Part III: Special Diets, Supplements, and Specific Nutrients During Pregnancy
Chapter 13 / Popular Diets 179
While managing a healthy weight throughout pregnancy may be a challenge for many women, it is important for women to embrace the fact that they are pregnant and need to gain weight in order to ensure having a healthy baby. Weight reduction during preg-nancy is discouraged and has been associated with neuropsychological abnormalities and low birth weight in the infant [2]. Conversely, excess weight gain can place women at higher risk for complications. Women should not use pregnancy as an excuse to eat excessively.
Although diet is a key component to weight maintenance, exercise, rest, and lifestyle are also highly important. During pregnancy, women should strive to eat a varied diet that encompasses all of the nutrients essential for fetal development.
This varied diet should be well balanced and not too high or low in any one of the macronutrients.
13.3 RECOMMENDATIONS FOR HEALTHY EATING
A complete approach to meeting nutrient and health needs during normal pregnancy is presented in Part 1 of this book. Specific aspects of this information in the context of weight management are presented here.
13.3.1 Energy
Activity level, age, height, and weight prior to pregnancy are all factors that are considered when determining an individual’s energy requirements. Although energy requirements vary from woman to woman, most women’s energy needs range from approximately 2,500 to 2,700 kcal daily [4]. Caloric requirements during the second and third trimesters of pregnancy are estimated to be 300 kcal/day (500 kcal/day for adolescents <14 years of age) above caloric requirements prior to pregnancy. The prepregnancy energy requirements used as a basis for this caloric estimation during pregnancy should account for age, activity level, and prepregnancy weight [4]. The Dietary Reference Intakes (DRIs) for pregnancy take into account increasing needs in support of fetal growth and appropriate maternal weight gain [5–7]. Butte and King [8] estimated energy costs of pregnancy using respiratory calorimetry throughout pregnancy and found that the daily cost of pregnancy increased by trimester. Weight gain during pregnancy should be individualized relative to prepregnancy BMI such that pregnancy outcome is improved, postpartum weight retention is minimized, and risk for adult chronic disease is reduced in the child [1]. In special situations such as adolescent pregnancy in which additional calories are necessary for the adolescent’s Table 13.2
ADA Position Paper: Guidelines for Weight Gain during Pregnancy
Body mass index (BMI) Recommended weight gain Weight gain/week after 12 weeks BMI <19.8 12.5–18 kg (28–40 lb) 0.5 kg (1 lb)
BMI 19.8–26 11.5–16 kg (25–35 lb) 0.4 kg (0.9 lb) BMI > 26–29 7–11.5 kg (15–25 lb) 0.3 kg (0.7 lb) BMI > 29 At least 7 kg (15 lb)
Twin pregnancy 15.9–20.4 kg (34–45 lb) 0.7 kg (1.5 lb) Triplet pregnancy Overall gain of 22.7 kg (50 lb)
own growth energy, requirements may be higher to maintain weight gain goals [2].
Pregnant adolescents less than 14 years of age require an additional 500 kcal/day [4, 9].
Likewise, women carrying twins need to consume 500 calories daily above energy needs for pregnancy as outlined above [7, 10]. Conversely, women who are over-weight or obese prior to pregnancy will require fewer calories due to the availability of stored energy. In any case, it is important that positive energy balance (energy in vs. energy out) exists such that a pregnant woman is in an anabolic state (energy in >
energy out). The degree of positive energy balance should be determined relative to an individual woman’s prepregnancy body weight (Tables 13.1, 13.2). Theoretically, an overweight woman may eat fewer calories when she becomes pregnant but still achieve an anabolic state because the degree of positive energy balance (calorie intake in excess of energy expended), while less than that prior to the pregnancy will gener-ally be sufficient to support fetal growth and development.
