Vitamin C nutrition during prolonged lactation: optimal in infants while marginal in some mothers.

Prolonged breast-feeding is practiced by mothers in the hope of improving their infants' health and preventing diseases. In this study of the nutritional adequacy of breast-feeding, 200 mothers with healthy, full term newborns were encouraged to breast-feed exclusively. At age 6 months 116 infants and at age 9 months 36 infants remained exclusively breast-fed. The control infants were weaned early and they received vitamin C through a supplemented milk formula and solid food. The exclusively breast-fed infants were able to maintain their plasma vitamin C concentration at the same or a higher concentration than the vitamin C-supplemented controls. Their plasma concentration was about 2-fold compared with the maternal concentration. It was relatively independent of maternal nutrition and of vitamin C concentration in milk. The mother's intake of vitamin C influenced their plasma and milk concentrations. About 6% of the mothers had subnormal plasma concentrations without symptoms. The lowest concentrations occurred 2 months postpartum and during the spring. Thus, exclusively breast-fed infants are well protected against vitamin C deficiency, but marginal intake in lactating mothers is more common than assumed for a well-nourished population.