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11 Introduction In addition to increased energy requirements during pregnancy, a topic covered in Part I of this volume, it has long been recognized that pregnancy also increases a woman's need for protein, vitamins, and minerals. Some re- ports suggest that the usual dietary intake of certain nutrients is inadequate to meet the needs of pregnant women, and many suggest that supplemental intake of one or more nutrients might be desirable. Recently, health care providers have asked for guidance in counseling pregnant women about the use of nutrient supplements with regard to their safety, efficacy, and appropriate dosage if used. In the past, several reports issued by expert Food and Nutrition Board (FNB) committees on maternal nutrition have given detailed consideration to certain vitamins, minerals, and protein. One of these reports contained an overview of laboratory indices of a broad spectrum of nutrients (NRC, 1978~; another covered certain practices, such as pica (the ingestion of nonfood substances such as laundry starch) and vegetarianism, that may influence nutritional status during pregnancy (NRC, 1982~. Four reports recommended 30 to 60 mg of supplemental iron per day (NRC, 1970, 1980, 1981, 1982), and two recommended supplemental folic acid (NRC, 1970, 1980) during pregnancy as a means of reducing the risk of anemia. No FNB reports have recommended the routine use of multivitamin-mineral supplements. 237
238 DIETARY INTAKE AND NUTRIENT SUPPLEMENTS PREVIOUS RECOMMENDATIONS FROM PROFESSIONAL ORGANIZATIONS Professional organizations concerned with maternal and child health have made recommendations pertaining to nutrient intake and supplement use during pregnancy. For example, a special task force of the American Dietetic Association released the following statement regarding vitamin and mineral supplementation. Although this statement was targeted toward the general population, it specifically mentions pregnant women: Healthy children and adults should obtain adequate nutrient intakes from dietary sources. Meeting nutrient needs by choosing a vanes of foods in moderation, rather than by supplementation, reduces the potential risk for both nutrient deficiencies and nutrient excesses. Individual recommendations regarding supplements and diets should come from physicians and registered dietitians. Supplement usage may be indicated in some circumstances including: Women who are pregnant or breastteeding need more of certain nutnents, especially iron, folio add and calcium (ADA, 1987, p. 1342~. A virtually identical statement was released by the American Institute of Nutrition jointly with the American Society for Clinical Nutrition (Callaway et al., 1987~. In its publication Standards for Obstetric-Gynecologic Services, the American College of Obstetricians and Gynecologists (ACOG) included the following statement: Protein, iron, folio acid, and certain other vitamins and minerals are required in greater amounts during pregnancy. If these needs are not met by increased dietary intake, a vitamin/mineral supplement equal to the recommended dietary allowances (RDA) for pregnant women should be given (ACOG, 1985, p. 20~. In a separate publication the same year, the Disk Force on Adolescent Pregnancy (1985) addressed nutritional needs of pregnant adolescents in somewhat more detail, providing specific suggestions to consume protein- rich foods with a goal of achieving a daily protein intake of 76 to 78 g. Regarding iron, it stated: "Pregnancy requires 30-60 mg of iron per day. Since dietary sources of iron are limited, and diet alone cannot supply the needed iron, a supplement is recommended in appropriate amounts to meet the increased need" Desk Force on Adolescent Pregnancy, 1985, p. 28~. It also recommended a calcium intake of 1.2 to 1.6 g daily and stated: "If the teen's normal diet includes large amounts of mink and daily products, supplemental calcium will be unnecessary" Desk Force on Adolescent Pregnancy, 1985, p. 29~. Further relevant recommendations include the following: "During all pregnancies, a supplement of folio acid not to exceed 1 mg per day is recommended" (p. 29) and "Because certain vitamins may cause fetal malformations, general recommendations for a vitamin supplement would be unwise" (p. 29~.
