Nutrient Requirements

L H Allen, University of California at Davis, Davis, CA,

© 2005 Elsevier Ltd. All rights reserved.

Providing pregnant women with their nutrient needs is a public health priority in both wealthier and poorer countries, although the local resources to attain this objective may vary widely. The inability to meet nutrient requirements during pregnancy can have serious and often long-term adverse effects on development during the fetal and postpartum period and on maternal health. Most of the research that provides information on nutrient requirements during pregnancy has been conducted in industrialized countries, although trials in developing countries have been important in revealing the adverse effects of maternal nutrition and the benefits of nutrient interventions. In general, even in wealthier countries there is an unacceptably high rate of pregnancy complications that may be prevented by improved maternal nutrition, including anemia, low birth weight, birth defects, and preeclampsia. The situation is far worse in poorer regions of the world, however.

The most recent and best described recommended intakes of nutrients during pregnancy are those of the Institute of Medicine, developed for the United States and Canada, and these are the main set presented in this article (Table 1). The recommendations for the United Kingdom were published in

1992 and are discussed here when recommendations differ substantially from those of the Institute of Medicine. Many other countries have their own sets of recommendations, as do organizations such as the Food and Agriculture Organization/World Health Organization and the European Economic Community.

The set of Dietary Reference Intake (DRI) recommendations developed by the Institute of Medicine includes several values. The Estimated Average Requirement (EAR) is the intake required to meet the nutrient needs of 50% of a population group (e.g., pregnant women). It is an important value for two reasons. First, it is the value used to estimate the prevalence of inadequate intakes of a nutrient in a population group; the percentage of a group consuming less than the EAR of a nutrient is the percentage with an inadequate intake. For energy, the Estimated Energy Requirement is equivalent to the EAR. Second, the Recommended Dietary Allowance (RDA) is calculated by adding two standard deviations (usually unknown but assumed to be 20%) to the EAR. The RDA should meet the requirements of 97.5% of a population group. The Tolerable Upper Level (UL) for a nutrient is the intake above which there is a risk of adverse effects.

Table 1 shows the RDA for nonpregnant women and the EAR, RDA, and UL for pregnant women.

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