Effect of high-dose iron supplements on fractional zinc absorption and status in pregnant women

Abstract

Background:Women have an increased risk of iron deficiency during pregnancy because of the demands of the developing fetus. Iron supplements are commonly advocated as a prophylactic treatment and are generally taken with meals to reduce side effects, but iron can interfere with the absorption of zinc. Objective: The aim was to determine the effect of consuming an iron supplement (100 mg Fe/d as ferrous gluconate) with meals from 16 wk gestation to term on zinc status and absorption. Design: Stable-isotope techniques were used to measure zinc status (exchangeable zinc pool, EZP) and fractional zinc absorption (FZA) in early and late pregnancy from a meal consumed at a different time from that of iron supplement or placebo consumption in 6 women given iron supplements and 7 given a placebo. Results: FZA increased during pregnancy, independent of iron supplementation. FZA was significantly higher (P 0.001) at week 34 than at weeks 16 and 24, and urinary zinc excretion was higher at week 34 than at week 16 (P ҃ 0.02). The size of the EZP remained unchanged throughout pregnancy and was unaffected by iron supplementation. The iron status of iron-supplemented women was higher than that of the placebo group. Conclusions: In iron-replete pregnant women who consumed a Western diet, no detectable adverse effects on zinc metabolism were observed after ingestion of 100 mg Fe/d. An increase in the efficiency of zinc absorption was observed during late pregnancy.Am J Clin Nutr 2007;85:131-6.

Scientific Opinion on Dietary Reference Values for zinc

“…In pregnancy and, notably, in early lactation, up-regulation of zinc absorption has been reported (Fung et al, 1997;Harvey et al, 2007;Donangelo and King, 2012). For example, in two longitudinal studies of zinc homeostasis during pregnancy and lactation, FAZ increased 1.3-fold (p > 0.05) from preconception to late pregnancy in 13 US women with a zinc intake of about 12 mg/day (Fung et al, 1997) and 1.5-fold (p < 0.05) from early (10-12 weeks) to late (34-36 weeks) pregnancy in 10 Brazilian women ingesting about 9 mg/day (Donangelo et al, 2005).…”

Carnitine status of pregnant women: effect of carnitine supplementation and correlation between iron status and plasma carnitine concentration

“…Epidemiologic studies have disclosed that fertile, non-pregnant women, often have a low iron status (Milman, 2006). Pregnant women have even a particular high risk of iron deficiency because of the high iron demands of the developing fetus (Harvey et al, 2007). Owing to the requirement of iron for carnitine biosynthesis, we hypothesized that an inadequate iron status could lead to a reduced endogenous carnitine biosynthesis in pregnant women, which could be an explanation for the low plasma carnitine concentrations.…”

Impact of twice weekly versus daily iron supplementation during pregnancy on maternal and fetal haematological indices: a randomized clinical trial

“…Several studies indicate that iron absorption could improve if iron supplements were administered intermittently, matched with mucosal regeneration time of the intestine, which in turn diminishes sideeffects and enhances compliance rates [1,6]. Interaction of iron with other micronutrients especially zinc, and also the postulated relationship between high-dose iron supplementation and pregnancy complications such as gestational diabetes, preterm labour and low birth weight, suggest that the amount of iron recommended in the current protocol is too high [3,[7][8][9][10]. A number of researchers propose that weekly iron supplementation is a reasonable alternative to daily supplementation in terms of haematological indices as well as side-effects [2,6,10,11].…”