INTRODUCT ON 239 The American Academy of Pediatrics (AAP) and ACOG jointly pub- lished Guidelines for Perinatal Care (AAP/ACOG, 1988), which includes slightly different recommendations: folio acid supplementation of at least 400 Friday and, for adolescents, calcium and phosphorus supplementation or additional milk (more than 1 quart daily). With regard to other vitamins and minerals: The increased amounts of other vitamins and minerals recommended during pregnancy . . . can usually be obtained through dietary intake, and the routine use of a multivitamin supplement is not necessary. If there are doubts about the adequacy of a patient's diet, however, a vitamin and mineral supplement that provides the recommended dietary allowances can be given safely. It is important to avoid excessive vitamin and mineral intakes (de, more than twice the recommended dietary allowances) during pregnancy because both fat-soluble and water-soluble vitamins may have toxic effects (AAP/ACOG, 1988, p. 196~. The recommendations made by these professional groups were strongly influenced by earlier FNB reports, including the 1980 (ninth) edition of Recommended Dietary Allowances (NRC, 1980~. The recently published tenth edition of the RDAs (NRC, 1989) includes a number of revised recommendations for nutrient intake. For example, the 1989 RDA for folate (often called folacin or folio acid) intake during pregnancy is 400 ,ug, compared with 800 fig in 1980. The 1989 RDAs for pregnant women appear in Table 11-1. Directions on the labels of certain prenatal vitamin-mineral supple- ments may lead to intakes well in excess of the 1989 RDAs. This is not readily apparent to either the user or the physician issuing the prescrip- tion, since label information is expressed in terms of the Food and Drug Administration's U.S. Recommended Daily Allowances (U.S. RDA) not the RDAs, which are substantially different for several nutrients (see Able 11-1~: 100% of the U.S. RDA may be more or less than the RDN The safety of vitamin-mineral supplementation deserves close examination, as does the possibility of benefit to mother or infant. USAGE PATTERNS Prenatal vitamin-mineral supplementation has been widespread in the United States for many years. Approximately 92% of 7,825 married mothers* in the 1980 National Natality Survey reported taking vitamin supplements during pregnancy (K Keppel, National Center for Health Statistics, personal communication, 1988), as did nearly 88% of the 116 * Unmarried women were not interviewed in the 1980 National Natality Survey. For more infor- mation about the survey, see Chapter 5.
240 DIETARY INTAKE AND NUTRIENT SUPP~FM:ENTS TABLE 11-l Recommended Dietary Allowances (RDAs) and Estimated Safe and Adequate Daily Dietary Intakes (ESADDIs) Compared with U.S. Recommended Daily Allowances (U.S. RDAs) for Nonpregnant and Pregnant Women U.S. RDAb RDA or ESADDI for Adults and Pregnant or Pregnant Adult Children over Lactatin' Nutrient Womena 3 Years OldC Women RDA: Protein60 g65 g65 g Vitamin A800 mg REe5,000 IU8,000 IU Vitamin D10 ,ugf400 IU400 IU Vitamin E10 mg of a-TEg30 IU30 IU Vitamin K65 ,ugh Vitamin C70 mg60 mg60 mg Thiamin1.5 mg1.5 mg1.7 mg Riboflavin1.6 mg1.7 mg2.0 mg Niacin17 mg NE'20 mg20 mg Vitamin B62.2 mg2.0 mg2.5 mg Folacin400 ,ug400 ,ug800 ~g Vitamin B~22.2 ,ug6 ,ug8 ,ug Calcium1,200 mg1,000 mg1,300 mg Phosphorus1,200 mg1,000 mg1,300 mg Magnesium3()0 mg400 mg450 mg Iron30 mg18 mg18 mg Zinc15 mg15 mg15 mg Iodine175 ,ug150 ,ug150 ,ug Selenium65,ug ESADDI: Biotin30-100 ,ug300 ,ug300 ,ug Pantothenic acid4-7 mg10 mg10 mg Copper1.5-3.0 mg2 mg2 mg Manganese2.0-5.0 mg Fluoride1.5-4.0 mg Chromium50-200 ,ug Molybdenum75-250,ug a From NRC, 1989. b From National Nutrition Consortium, 1975. c Used in the labeling of most foods, e.g., ready-to-eat cereals, and vitamin and mineral supplements for adults. Used in the labeling of vitamin-mineral supplements designed for pregnant and lactating women. t 1 RE (retinol equivalent) = 1 ,ug of retinol, ~ ,ug ot ,~-carotene, or l~ ,ug OI Olner provitamin A carotenoids; whereas 1 IU is usually equated to 0.3 ,ug of retinol and to 0.6 ,ug of ,B-carotene. By calculation, 8,000 IU of vitamin A from vitamin supplements or cereal fortified with retinol equals 2,400 RE. f 1 ,ug of vitamin D (cholecalciferol) = 40 IU. g 1 a-TE (tocopherol equivalent) = 1 mg of RRR-a-tocopherol = 1.49 IU RRR-a tocopherol = 0.74 IU of all-rac-a-tocopherol (the synthetic form). h = Not established. i 1 NE (niacin equivalent) is equal to 1 mg of niacin or 60 mg of dietary tryptophan.