Once energy needs are established, it is important that the pregnant woman under-stands how to translate her calorie needs into appropriate food choices to support a healthy pregnancy. Requirements for some nutrients, such as protein, iron, and calcium, are increased during pregnancy. Therefore, pregnant women should focus on nutrient dense foods [foods that provide a lot of nutrients relative to the number of calories]. For example, one egg will contribute high-quality protein, essential fat, as well as a variety of vitamins and minerals, for approximately 75 calories. Too often patients are given calorie levels that may be specific to their needs without adequate instruction on how to incorporate these guidelines into their daily routines. Twenty-four-hour diet recalls con-ducted and evaluated by a registered dietitian, in combination with appropriate nutrition education materials, can be very useful in assisting the individual in translating their usual diet into meal plans that are consistent with recommendations for appropriate and healthy weight gain throughout pregnancy.
13.3.2 Diet Composition
The amount of energy contributed by the macronutrients—carbohydrate, protein, and fat—does not vary substantially during normal pregnancy. The role of each of these nutrients in normal physiology and metabolism remains intact with a heightened impor-tance for some functions in the context of fetal growth and development. For that reason, it is critical that pregnant women do not self-impose diet restrictions or extremes during pregnancy.
13.3.2.1 Carbohydrate
Carbohydrate is the brain’s main fuel and the nutrient that fuels muscles for daily tasks and exercise. The growing fetus relies on the mother’s carbohydrate supply.
A diet too low in carbohydrate can affect the energy level of the mother. During normal pregnancy, care should be taken to ensure that 50–60% of daily calories are provided as carbohydrate. Diets low in carbohydrate should not be attempted during pregnancy, as the effects of such a diet on fetal development are not known. Carbohydrate source should be well planned to ensure that the majority of carbohydrates are complex, with a limited consumption of refined sugar or simple carbohydrate. Examples of complex carbohydrates include bread, rice, beans, pasta, and potatoes. When grains are refined, they are stripped of many important nutrients, including fiber, which are important in
Chapter 13 / Popular Diets 181 pregnancy. Pregnant women should be advised to consume whole-grain bread, cereal, and pasta products. Fruits, vegetables, and whole-grain products are good sources of dietary fiber that are beneficial in preventing constipation during pregnancy. Foods with simple sugar like candy, soft drinks, and desserts should be limited during pregnancy as they are high in calories and low in nutritional value. These fat and sugar-laden foods can displace other more nutritious foods and contribute to accelerated weight gain. A woman requiring 2,500 kcal daily would need 275–330 g of carbohydrate daily. One slice of bread, 1/2 cup of cooked pasta, 1/2 cup dry cereal or a serving of fruit all provide
~15 g of carbohydrate per serving.
13.3.2.2 Protein
Adequate protein intake during pregnancy is important to maintain maternal health during pregnancy as well as provide important building blocks for fetal growth and development. Protein provides the structural framework for the body, is integral to the immune system, transports substances throughout the body, is the basis for many hor-mones and enzymes, and maintains fluid balance. Pregnant women need a minimum of 60 g of protein daily [2]. Good sources of dietary protein include meat, poultry, fish, dairy products, legumes, beans, and nuts. One ounce of meat, poultry, fish, or cheese provides 7 g of protein. One 8-oz. glass of skim milk provides 9 g of protein. Two 3-oz.
servings of meat, poultry, or fish and three 8-oz glasses of milk will provide the protein necessary to meet the protein needs of pregnancy.
13.3.2.3 Fat
Fat is more energy dense than carbohydrate or protein (9 kcal/g vs. 4 kcal/g for fat and carbohydrate and protein, respectively) when consumed within recommended guidelines, fat is beneficial to maternal health and fetal development. Fats are important in maintain-ing skin health, as a structural component of cells, for absorption of vitamins A, D, E, and K as regulatory messengers (hormones), hormone, and for immune function. Recent evidence suggests that omega-3 fatty acids consumed during pregnancy are beneficial to cognitive development in infancy and childhood [11–14]. Pregnant women should con-sume 25–30% of their daily energy as fatty acids. A woman requiring 2,500 kcal/day would need to consume 69–83 total grams of fats daily. These fat requirements should be met using vegetable-based oils made up of unsaturated fat rather than animal and plant-based saturated fats that can be more problematic to health [15].
