https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(13)60937-X.pdf

Maternal and child undernutrition and overweight in low-income and middle-income countries

Chapter 1: Overview of Zinc Nutrition ............................................................................................................... S99 1.1 Biological functions of zinc ............................................................................................................................. S99 1.2 Tissue zinc distribution and reserves .............................................................................................................. S99 1.3 Zinc metabolism ........................................................................................................................................... S100 1.4 Importance of zinc for human health........................................................................................................... S101 1.5 Human zinc requirements............................................................................................................................. S105 1.5.1 Adult men ............................................................................................................................................. S106 1.5.2 Adult women......................................................................................................................................... S109 1.5.3 Children ................................................................................................................................................ S110 1.5.4 Pregnancy.............................................................................................................................................. S111 1.5.5 Lactation ............................................................................................................................................... S112 1.6 Dietary sources of zinc and suggested revisions of Recommended Daily Intakes .................................... S112 1.6.1 Dietary sources of zinc and factors affecting the proportion of zinc available for absorption ........ S112 1.6.2 Revised estimates of dietary requirements and recommended intakes for zinc ............................... S114 1.7 Zinc toxicity.................................................................................................................................................... S118 1.8 Causes of zinc deficiency and groups at high risk ....................................................................................... S121 1.9 Summary ........................................................................................................................................................ S123

International Zinc Nutrition Consultative Group (IZiNCG) technical document #1. Assessment of the risk of zinc deficiency in populations and options for its control.

Zinc requirements and the risks and benefits of zinc supplementation

Serum vitamin D concentrations among elderly people in Europe

Preterm birth, which occurs in 11 percent of all pregnancies, is responsible for the majority of neonatal deaths and nearly one half of all cases of congenital neurologic disability, including cerebral palsy.1 Although all births before 37 weeks of gestation are considered premature, births before 32 weeks' gestation (2 percent of all births) account for most neonatal deaths and disorders.2 State and national vital statistics indicate that the incidence of preterm birth has risen over the past 15 years (Figure 1), and it remains twice as high among black women as among white women.3–5 Preterm birth is commonly categorized . . .

https://www.nejm.org/doi/pdf/10.1056/NEJM199807303390506

Prevention of premature birth.

The levels of zinc in plasma, erythrocytes, polymorphonuclear (PMN) and mononuclear (MN) white cells were measured after delivery in women giving birth to appropriate-for-gestational-age (AGA) babies (group I mothers), or small-for-gestational-age (SGA) babies (group II mothers) and in non-pregnant controls. Mean maternal plasma zinc and albumin levels 24-48 h after delivery were lower than in controls, but PMN and MN zinc levels were unchanged. PMN zinc levels were lower than those of MN cells. PMN and MN zinc levels were significantly lower in group II mothers than in group I, irrespective of smoking habits. There were no racial differences in peripheral white cell zinc levels. PMN, and to a lesser degree MN, zinc levels were lower in smoking than in non-smoking mothers. Erythrocyte zinc did not correlate with other zinc measurements nor with the size of the babies. Fetal erythrocyte zinc levels were one-third of maternal levels. A combination of smoking and/or low PMN zinc levels selects 85% of mothers having small-for-gestational-age babies.

Maternal zinc and intrauterine growth retardation

Are iron-folate supplements harmful?

A double-blind randomised trial of oral zinc supplementation was carried out during the last two trimesters of pregnancy. Fifty-six women at risk of delivering a small-for-gestational-age baby received either zinc supplement (22.5 mg daily) or placebo. Twenty-nine of the women were compliant. Zinc significantly reduced the incidence of intrauterine growth retardation, and most measured indices of labour and fetal health were better in the supplemented group. Larger studies are now needed to confirm a role for selective zinc supplementation in at-risk pregnancies.

A double-blind trial of zinc supplementation in pregnancy.

The growing fetus and infant are at risk of becoming deficient of zinc, an adequate supply of which is essential for normal growth and development. Mild maternal zinc depletion was strongly associated with intrauterine growth retardation. Low levels of zinc in maternal plasma and poor placental perfusion reduced the materno-fetal transfer of zinc. Mean maternal dietary intake of zinc was 60% recommended daily allowance and mothers of small-for-gestational-age (SGA) babies consumed significantly less zinc than mothers of appropriate-for-gestational-age babies. In addition, iron/folate supplements, which are often routinely prescribed during pregnancy, despite dietary intakes of iron and folate being adequate, significantly decreased the oral bio-availability of zinc in pregnant women. Zinc supplementation may be beneficial to women at risk of delivering SGA babies. Zinc requirements and interactions are also important to consider when designing mineral supplements for preterm babies, infant formulae and food fortification in developing countries.

Karen Simmer

Papers

Maternal zinc and intrauterine growth retardation

Are iron-folate supplements harmful?

A double-blind trial of zinc supplementation in pregnancy.

Zinc in the Fetus and Newborn

Nutritional rehabilitation in Bangladesh--the importance of zinc.