Nutrition During Pregnancy and Lactation Exploring New Evidence: Proceedings of a Workshop (2020) / Chapter Skim
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4 Iron, Vitamin D, Calcium, Antioxidants, and Iodine
4 Iron, Vitamin D, Calcium, Antioxidants, and Iodine
Pages 39-56
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From page 39... ...
O'Brien touched on current intake recommendations and intake levels, the need for -- and outcomes related to -- supplementation, and biomarkers related to these nutrients.
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From page 40... ...
. • Risk of iron deficiency during pregnancy is more common later in pregnancy, among women carrying multiples, among non-Hispanic blacks, and among pregnant adolescents, whereas risk of excessive iron status is more common among Asians and Pacific Islanders (O'Brien)
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From page 41... ...
A study found that the placenta can respond to low maternal iron status by upregulating iron uptake proteins (Young et al., 2010)
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From page 42... ...
In the United States, prenatal supplements contain 27 mg of iron, whereas Canadian prenatal supplements contain 16–20 mg of iron. O'Brien explained that the lower iron content of the Canadian supplements stems from an analysis of data from the Canadian Community Health Survey (Cockell et al., 2009)
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From page 43... ...
The studies used to establish the CDC anemia thresholds included primarily Caucasian participants who had iron intakes above current recommendations, which O'Brien underscored as further evidence that the data do not necessarily reflect the current circumstances. Only a small portion of anemia cases are classified as iron-deficiency anemia.
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From page 44... ...
Research Needs Related to Iron Despite evidence that iron supplementation improves hematological indicators, more research into the benefits and risks of supplementation is warranted, O'Brien said. In particular, she said that more work is needed to determine an optimal dose of iron supplementation during pregnancy, to evaluate current thresholds for hemoglobin and biomarker data that determine iron status, and to identify characteristics of at-risk populations (e.g., racial and ethnic differences)
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From page 45... ...
Calcium absorption increases during pregnancy to meet fetal calcium demands. Changes in calcium metabolism that occur during pregnancy and lactation do not appear to have a negative effect on long-term bone health.
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NUTRITIONAL ANTIOXIDANTS DURING PREGNANCY AND LACTATION Corrine Hanson, director and professor in the Medical Nutrition Education Division at the University of Nebraska Medical Center, acknowledged that the term antioxidants encompasses hundreds of compounds. Hanson, therefore, focused her remarks on the current state of the science on the relationship between women's intake and status of select dietary antioxidants and pregnancy and infant outcomes.
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From page 47... ...
Relationships between intakes of some of the dietary antioxidants and maternal and infant serum concentrations have been assessed. Infant serum carotenoid concentration is correlated with maternal intake, but it is only 5–15 percent of maternal serum concentration.
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From page 48... ...
Hanson raised the issue of participant antioxidant status for these trials, as serum concentrations were either not reported or indicated that the women were replete. Moving on to evidence on relationships with preeclampsia, Hanson reported that findings from observational studies are inconsistent and supplementation trials did not find an effect.
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From page 49... ...
IODINE IN PREGNANCY AND LACTATION "There have been huge shifts in our iodine intake in the last few decades," said Elizabeth Pearce, professor of medicine at the Boston University School of Medicine in the Section of Endocrinology, Diabetes, and Nutrition. To review the importance of the changing landscape of iodine nutrition and its relevance to pregnancy and lactation, Pearce discussed dietary iodine requirements and status assessment, the consequences of iodine deficiency or excess, current U.S.
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From page 50... ...
Pearce indicated that the higher iodine intake recommendations for lactating women have recently been called into question. Median urinary iodine excretion can be used to characterize p opulation-level iodine status.
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. IQ benefits as high as 12–13 points were reported in a study conducted in China that optimized maternal iodine status in populations with severe iodine deficiency.
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There are subgroup differences in urinary iodine excretion by age and sex. The group most at risk for low urinary iodine excretion are women of reproductive age, who are the population group most vulnerable to the effects of iodine deficiency, observed Pearce.
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From page 53... ...
Concerns over excessive iodine intakes grew in the 1980s, leading to federal limits on the iodine content of cattle feed. Pearce suggested that this change could possibly explain why urinary iodine excretions were elevated among participants in the first NHANES.
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From page 54... ...
O'Brien thought that pregnant and lactating women, whose diets are inherently more restrictive, could find ways to incorporate potential shortfall nutrients with the help of a dietitian. Reiterating a point made in her presentation, Hanson explained that for many of the antioxidant compounds, it is difficult to know what intakes are optimal because they do not have quantitative intake recommendations.
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From page 55... ...
Hanson said that antioxidant deficiency is not well characterized, except for the case of selenium for which there is evidence from developing countries where the selenium content of the soil is deficient. Implications of Low and High Iodine Intake In reflecting on Pearce's presentation, Dwyer wanted to know if there are data on the iodine status of Asian women, particularly those who migrated from areas in which the population has low iodine status.
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From page 56... ...
Pearce indicated that an entire generation or two of children were exposed to high iodine intakes. Data on the effects of such intakes are limited, noted Pearce, but she indicated that the prevalence of goiter in the United States did not change during this time.
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