Sources of unsaturated fats include olive oil, canola oil, peanut oil, sunflower oil, flax seed oil, and fish oil. Canola oil and flax seed oil are sources of the essential fatty acid α-linolenic acid. Dietary oils either derived or obtained directly from fish are particularly beneficial during pregnancy as fish contains a preformed source of docosahexaenoic acid (DHA) which is the metabolic end product of α-linolenic acid in the body [16] and pref-erentially transferred to fetal tissue during pregnancy [17–19]. Women should consume 300 mg of DHA daily during pregnancy [20]. Many pregnant women are concerned about eating fish during pregnancy due to potential contamination; however, women need to be educated about safe fish intake during pregnancy to ensure consumption of these impor-tant omega-3 fatty acids (http://www.cfsan.fda.gov/~comm/haccp4.html). Omega-6 fatty (linoleic) acid should make up 2% of total energy during pregnancy. This recommendation does not differ from the recommendation for the general adult population [20].
Sources of saturated fat include whole milk, beef, cheese, lard, shortening, and palm and coconut oil. No more than 10% of daily calories should come from a saturated fat source. A woman who requires 2,200 kcal daily should consume no more than 24 g of saturated fat daily.
13.3.3 Micronutrients
Pregnancy is a time to ensure adequate micronutrient intake in addition to sufficient energy and macronutrients for optimal fetal development. The key to ensuring dietary adequacy of the micronutrients is a varied diet that includes multiple foods from all food groups. Factors that place pregnant women at risk for micronutrient deficiencies include diets that restrict energy, diets that omit one or more major food groups, food insecurity, food intolerances, allergy or food aversions. Dietary plans should be devel-oped according to risk factors that include alternative dietary sources. Attention should also be given to potential micronutrient deficiencies associated with the respective types of diets. Several micronutrients are of critical importance to the fetus’s growth and development (Table 13.3).
13.4 ACCEPTABLE PHYSICAL ACTIVITY AND EXERCISE PLANS A plan for regular exercise is another key component of weight management [21–25].
Women need to dispel the myth that women should “take it easy” during pregnancy.
Chapter 3, “Physical Activity and Exercise in Pregnancy,” provides a thorough dis-cussion regarding physical activity and exercise during pregnancy. In brief, pregnant women should consult their doctor before initiating an exercise program or modifying their existing regimen to rule out complications [24]. Light-to-moderate physical activity does not negatively influence fetal development for a normal, uncomplicated pregnancy [21, 25]. A properly designed exercise program during pregnancy is beneficial and can contribute to healthy weight management at this time [22, 24].
In addition to adequate calorie and nutrient intake, and appropriate exercise and physical activity, various lifestyle factors should be considered when planning for appropriate weight gain during pregnancy. Occupation, leisure activities, stress level, and habitual dietary behaviors (i.e., eating out, eating cues, binge eating) are important considerations for weight management programs. Behavior modification strategies may need to be implemented for women who have problems with habitual unhealthy dietary behaviors (See Chap. 9, “Anorexia Nervosa and Bulimia Nervosa during Pregnancy”). All of these factors should be taken into consideration in consultation with a registered dietitian and in collaboration with the supervising physician.
Table 13.3
Micronutrient Defi ciency Risks Associated with Various Popular Diets Popular diet type: Micronutrient
Fat restrictive Fat soluble vitamins (A, D, E, K), essential fatty acids Protein restrictive Iron, vitamin B12, zinc, magnesium, essential amino acids
Non-dairy Calcium, vitamin D
Carbohydrate restrictive B vitamins, vitamins C, A, K and D, potassium, fiber