Methyl donors, iodine, and DHA--is maternal supplementation beneficial? Introduction

Use of dietary supplements by pregnant and lactating women in North America

Nutrient requirements increase during periods of growth and development such as pregnancy and lactation. In response, many clinicians recommend dietary supplements during these important periods of the life cycle. Although there exist some recommendations concerning the need for a limited number of nutrients in supplemental form (eg, iron, folic acid, and iodine), there is a relative paucity of data concerning the use of dietary supplements during pregnancy and lactation. Limited data suggest, however, that usage is dependent on demographic, sociologic, and economic factors. Thus, it is possible that the nation's most at-risk populations may be those who are least likely to comply with these recommendations. As researchers continue to study what is meant by "optimal nutrition" during pregnancy and lactation, it is likely that additional recommendations concerning dietary supplements will emerge. For example, it is possible that increased consumption of some of the long-chain polyunsaturated fatty acids during pregnancy or lactation may impart a benefit to infant health. Understanding better the population dynamics related to supplement use during these periods will be critical in implementation of campaigns designed to encourage appropriate use--and discourage inappropriate use--of dietary supplements during these important phases of human reproduction. The purpose of this article is to briefly review what is known about the use of dietary supplements in North America and, more specifically, in pregnant and lactating women. In addition, information concerning barriers to supplement use is discussed as are current recommendations for dietary supplement consumption during these periods of the life cycle.

Iodine deficiency in pregnancy and the effects of maternal iodine supplementation on the offspring: a review

The World Health Organization (WHO) recently increased their recommended iodine intake during pregnancy from 200 to 250 microg/d and suggested that a median urinary iodine (UI) concentration of 150-249 microg/L indicates adequate iodine intake in pregnant women. Thyrotropin concentrations in blood collected from newborns 3-4 d after birth may be a sensitive indicator of even mild iodine deficiency during late pregnancy; a <3% frequency of thyrotropin values >5 mU/L indicates iodine sufficiency. New reference data and a simple collection system may facilitate use of the median UI concentration as an indicator of iodine status in newborns. In areas of severe iodine deficiency, maternal and fetal hypothyroxinemia can cause cretinism and adversely affect cognitive development in children; to prevent fetal damage, iodine should be given before or early in pregnancy. Whether mild-to-moderate maternal iodine deficiency produces more subtle changes in cognitive function in offspring is unclear; no controlled intervention studies have measured long-term clinical outcomes. Cross-sectional studies have, with few exceptions, reported impaired intellectual function and motor skills in children from iodine-deficient areas, but many of these studies were likely confounded by other factors that affect child development. In countries or regions where <90% of households are using iodized salt and the median UI concentration in school-age children is <100 microg/L, the WHO recommends iodine supplementation in pregnancy and infancy.

Docosahexaenoic acid supplementation in pregnancy and lactation

The goal of the Experimental Biology symposium on maternal supplementation was to review all available lines of evidence, delineate unanswered questions, and develop, if it seemed reasonable, a research agenda to determine whether maternal supplementation with specific nutrients might be beneficial. In the case of maternal docosahexaenoic acid (DHA) status, the topic addressed in this article, few clinical studies show benefits of maternal DHA supplementation during pregnancy or lactation for the infant or child. However, quite a large number of observational studies link higher intrauterine DHA exposure to a number of positive developmental outcomes. This article reviews the factors known to contribute to DHA status of women and their offspring during the reproductive cycle, relates maternal DHA status to that of the developing fetus and newborn, and reviews the evidence for functional differences in behavior related to DHA status, including the available evidence related to DHA supplementation of women pregnant and lactating and their offspring. Other outcomes for infants and children and for women themselves appear plausible and are also addressed as part of a research agenda for future work.

Is maternal diet supplementation beneficial? Optimal development of infant depends on mother's diet

There are periods during perinatal development in which specific nutrients are required for optimal development, and there is growing evidence that optimal dietary intake of these nutrients, which include iodine, docosahexaenoic acid, choline, and folate, is important. Lessons in how these nutrient effects were identified can help us to broaden our approaches for finding other critical nutrients: we are looking for nutrients for which there is a wide range of dietary intake, that have no or marginal pathways for biosynthesis, and that are needed by dividing progenitor cells. For some of the nutrients discussed, such as iodine and folate, the effects in humans are abundantly clear; for others, animal data are the most convincing. More human studies need to be conducted. We need a better understanding of diet and diet supplement intake during pregnancy and lactation and of whether diets are particularly low in some nutrients. Also, we need to understand how common genetic variations influence nutrient requirements during these periods. If we are going to supplement maternal and infant diets, first we must understand much more about the risks of having too much of a critical nutrient. Whatever the limitations of our current state of knowledge, it is apparent that pregnancy and lactation are periods during which good nutrition is exceptionally important. The infant is not protected from the inadequate diet of the mother.

Importance of methyl donors during reproduction

Evidence is growing that optimal dietary intake of folate and choline (both involved in one-carbon transfer or methylation) is important for successful completion of fetal development. Significant portions of the population are eating diets low in one or both of these nutrients. Folates are important for normal neural tube closure in early gestation, and the efficacy of diet fortification with folic acid in reducing the incidence of neural tube defects is a major success story for public health nutrition. Similarly, maternal dietary choline is important for normal neural tube closure in the fetus and, later in gestation, for neurogenesis in the fetal hippocampus, with effects on memory that persist in adult offspring; higher choline intake is associated with enhanced memory performance. Although both folates and choline have many potentially independent mechanisms whereby they could influence fetal development, these 2 nutrients also have a common mechanism for action: altered methylation and related epigenetic effects on gene expression.