and fetal tissues, most of which is accumulated during the last half of pregnancy [27]. The efficiency of absorption of zinc during pregnancy does not appear to change sufficiently to meet zinc needs in the absence of an increased dietary intake [28]. The increased recommendation for zinc of 3 mg/day in pregnancy is based on the accumulation of fetal and maternal zinc of 0.73 mg/day during the last quarter of pregnancy, accounting for a 27% efficiency of absorption [20].
1.2.4 Nutrients without Increased Requirements during Pregnancy
The fact that requirements for some nutrients do not increase during pregnancy does not imply that these nutrients are not critical to maternal and fetal health. Calcium is a case in point. The needs of the fetus for calcium are substantial, averaging 300 mg/
day. However, due to homeostatic adjustments, the dietary requirements for calcium do not change during pregnancy. An integrated system of hormones, namely parathyroid hormone and 1,25-dihydroxyvitamin D, regulate intestinal absorption, urinary excre-tion, and bone flux of calcium. During pregnancy, the efficiency of calcium absorption increases by nearly 50%, such that fetal needs appear to be met without increasing cal-cium intake or net losses of maternal bone mineral [11, 29].
Even though the DRI for calcium does not increase during pregnancy, it should be noted that many women fail to meet calcium requirements. According to data from the 1999–2000 NHANES, the average calcium intake of women of childbearing age is 797 mg/day, far below recommended levels [16]. Phosphorus absorption is also increased in pregnancy by changes in calcitropic hormone concentrations. Therefore, as with calcium, the DRI in pregnancy for phosphorus remains the same as for nonpregnant women [30].
For some of the other nutrients, the available evidence is generally not sufficient to warrant recommending an increased intake during pregnancy (e.g., biotin, vitamin K, vitamin E, chloride, fluoride). For yet other nutrients, the intake of nonpregnant women already appears ample to meet the small increased demands during gestation (e.g., sodium, potassium, vitamin D) [15, 20, 30–32].
1.3 DIETARY GUIDELINES
The Dietary Guidelines for Americans translates scientific information on nutrient requirements and dietary characteristics that promote good health into recommendations and advice for the food intake by the general public. Thus, the Dietary Guidelines is the backbone of nutrition education efforts throughout the country. They also reflect nutri-tion policy in the United States because it provides the basis for the all federal food and nutrition programs, i.e., food stamps; Women, Infants, and Children (WIC); school meal programs; and emergency feeding efforts.
The first edition of the Dietary Guidelines was released in 1980, and then it has been revised every 5 years. The sixth, and latest, edition was released in 2005 [33]. The first five editions of the Guidelines consisted of 7 or 10 statements providing guidance on how to adopt a pattern of eating that supports good health. The statements were remark-ably consistent from one edition to the next [34]. Common themes in all five editions included eating a variety of foods, maintaining body weight, and limiting dietary fat, sugar, sodium, and alcohol intakes. A recommendation to eat foods with adequate starch
and fiber in the first two editions evolved into recommendations to choose a diet with plenty of fruits, vegetables, and grains in 1990 and thereafter.
A very different approach was taken by the 2005 Dietary Guidelines Advisory Com-mittee [35]. Specifically, the ComCom-mittee was charged with conducting an evidence-based review of the scientific literature on diet and health rather than writing a more general document. To address that charge, the Committee initially posed over 40 specific ques-tions related to dietary guidance, thoroughly reviewed the scientific literature pertaining to those questions, and deliberated on the results. Some of the questions were dropped because of incomplete or inconclusive data. Consequently, the Committee wrote con-clusive statements and a comprehensive rationale supporting those statements for 34 of the original questions. After some minor revisions and modifications, the 2005 Dietary Guidelines for Americans was drafted from the conclusions put forth by the Advisory Committee. The 2005 Dietary Guidelines included 23 key recommendations and 18 rec-ommendations for specific population groups, for a total of 41 recrec-ommendations [33].
These 41 recommendations are intended to be the primary source of dietary informa-tion for policymakers, nutriinforma-tion educators, and health providers in the United States.
