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Nutrition During Lactation
Vitamin K. The vitamin K content of mature human milk is typically 2 µg/liter (Haroon et al., 1982), and that of colostrum is approximately twice as high (von Kries et al., 1987, 1988). When mothers with low vitamin K intakes are given 20-mg supplements of vitamin K in the form of phylloquinone, milk levels of the vitamin are increased by twofold for at least 48 hours (Haroon et al., 1982; von Kries et al., 1987). However, even when the mother's vitamin K intake from food has been high or she has routinely taken supplements containing vitamin K, the amount of this vitamin obtained by the breastfed neonate in the first few days after birth may be insufficient to meet the infant's needs (see Chapter 7).
Vitamin E. Approximately 83% of the total vitamin E content of human milk is α-tocopherol. Small quantities of β-, γ, and δ-tocopherols are present as well (Kobayashi et al., 1975). Concentrations of tocopherols are high in colostrum (8 mg/liter) and decline and stabilize to 2 to 3 mg/liter in mature human milk. A single case report indicates that high maternal intakes (approximately 27 mg of vitamin E per day) resulted in an elevated plasma concentration of α-tocopherol equivalents (3.8 mg/dl compared with a normal concentration of 0.5 to 2.0 mg/dl) and a high milk content of 11 mg/liter on day 38 of lactation (Anderson and Pittard, 1985).
Vitamin C. Bates and colleagues (1983) report that the vitamin C content of mature human milk levels off at 50 to 60 mg/liter if daily maternal intakes are equal to or exceed 100 mg (approximately the mother's Recommended Dietary Allowance [RDA] for this vitamin). When maternal vitamin C intake is relatively low, increases in intake are associated with an increased human milk content of this vitamin. These investigators also reported that the level of vitamin C in milk is 8 to 10 times that in maternal plasma.
Thiamin. There are large variations in the thiamin content of human milk between individuals and over the course of lactation. Thiamin concentrations are low in colostrum (10 µg/liter) and increase 7-to 10-fold in mature milk. Milk from mothers with beriberi contains less thiamin that that of healthy women in the same country. Infants nursed by mothers with beriberi develop the disease by 3 or 4 weeks of age (Hytten and Thomson, 1961). Pratt et al. (1951) have shown that the thiamin content of human milk can be sharply increased up to a certain limit, estimated to be 200 µg/liter.
Riboflavin and Niacin. Riboflavin content is high early in lactation and declines thereafter. The milk of well-nourished women contains riboflavin concentrations of approximately 350 µg/liter (Committee on Nutrition, 1985;