INTRODUCTION 241 pregnant women in the U.S. Department of Agriculture's (USDAs) Con- tinuing Survey of Food Intake by Individuals (S. Krebs-Smith, Food and Nutrition Service, personal communication, 1988~. Vitamin-mineral supplementation early in pregnancy, before prenatal care, may be of particular interest because of associations (both positive and negative) between supplement use and teratogenesis. Although supplement usage rates by women in the first few weeks of gestation have not been reported, they may parallel those reported for nonpregnant, nonlactating women in the childbearing years, which vary substantially by ethnic back- ground, education, and income (Block et al., 1988; Koplan et al., 1986~. The less advantaged groups have lower supplement usage rates. For exam- ple, 55% of all women in their childbearing years reported taking a vitamin or mineral supplement regularly or occasionally (USDA, 1987b) compared with 48% of low-income women who were not participating in the Food Stamp Program and 39% of those who were (USDA, 1987a). Analysis of data collected in the first (1971-1975) National Health and Nutrition Examination Survey indicates that among females between 25 and 34 years of age, 26.4% of the whites and 15.5% of the blacks reported regular use of vitamin and mineral supplements (Block et al., 1988~. SCOPE OF REPORT The Subcommittee on Dietary Intake and Nutnent Supplements Dur- ing Pregnancy was asked to review recent studies of dietary intake, sup- plement usage, laboratory indices reflecting nutrient intake, and nutrient requirements as a basis for developing conclusions and recommendations pertaining to the use of nutrient supplements during pregnancy. The spon- sor, the Bureau of Maternal and Child Health and Resources Development of the U.S. Department of Health and Human Services, also asked the subcommittee to give special attention to calcium, iron, zinc, folate, and protein most of which have been the subject of an increasing amount of research because of their suspected influence on the short- and long-term health status of mothers or their infants. The subcommittee considered the following questions as they pertain to pregnancy: · For which nutrients is it reasonable to expect that food alone will provide adequate intake? · For which nutrients, if any, is supplementary intake from pharma- ceutical preparations desirable? · If supplementation is recommended or practiced, what level is appropriate? · Is there danger of toxicity from use of any nutrient supplements?
242 DIETARY INTAKE AND NUTRIENT SUPPLEMENTS Do interactions among nutrients and between drugs and nutrients substantially change the pregnant woman's ability to achieve satisfactory nutritional status? · Should recommendations differ for adolescents, for women aged 35 and over, and for women of different ethnic backgrounds? These are questions faced by pregnant women as well as by the practitioners and the health and nutrition programs that serve them. New findings relative to nutrient-nutrient interactions may be relevant in providing nutritional advice to pregnant women, both from the stand- point of desirable types of food combinations and when considering the use of supplemental nutrients. In addition, the subcommittee considered the use of such substances as street drugs, alcohol, and tobacco, which may have far-reaching consequences on the developing fetus and the fam- ily unit. It recognized the need to determine the nutritional implications of different forms of substance abuse and to develop realistic approaches to modifying food intake, recommending supplement use, or delivering nutrition services without losing sight of the importance of taking steps to modify the harmful practice. The subcommittee also searched for ev- idence relating differences in body size, genetic makeup, age, recent life circumstances (e.g., living in a refugee settlement), and customary eating practices to the need for supplementation. However, the lack of scientific data limited the extent to which the subcommittee was able to address these issues. UNDERLYING ASSUMPTIONS During the course of its deliberations, the subcommittee agreed that the following concepts were important in guiding its work: · Supplementation is justified only when there is evidence that dietary intake of the nutrient is likely to be sufficiently low to produce adverse effects on maternal or fetal health or on pregnancy outcomes. · Laboratory indices of nutrient deficiencies developed for nonpreg- nant women are frequently inappropriate for women who are pregnant. Standards for pregnant women are often unavailable. This is an additional reason why optimal maternal and fetal health should be a major criterion on which to judge the need for supplementation. · Supplementation is an intervention, for which both safety and efficacy are of concern. It is important to review the effects of nutrient supplements during organogenesis, which occurs very early in pregnancy. · The practical issue of the patient's willingness to take supplements must be considered when making recommendations for supplementation.