However, it is impossible for the public to assimilate and apply so many different recom-mendations to their own food choices. Therefore, additional documents were developed specifically for the public. One is a bulletin entitled, “Finding your way to a healthier you,” written jointly by the Departments of Agriculture and Health and Human Services.
The bulletin synthesizes the 41 recommendations from the “policy document” into three primary messages:
● Make smart choices from every food group.
● Find your balance between food and physical activity.
● Get the most nutrition out of your calories.
The bulletin emphasizes the kinds of foods, appropriate amounts, and how often to eat certain foods or food groups. A basic underlying premise of the Dietary Guidelines is that nutrient requirements should be met primarily from foods, and that this is best accomplished by choosing a diverse, nutrient-dense diet within one’s dietary energy needs. Support for this premise is provided by the research of Foote and colleagues who found that the diets of American adults who met the current DRIs selected a variety of foods daily from each of the five food groups (grains, fruits, vegetables, dairy, and meat/protein) [36].
1.4 DEVELOPMENT OF A FOOD PATTERN MEETING NUTRIENT RECOMMENDATIONS
The key recommendations in the 2005 Dietary Guidelines regarding nutrient ade-quacy emphasize the importance of consuming a variety of nutrient-dense foods and beverages within and among the five basic food groups. The 2005 Dietary Guidelines Advisory Committee recognized, however, that the general public would benefit from guidance on specific food patterns that meet the DRIs. The Dietary Guidelines’ key recommendations emphasize the types of foods to select, but lack the specificity needed by an individual to make selections that meet his/her requirements within dietary energy needs. Thus, the Advisory Committee collaborated with staff from the US Department
Chapter 1 / Nutrient Recommendations and Dietary Guidelines for Pregnant Women 17 of Agriculture’s (USDA’s) Center for Nutrition Policy and Promotion (CNPP) on their update of the food pattern from the original Food Guide Pyramid to meet the nutrient recommendations from the Institute of Medicine Dietary Reference Intake reports [30, 37–41]. This new food pattern is the basis for the revised USDA Food Guidance System, MyPyramid [42].
The method for developing the food pattern, based on the model used to develop the Food Guide Pyramid, involves a five-step process.
1. Establish energy levels. Appropriate energy levels for various population groups based on age, gender, and activity level were established using IOM’s EER equations [4].
Based on these results, modifi cations of the food pattern were developed for caloric levels from 1,000 to 3,200 kcal/day in 200-calorie increments.
2. Establish nutrition goals for the food pattern. Nutrient goals were the RDAs for vita-mins, minerals, electrolytes, and macronutrients published by the IOM between 1997 and 2004 [4–9].
3. Assign nutrient goals to each specifi c energy level. The nutrition goals assigned to each energy level were the goals for age/gender groups that most closely matched the specifi c energy level. For example, the 1,800 kcal/day level included the goals of females aged 31–50 years, males/females aged 9–13 years, and females aged 14–18 years.
4. Assign nutrient values for each food group and subgroup. The nutrient values assigned to each food group (i.e., fruits, milk, meat and beans, whole grains, enriched grains, dark green vegetables, orange vegetables, legumes, starchy vegetables, and other vegetables) were weighted averages of the nutritional value of foods consumed by Americans within that group based on results of the nationwide food consumption surveys (i.e., the National Health and Nutrition Examination Survey 1999–2000). For example, broccoli makes up 44% of the dark green vegetables consumed, spinach is 21%, and the remaining 35% is composed of other dark green vegetables [43]. Therefore, the nutritional values assigned to dark green vegetables were based on 0.44 for broccoli, 0.21 for spinach, and 0.35 for others. Nutrient values for each group were a weighted average of nutrient-dense forms—low-fat and no-added-sugar forms—of the various foods in each group. An exception is that fat-free milk was the single food item used for the milk group.
5. Determine the daily intake amounts for each food group or subgroup. Starting from the original Pyramid food pattern at three calorie levels, the amounts of each food group or subgroup were increased or decreased in an iterative manner until the pattern for each of the twelve energy levels met its nutrition goals or came within a reasonable range.
