = 0.03 ) . The indirect measures of maternal nutritional status including maternal pre-pregnancy weight ( beta = 8.0 , p = 0.0001 ) and weight gain during pregnancy ( beta = 18.1 , p = 0.0001 ) were stronger predictors of adjusted infant birthweight as compared to energy intake and intake of zinc and folate . An increase of 320 , 290 , and 48 g in infant birthweight was associated with the 90th-10th percentile difference for pre-pregnancy weight , weight gain during pregnancy , and folate intake respectively . CONCLUSION These results indicate that pre-pregnancy weight and weight gain during pregnancy are both strong predictors of infant birthweight .  Folate intake , although significantly associated with birthweight , was a weak predictor while maternal intake of zinc and other nutrients was not associated with birthweight Milk production is a complex process where nutritional factors interact with structural hormonal and behavioural influences . In recent years important advances have been made in underst and ing the role of the nutritional status of lactating women on the outcome of breastfeeding . Many questions remain unanswered about the exact requirement of trace elements for lactating mothers . The effect of dietary zinc , copper and iodine supplements on the milk concentration of these micronutrients was studied . The supplementation trial employed a specific balanced nutritional supplement prepared for the nursing mothers . The study was carried out on women living in Ferrara and its surrounding area . The population under study was healthy Italian mothers , of good socioeconomic status , and their normal infants . In total , 32 women were enrolled in the study and 22 completed it . The infants ( 9F , 13 M ) were full‐term , healthy singletons and were put to breast within 12 h of birth . All women who finished the study completed a 3 d dietary record . Nutrient analysis revealed the following mean daily dietary trace element intake in the lactating mothers : zinc = 12 mg , copper = 1.4 mg and iodine = 145 μg . The zinc and copper dietary intake was in agreement with the daily intake proposed for nursing Italian mothers , while the daily intake of iodine was below the recommended intake of 200 μg . The breastfeeding mothers were placed in 2 groups , with 7 primiparas and 4 multiparas per group : lactating women eating a traditional Italian diet without vitamin and mineral supplements  , and lactating women enrolled in the nutrification programme  and given a nutritional supplement to their traditional diet . The supplement ( PerMamma Abbott ) provided 20 mg zinc sulfate , 2 mg copper sulfate and 116 μg potassium iodide . These quantities cover about 60‐90 % of the recommended intake for nursing Italian mothers . Sample s of 10 ml of milk were collected at 3 , 30 , 90 d postpartum . Zinc milk concentrations declined significantly over the study period for all lactating subjects , without differences in the rate of decline between the women who started supplementation during lactation and those who did not . Copper did not change during the first month of lactation , then declined at day 90 in supplemented and unsupplemented women , without significant differences between the two groups . An early sharp decline in milk iodine occurred in all lactating subjects , independently of iodine supplementation . After the first month of lactation breast milk iodide levels remained stable in all subjects under study . No significant differences between the two study groups were observed . The lack of correlation between the iodide level in breast milk and maternal dietary intake of iodine is not in agreement with previously published reports . The present results indicate that in healthy , well‐nourished lactating Italian women , whose diet is adequate , the levels of zinc , copper and iodine in milk are not influenced by short‐term supplementary intakes and that the milk levels of the trace elements studied are maintained over different levels of intake . Further research and examination by longitudinal studies are needed to establish the exact relationship between the amount of iodine furnished to the nursing mother and the iodine content of human milk . The role of compensatory homeostatic mechanisms which act during lactation needs further consideration and closer scrutiny 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 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 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 OBJECTIVE To evaluate the effects of usual dietary intake of zinc and of zinc supplementation during pregnancy on plasma and erythrocyte zinc concentrations . DESIGN A r and omized , double-blind , placebo-controlled trial . SUBJECTS Low-income African-American women ( n = 580 ) assigned r and omly to groups at 19 weeks of gestation . INTERVENTION A daily dose of zinc ( 25 mg ) or a placebo until delivery . MAIN OUTCOME MEASURES Plasma , erythrocyte , and dietary zinc levels . STATISTICAL ANALYSES Multiple regression and repeated measures analysis of variance . RESULTS In both the placebo and the supplemented groups , when all subjects were grouped by usual dietary zinc intake above or below the median ( 12 mg/day ) , results were the same : Women with high dietary zinc intake had higher erythrocyte zinc levels at the time of r and omization and at all subsequent measurements during pregnancy than those who had low dietary zinc intake ( P < or = .06 ; difference not significant for zinc-supplemented group ) ; no difference was observed for plasma zinc levels . On the other h and , when the subjects were stratified at the median by total daily zinc intake ( usual dietary zinc + 25 mg zinc supplement ) during pregnancy , a significant difference in plasma zinc levels ( P < .005 ) was found between women with high total zinc intake ( mean = 38 mg/day ) and low total intake ( mean = 13 mg/day ) at 26 , 32 , and 38 weeks of gestation ; however , no such differences were found in erythrocyte zinc levels . APPLICATIONS These results should help dietitians and other health professionals better underst and the expected changes in plasma and erythrocyte zinc levels during pregnancy , and the relationship between dietary and supplemental zinc and zinc nutriture 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 