INTRODUCTION 243 ORGANIZATION OF THE REPORT Chapter 12 presents useful background information pertaining to the assessment of prenatal nutrient needs. Chapter 13 presents an analysis of evidence about the dietary intake of pregnant women. These two chap- ters provide a framework for the next six chapters (Chapters 14 through 19), which address specific nutrients of possible concern during pregnancy. In Chapter 20, the subcommittee presents data on interactions among food, nutrients, and certain nonnutritive substances (e.g., cigarettes, coffee or caffeine, alcohol, marijuana, and cocaine) used during pregnancy and examines how these interactions may influence recommendations for sup- plementation. Periconceptional nutrition and the evidence for and against the use of multivitamins in the prevention of neural tube defects are d~s- cussed In Chapter 21. Chapter 1 contains the subcommittee's conclusions and recommendations. REFERENCES AAP/ACOG (American Academy of Pediatrics/American College of Obstetricians and Gynecologists). 1988. Guidelines for Perinatal Care, 2nd ed. American Academy of Pediatrics, Elk Grove, Ill. 356 pp. ACOG (American College of Obstetricians and Gynecologists). 1985. Standards for Obstetric-Gynecologic Services, 6th ed. The American College of Obstetricians and Gynecologists, Washington, D.C. 109 pp. ADA (American Dietetic Association). 1987. Recommendations concerning supplement usage: ADA statement. J. Am. Diet. Assoc. 87:1342-1343. Block, G., C. Cox, J. Madans, G.B. Schreiber, L. Licitra, and N. Melia. 1988. Vitamin supplement use, lay demographic characteristics. Am. J. Epidemiol. 127:297-309. Callaway, C.W., KW. McNutt, R.S. Rivlin, A.C. Ross, H.H. Sanstead, and A.P. Simopoulos. 1987. Statement on vitamin and mineral supplements. J. Nutr. 117:1649. Koplan, J.P., J.L. Annest, P.M. Layde, and G.L Rubin. 1986. Nutrient intake and supplementation in the United States (NHANES II). Am. J. Public Health 76:287-289. National Nutrition Consortium. 1975. Nutrition Labeling: How it Can Work for You. National Nutrition Consortium, Bethesda, Md. 134 pp. NRC (National Research Council). 1970. Maternal Nutrition and the Course of Pregnancy. Report of the Committee on Maternal Nutrition, Food and Nutrition Board. National Academy of Sciences, Washington, D.C. 241 pp. NRC (National Research Council). 1978. Laboratory Indices of Nutritional Status in Pregnancy. Report of the Committee on Nutrition of the Mother and Preschool Child, Food and Nutrition Board. National Academy of Sciences, Washington, D.C. 195 pp. NRC (National Research Council). 1980. Recommended Dietary Allowances, 9th ed. Report of the Committee on Dietary Allowances, Food and Nutrition Board, Division of Biological Sciences, Assembly of Life Sciences. National Academy Press, Washington, D.C. 185 pp. NRC (National Research Council). 1981. Nutrition Services in Perinatal Care. Report of the Committee on Nutrition of the Mother and Preschool Child, Food and Nutrition Board, Assembly of Life Sciences. National Academy Press, Washington, D.C. 72 pp. NRC (National Research Council). 1982. Alternative Dietary Practices and Nutritional Abuses in Pregnancy: Proceedings of a Workshop. Report of the Committee on Nutrition of the Mother and Preschool Child, Food and Nutrition Board, Commission on Life Sciences. National Academy Press, Washington, D.C. 211 pp.
244 D ETARY INTAKE AND NUTRIENT SUPPLEMENTS NRC (National Research Council). 1989. Recommended Dietary Allowances, 10th ed. Report of the Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences. National Academy Press, Washington, D.C. 284 PP Ask Force on Adolescent Pregnancy. 1985. Adolescent Perinatal Health: A Guidebook for Services. The American College of Obstetricians and Gynecologists, Washington, D.C. 40 pp. USDA (U.S. Department of Agriculture). 1987a. Nationwide Food Consumption Survey. Continuing Survey of Food Intakes By Individuals. Low-Income Women 19-50 Years and Their Children 1-5 Years, 1 Day, 1986. Report No. 86-2. Nutrition Monitoring Division, Human Nutrition Information Service, U.S. Department of Agriculture, Hyattsville, Md. 166 pp. USDA (U.S. Department of Agriculture). 1987b. Nationwide Food Consumption Survey. Continuing Survey of Food Intakes by Individuals. Women 19-50 Years and Their Children 1-5 Yeam, 1 Day, 1986. Report No. 86-1. Nutrition Monitoring Division, Human Nutrition Information Service, U.S. Department of Agriculture, Hyattsville, Md. 98 pp.