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Nutritional Requirements Throughout the Life Cycle: Pregnancy and Lactation

Pregnant and lactating women have increased requirements for both macronutrients and micronutrients. The failure to achieve required intakes may increase risk for certain chronic diseases in their children, sometimes manifesting many years later.10,11 For instance, studies of the Dutch famine during World War II (in which rations were progressively cut from 1,400 kcal/day in August 1944 to 1,000 kcal/day in December, and ultimately to 500 kcal/day) found that undernutrition during mid– to late pregnancy increased the risk for glucose intolerance and resulted in greater progression of age–related hypertension.27 Malnutrition of women during early pregnancy correlated with higher body weights of their offspring as adults, along with increased risk for coronary heart disease and certain central nervous system anomalies.10,27,28

Protein requirements in pregnancy rise to 1.1 g/kg/day (71 g), amounting to more than a 50% increase in protein intake to allow for fetal growth and milk production. The source of protein may be as important as the quantity, however. Some evidence suggests that protein requirements can be more safely met by vegetable than by animal protein. Meat is a major source of saturated fat and cholesterol; it is also a common source of ingestible pathogens29 and a rich source of arachidonic acid, a precursor of the immunosuppressive eicosanoid PGE2.

Pregnant women also should not meet their increased need for protein by the intake of certain types of fish, such as shark, swordfish, mackerel, and tilefish, which often contain high levels of methylmercury, a potent human neurotoxin that readily crosses the placenta.30 Other mercury–contaminated fish, including tuna and fish taken from polluted waters (pike, walleye, and bass), should be especially avoided.31 There is no nutritional requirement for fish or fish oils. Vegetable protein sources, aside from meeting protein needs, can help meet the increased needs for folate, potassium, and magnesium and provide fiber, which can help reduce the constipation that is a common complaint during pregnancy.

Pregnant and/or lactating women also require increased amounts of vitamins A, C, E, and certain B vitamins (thiamine, riboflavin, niacin, pyridoxine, choline, cobalamin, and folate). Folate intake is especially important for the prevention of neural tube defects and should be consumed in adequate amounts prior to conception; evidence shows that average intakes are only ~60% of current recommendations.32 Folate intakes were noted to be poorest in women eating a typical Western diet and highest in women eating vegetarian diets.33 Pregnant women also require increased amounts of calcium, phosphorus, magnesium, iron, zinc, potassium, selenium, copper, chromium, manganese, and molybdenum.1 Prenatal vitamin–mineral formulas are suggested to increase the likelihood that these nutrient needs will be met.

 

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