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 AND OBJECTIVES Deficiencies of protein , energy , and micronutrients are highly prevalent in developing countries and have major effects on pregnancy outcome . Low dietary intake is the most common reason for zinc deficiency . The present research is part of a larger double-blind r and omized-controlled trial to evaluate the effect of zinc supplementation on the pregnancy outcome . The aim of the present study was to assess the  zinc status and dietary intake of zinc and other macronutrients and micronutrients among pregnant women in Alex and ria , Egypt . PARTICIPANTS AND METHODS Participants were pregnant women attending two antenatal care centers that serve low-income and middle-income pregnant population s. A total of 1055 healthy pregnant women aged 20 - 45 years were assessed for eligibility . Of these , only 675 had serum zinc level below the median for the gestational age . They were assigned r and omly to one of three parallel groups . Zinc supplements were provided from 16 weeks until delivery . A sub sample of 100 women was assessed for their dietary intake . A question naire interview was used to collect basic socioeconomic and data on current pregnancy and labor . Dietary data were collected using the 24-h recall method and a food frequency question naire . The nutritive value of the daily diet was computed using the Egyptian food composition tables . The blood hemoglobin level , serum zinc level , and fasting blood sugar were determined . RESULTS Zinc deficiency was detected among 53.5 % of the sample . Dietary intake of zinc was low , representing 59.4 , 59.4 , and 62 % of the recommended dietary allowance ( RDA ) for the zinc group , zinc plus multivitamins , and the placebo group , respectively . The iron intake was below 50 % of the RDA . Protein intake was less than 70 % of the RDA . The mean intakes of fat were 191.97 , 211.8 , and 196.3 g/day for the three groups . The mean energy intake represented 51.1 , 53.5 , and 49.8 % of the RDA . CONCLUSION AND RECOMMENDATIONS Except for carbohydrate intake , the dietary intake of all macronutrients and micronutrients was low . The lowest intake was of iron ( below 50 % of the RDA ) . Zinc and protein intake represented less than 70 % of the RDA . The overall energy intake was around 50 % of the RDA . Nutritional health education should be used as a preventive approach to allow the large sector of the low-income population to maximize the use of the limited re sources in the best way . In women at high risk of zinc deficiency , zinc supplementation should be added to the routine supplements 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 The effect of zinc supplementation on concentrations of zinc in hair and serum of 213 pregnant Hispanic women attending a clinic in Los Angeles was assessed using a r and om , double-blind experiment . Both the treatment ( T ) and control ( C ) groups received similar vitamin and mineral supplements except that 20 mg zinc was added to the supplements for the treatment group . Nutrient intakes were calculated from 24-h recalls . The initial mean dietary  zinc intake of both groups was about 50 % of the Recommended Dietary Allowance ( 9 + /- 5 mg ) . Initially there were no significant differences between the two groups in mean zinc levels in serum ( 66 + /- 11 micrograms/dl , C , and 65 + /- 12 micrograms/dl , T ) or in hair ( 184 + /- 41 micrograms/g , C , and 175 + /- 38 micrograms/g , T ) . Zinc supplementation did not alter mean zinc levels in serum or hair but significantly ( p less than 0.05 ) reduced the number of low serum zinc values ( less than or equal to 53.3 micrograms/dl ) toward the end of pregnancy . Although serum zinc levels do decline in pregnancy , our results suggest that severely depressed levels ( less than or equal to 50 to 55 micrograms/dl ) indicate inadequate zinc status 1 . To investigate the possible effect of iron ingestion on maternal zinc status , one group of women was given 94 mg of iron per day as ferrous sulphate with multivitamins during the second and third trimesters of their pregnancies and another , control , group was given a placebo of multivitamins without iron . 2 . The subjects given iron developed significantly lower plasma zinc concentrations than those in the control group . This effect on zinc was maximal by 6 weeks , whilst that on maternal iron status was slower . 3 . There was no parallel decrease of zinc concentration in maternal mixed leucocytes , or of plasma heatlabile alkaline phosphatase activity , suggesting that there was a redistribution of zinc between plasma and tissues . 4 . The results indicate that iron supplementation during pregnancy alters the disposition of zinc in the mother BACKGROUND Prenatal supplementation with micronutrients may increase birth weight and thus improve infant health and survival in setting s where infants and children are at risk of micronutrient deficiencies . OBJECTIVE To assess whether vitamin A and /or zinc supplementation given during pregnancy can improve birth weight , birth length , neonatal morbidity , or infant mortality . METHODS A double-blind , r and omized controlled trial supplementing women ( n = 2173 ) in Central Java , Indonesia throughout pregnancy with vitamin A , zinc , combined vitamin A+zinc , or placebo . RESULTS Out of 2173 supplemented pregnant women , 1956 neonates could be evaluated . Overall , zinc supplementation improved birth length compared to placebo or combined vitamin A+zinc ( 48.8 vs. 48.5 cm , p = 0.04 ) ; vitamin A supplementation improved birth length compared to placebo or combined vitamin A+zinc ( 48.7 vs. 48.2 cm , p = 0.04 ) . These effects remained after adjusting for maternal height , pre-pregnancy weight , and parity . There was no effect of supplementation on birth weight , the proportion of low birth weight , neonatal morbidity , or mortality . CONCLUSIONS Prenatal zinc or vitamin A supplementation demonstrates a small but significant effect on birth length , but supplementation with zinc , vitamin A or a combination of zinc and vitamin A , have no effect on birth weight , neonatal morbidity , or mortality
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 .
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 ?