Nutrition During Pregnancy Part I: Weight Gain, Part II: Nutrient Supplements (1990) / Chapter Skim
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15 Trace Elements
15 Trace Elements
Pages 299-317
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From page 299... ...
Progressive physiologic changes during gestation contribute to the difficulty of interpreting laboratory data. Although mild deficiency of one or more trace elements may be one etiologic factor in a multifactorial problem such as premature delivery or intrauterine growth retardation, a causal role would be difficult to detect.
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From page 300... ...
In the rat, maternal dietary zinc restriction during embryogenesis has profound teratogenic effects involving many organ systems, especially the skeletal and central nervous systems (Dreosti, 1982; Hurley, 1981~. The pattern of malformations depends on the precise period of zinc deprivation and the embryonic events that are occurring at that stage of gestation
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From page 301... ...
The prevalence and consequences of milder zinc deficiency during human pregnancy remain poorly defined. In several studies, associations were found between low zinc levels in plasma or tissue and complications of pregnancy and delivery, such as pregnancy-induced hypertension; prolonged labor; intrapartum hemorrhage; and impaired fetal development such as congenital malformations, intrauterine growth retardation (Adeniyi, 1987; Crosby et al., 1977; Fehily et al., 1986)
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Zinc supplementation was, however, associated with a lower incidence of premature births in that study. Sample sizes have been inadequate to assess definitively the effect of zinc supplements on intrauterine growth.
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Dosage Range and Toxicity The level of zinc supplementation that is safe for pregnant women has not been clearly established. Doses used in zinc supplementation studies in pregnant women have ranged from 15 to 45 mg/day, but one unconfirmed report suggests an association between zinc supplements of 45 mg/day during pregnancy and premature delivery (Kumar, 1976~.
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From page 304... ...
Placental transport of zinc was disturbed by chronic alcohol ingestion and did not improve with maternal zinc supplementation in an animal model (Ghishan and Greene, 19834. In pregnant smokers, whose placental cadmium levels are high, the placental zinc-to-cadmium ratio is positively related to infant birth weight (Kuhnert et al., 1988~.
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From page 305... ...
does appear to depress plasma zinc in pregnant women and should, therefore, be avoided. Zinc supplementation is recommended when >30 mg of supplemental iron is administered per day.
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From page 306... ...
Usual Intakes Average copper intake by nonpregnant adults is approximately 1 mg/day (Holder et al., 1979; Pennington et al., 1989) and by pregnant women, 1.4 to 1.8 mg/day (see Table 13-2; Campbell, 1988~.
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From page 307... ...
There is a need for further substantiation of this effect, which has been reported only with very low copper intakes. Recommendations for Supplementation Although the estimated mean intake of copper is lower than the estimated copper requirements during the last trimester of pregnancy, there is no evidence that any pregnant woman is deficient in copper to the extent that normal fetal growth and development are jeopardized.
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From page 308... ...
that occurs in young children and women of childbearing age. Although the etiology of this disease is probably multifactorial, a severe dietary deficiency of selenium is the major etiologic factor (Keshan Disease Research Group, 1979a,b)
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From page 309... ...
in selenium-deficient patients maintained on prolonged total parenteral nutrition without selenium supplements (Johnson et al., 1981~. Milder selenium deficiency in parenterally fed children has been associated with macrocytosis and hair pigment changes (Vinton et al., 1987~.
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From page 310... ...
Usual intake by nonpregnant women aged 25 to 30 is approximately 2 mg/day (Pennington et al., 1989~. Both positive and negative manganese balances were observed during late pregnancy in women whose daily manganese intake averaged 2 to 7 mg (Armstrong, 1985~.
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From page 311... ...
Public health measures, including fluoridation of the community or school water supplies or oral supplementation, have been directed primarily toward infants and children younger than age 16. Adults may also derive some benefit from a fluoridated water supply or a 1-mg fluoride supplement per day (American Dental Association Council on Dental Therapeutics, 1984~.
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From page 312... ...
· There is no persuasive evidence that it is potentially beneficial to routinely supplement pregnant women with any trace element other than iron in the United States. · Although zinc nutrition during pregnancy has attracted recent professional and public interest, there is insufficient evidence to support a recommendation for routine prenatal zinc supplementation.
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Trace Elements in Human and Animal Nutrition, 5th ea., Vol.
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From page 314... ...
1983. Fetal alcohol syndrome: failure of zinc supplementation to reverse the effect of ethanol on placental transport of zinc.
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1984. Zinc supplementation during pregnancy: effects on selected blood constituents and on progress and outcome of pregnancy in low-income women of Mexican descent.
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Bremner, and J.K Chesters, eds. Trace Elements in Man and Animals 5.
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From page 317... ...
1983. Copper absorption and retention in pregnant women fed diets based on animal and plant proteins.
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