Energy and Macronutrients

Energy needs increase in the last two trimesters to support the maternal and fetal products of pregnancy as well as spare protein to build these new tissues. Weight gain serves as a proxy indicator that these tissues have developed normally (see Chap. 2, "Optimal Weight Gain"). What is unique in AN is the controlled intake of food energy in those with restricting type. Intakes of 200-700 kcal per day, typical of an individual with restricting-type AN, are simply inadequate to supply the energy required for most successful pregnancies. In binge eating-purging-type AN and purging-type BN, adequate and even overly abundant kilocalories may be consumed—but are purged before the body has the opportunity to either fully digest or absorb nutrients. With nonpurging-type BN, adequate energy may be consumed; however, laxative, diuretic, and/or enema use as well as excessive exercise may result in malabsorption, excessive excretion, or altered utilization of nutrients such that the stream of nutrients is inadequate during pregnancy.

To provide an adequate amount of glucose and nonprotein kilocalories, over 175 g of carbohydrate per day are needed in pregnancy. If composed solely of carbohydrate, 700 kcal would meet this minimum need; however, most intakes of women with active restricting type AN do not contain adequate carbohydrate levels. Conversely, foods

Nutrients of Special Concern in Women with Anorexia Nervosa (AN) or Bulimia Nervosa (BN) During Pregnancy

Nutrient

Concern in AN or BN

Dietary Reference Intakea during Pregnancy

Role during Pregnancy

Energy and macronutrients

Energy

Carbohydrate

Protein

Fat (lipids)

Vitamins

  • Folate
  • Pyridoxine (B6)
  • Cobalamin (B12)
  • Vitamin A

Minerals

Energy severely restricted in AN

(200-700 kcal per day) or excessive (1,500-

9,000 kcal per binge episode, followed by compensatory behavior) with limited energy availability

Severely restricted in AN or binged but purged in BN

Adequate proportion relative to energy intake, but total intake limited in AN

Intake generally avoided or purposefully restricted

Poor intake and subclinical deficiency Poor intake and subclinical deficiency Poor intake (especially in vegans) and subclinical deficiency Hypercarotenemia in AN due to catabolism

In AN, skeletal calcium stores may be compromised

Poor intake (especially in vegans)

+340kcal per day in second trimester and +452kcal per day in third trimester

Minimum of 175 g per day 71 g per day

13 g per day of linoleic acid and 1.4 g per day of alpha-linolenic acid

600 meg per day 1.9 mg per day 2.6 meg per day

770 meg retinal activity equivalents per day

1,000 mg per day 27 mg per day

Energy to supply production and growth of maternal and fetal tissues of pregnancy

Glucose availability and non-protein energy needs for mother and fetus Amino acid supply for maternal and fetal tissue production, maternal blood volume expansion and fluid balance

Growth, development, and function of fetal nerve and brain tissue, cell membranes, and organs

Fetal neural tube formation Coenzyme for maternal energy metabolism Required for maternal folate metabolism and DNA and RNA synthesis for fetal tissues Cellular differentiation for fetal tissue development

Fetal skeletal mineralization

Hemoglobin synthesis; support of maternal blood volume expansion

(continued)

Table 9.2

Nutrients of Special Concern in Women with Anorexia Nervosa (AN)

or Bulimia Nervosa (BN) During Pregnancy

Nutrient

Concern in AN or BN

Dietary Reference Intakea during Pregnancy

Role during Pregnancy

• Zinc

  • Potassium
  • Sodium
  • Chloride
  • Poor intake (especially in vegans)
  • Hypokalemia due to purging and other compensatory behaviors
  • Hyponatremia due to purging and other compensatory behaviors
  • Hypochloremia due to purging and other compensatory behaviors
  • 11 mg per day
  • 4.7 g per day
  • 1.5 g per day
  • 2.3 g per day
  • DNA and RNA synthesis and cofactor for enzymes
  • Transmission of nerve impulses; major intracellular cation
  • Transmission of nerve impulses; major extracellular cation
  • Part of hydrochloric acid in stomach; transmission of nerve impulses; major extracellular anion

Compiled from Food and Nutrition Board, Institute of Medicine (1988) Dietary Reference Intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. National Academies Press, Washington, D.C.; Food and Nutrition Board, Institute of Medicine (2001) Dietary Reference Intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. National Academies Press, Washington, D.C.; Food and Nutrition Board, Institute of Medicine (1997) Dietary Reference Intakes for calcium, phosphorus, magnesium, vitamin D, and fluoride. National Academies Press, Washington, D.C.; and Food and Nutrition Board, Institute of Medicine (2004) Dietary Reference Intakes for water, potassium, sodium, chloride, and sulfate. National Academies Press, Washington, D.C. aFrom [28]

ingested during binge eating episodes have been shown to contain high amounts of carbohydrate [21, 22]. Yet, if purged, malabsorbed, or used to support increased energy expenditure of exercise, this carbohydrate is not readily available to support growth and development of the mother and fetus. Low-carbohydrate diets do not meet the minimum need for carbohydrate during pregnancy (see Chap. 13, "Popular Diets"). Moreover, these diets result in mild ketosis [23], which may pose harm to the fetus [24].

Protein intake is crucial to supply the amino acids needed for production of new tissues and to support blood volume expansion and fluid balance. Restricted intake and purging and nonpurging behaviors do not allow for the provision of adequate protein during pregnancy. Vegetarianism is common in women with eating disorders [25]. Dietary protein and specific amino acid deficiencies may be of concern in women with AN or BN who are also vegetarians (see Chap. 14, "Vegetarian Diets in Pregnancy).

A small portion of total kilocalories as dietary fat is needed to supply the essential fatty acids—linoleic acid and alpha-linolenic acid. These fatty acids are crucial, however, to the growth, development, and function of nerve and brain tissues, cell membranes, and organs. Docosahexaenoic acid (DHA) plays a role in cognitive development and visual acuity. Avoidance of dietary fat in women with AN or BN has been documented [26, 27]. This has implication for overall energy intake as well as absorption, metabolism, and utilization of fat-soluble vitamins.

Balanced energy intake is critical to adequate weight gain and micronutrient availability during pregnancy. In general, total energy intake should be made up of 45-65% carbohydrate, 10-35% protein, and 20-35% lipids or dietary fat [28].

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