Lactation is nutritionally demanding, especially for the mother who nurses her infant exclusively for a number of months.
Milk production is most affected by the frequency of suckling and maternal hydration. Milk composition varies according to the mother’s diet. Breast milk of malnourished mothers has been shown to have lower levels of various nutrients, reflecting the foods available to eat.
Milk production is 80% efficient – production of 100 ml breast milk (75 kcal) requires 85 kcal expenditure. During the first 6 months of lactation, average milk production is 750 ml/day, with a range of 550 to more than 1200 ml/day. The DRI for energy during lactation is 330 kcal greater during the first 6 months of lactation and 400 kcal greater during the second 6 months of lactation over that for a not pregnant woman. It is the same as the RDA during the second trimester of pregnancy. The obese and overweight woman may not require the full 330 to 400 extra calories a day. Maternal fat stores accumulated during pregnancy provide about 100 to 150 kcal to support the early months of lactation. When the reserve fat stores have been depleted, dietary energy support for lactation must be increased if the mother intends to provide all or most of her infant’s nutrition through breast milk alone. During the second 6 months of lactation, production generally drops to an average of 600 ml/day (20 oz/day).
Milk production decreases in mothers who undertake rigorous calorie-restricted diets (under 1500 kcal). It is advisable for lactating women to maintain an energy intake of at least 1800 kcal/day. Healthy breast-feeding women usually can lose as much as 1 lb/week and still supply adequate milk to maintain their infant’s growth. Appropriate fluid intake and adequate rest are also needed. Overweight lactating women can restrict their energy intake by 500 kcal a day by decreasing consumption of foods high in fat and simple sugars, but they must increase their intake of food high in calcium and vitamin D, especially from fruits and vegetables.
Breast-feeding woman should get an additional 25 g of protein a day, or 71 g of protein a day.
To maintain appropriate blood glucose and prevent ketonemia during lactation, 160 to 210 g/day of carbohydrates are recommended.
The amount and type of fat in breast milk directly reflects the maternal diet. There is no DRI for total lipids during lactation since it depends on the amount of energy required by the mother to maintain milk production.
The calcium content of breast milk is not related to maternal intake, and there is no convincing evidence that maternal change in bone mineral density is influenced by calcium intake across a broad range of intakes up to 1600 mg/day. Maternal bone loss during lactation is 3-7%, which is rapidly regained after weaning. The AI for calcium during pregnancy and lactation and in females who are not pregnant or lactating is 1300 mg/day for women less than 19 years old, 1000 mg/day for 19-50 year old women.
The vitamin D content of milk is related to maternal vitamin D intake and the degree of sun exposure. Women with lactose intolerance who do not drink vitamin D-fortified milk or take a vitamin supplement may be at higher risk for vitamin D deficiency. The AI for vitamin D during lactation is 5 mcg/day. Also is recommended that all infants receive an additional 5 mcg of vitamin D daily beginning at 2 months of age.
The requirements for zinc during lactation are greater than those during pregnancy. In the process of normal lactation the zinc content of breast milk drops dramatically during the first few months from 2 to 3 of mg zinc a day to 1 mg/day by the third month after birth. In zinc deficient-lactating women, normal zinc concentrations are maintained in breast milk for at least the first 2 months of lactation. The DRIs for zinc during lactation are 12 to 14 mg/day.