There are approximately 40 milligrams (mg) of Vitamin C per liter of mature mothers' milk. The Vitamin C content of mother's milk increases with maternal levels, though studies strongly suggest that a regulatory mechanism is present.

In one study, Vitamin C leveled off at 50 to 60 mg per liter of milk once maternal intake reached OR exceeded the Recommended Dietary Allowance (RDA) for this vitamin (Bates, 1983). Another study also found the levels plateaued, to between 44 and 158 mg per liter of milk, even if the mother had been given 10 times the RDA for Vitamin C (Byerley, 1985).

Vitamin C levels in breastfed babies between the ages of 6 and 9 months were found to be the same or higher than in artificially fed controls (Salmenpera, 1984).

In colostrum, there is a slightly higher amount of Vitamin C than in mature breastmilk, averaging around 44 mg per liter of milk.

References:

• Nutrition During Lactation, Institute of Medicine, 1991.
• Bates et al. 1983. The effect of vitamin C supplementation on lactating women in Keneba, a West African rural community. Int J Vitam Nutr Res 53:68-76.
• Byerley LO & Kirksey A: Effects of different levels of vitamin C intake on the vitamin C concentration in human milk and the vitamin C intakes of breastfed infants. Am J Clin Nutr 41:665, 1985.
• Casey & Hambidge: Nutritional aspects of human lactation. Lactation, physiology, nutrition and breastfeeding, 1983.
• Salmenpera L: Vitamin C nutrition during prolonged lactation: optimal in infants while marginal in some mothers, Am J Clin Nutr 40:1050, 1984.