There are advantages and disadvantages to this approach for developing food patterns that meet the RDAs for all Americans. The fact that it builds on the model used for the previous Pyramid provides continuity in food guidance over time. Also, it integrates the entire gamut of IOM recommendations into a lone food intake pattern. Limitations include basing the nutrient profile for each food group on the food consumption pat-terns of Americans within that group. Americans may not choose foods rich in certain nutrients within that group. For example, Americans eat very few nuts relative to other choices in the meat, poultry, fish, dry beans, eggs, and nuts group. Consequently, the vitamin E content of that food group tends to be low. Thus, the intake pattern, like typi-cal American diets, is low in vitamin E, and it is difficult for most individuals to meet the vitamin E DRI. In the future, separation of this diverse food group into animal and plant
sources may improve the capacity to meet the DRI for vitamin E as well as for other nutrients, such as potassium. However, the complexity of the food pattern increases with each subgroup added to the pattern. For example, vegetables were broken down into
“dark green,” “orange,” “legumes,” “starchy,” and “other”; grains were subdivided into
“whole” and “enriched.” This was done in recognition of their different nutrient contents and to encourage increased consumption of some subgroups to meet the AIs for several nutrients. Finally, only the lowest fat forms of milk products (i.e., fat-free milk) and lean meats are used in the patterns. If higher fat forms are consumed, that energy needs to be considered to assure that the total intake of energy and saturated fat does not exceed the recommendations. It is important to remember that foods with added sugar will also contribute to the total energy intake.
1.5 RECOMMENDED FOOD PATTERNS FOR PREGNANCY
Specific food patterns are available for pregnant women at the MyPyramid.gov website.
The woman is asked to specify her age, due date, height, weight, and physical activity level. She will then receive a menu plan for the first, second, and third trimesters. The amounts of food increase slightly with advancing pregnancy to meet increased energy and nutrient needs in late gestation. We compared the nutrients provided in each of the food intake patterns between 2,000 and 3,000 kcal/d for non-pregnant women to the rec-ommended nutrient intakes for pregnancy and found that the amount of macronutrients, vitamins, and minerals in the patterns for non-pregnant women meet pregnancy standards except for three nutrients—iron, vitamin E, and, to a lesser extent, potassium (Table 1.4).
Thus, one could continue to base dietary guidance for pregnant women on the MyPyramid food patterns recommended for non-pregnant women. As mentioned above, the iron DRI during pregnancy, 27 mg/day, is higher than the amount that can be met from foods. At the first prenatal visit, all women are advised, therefore, to take a 30 mg iron supplement daily [44]. The food patterns only provide about 60–80% of the pregnancy vitamin E recom-mendation. The patterns are also insufficient in vitamin E for nonpregnant adults, provid-ing only 50–70% of the requirement. The Dietary Guidelines Advisory Committee found that it was very difficult to develop food patterns meeting the vitamin E RDAs that also remained within the guidelines for dietary fat since vegetable oils are a primary source of vitamin E. Nuts are also a good source of vitamin E, and the Committee considered mak-ing nuts a subgroup of the meat group in order to emphasize their importance in the diet.
But, since evidence of health problems among Americans due to insufficient intakes of vitamin E was lacking, the Committee decided to allow the vitamin E intakes to fall short of the RDAs. The vitamin E DRI can be met, however, by selecting vitamin E fortified ready-to-eat cereals, almonds, sunflower seeds, avocados, and certain oils (i.e., sunflower and cottonseed). Potassium intakes in the 2,000-, 2,200-, and 2,400-kcal patterns range from 85 to 95%, the pregnancy DRI. This potassium intake is likely within an acceptable range, but the amount in the diet can be enhanced by increasing milk, white potato, tomato, or orange juice intakes.
The amounts of protein, carbohydrate, fat, and types of fat in the six food patterns are shown in Table 1.5. The percent of energy as protein is about 18%, as carbohydrate about 55%, and as fat about 27%. Saturated fat makes up about 7.4% of the energy, monounsaturated fat about 10%, and polyunsaturated fat about 8%. The recommended