The nutritive demands of lactation are considerably greater than those of pregnancy. In the first 4-6 months of the postpartum period, infants double their birth weight accumulated during the 9 month of pregnancy.
Currently at UCC a study investigating the significance of supplementing vitamin D, calcium and vitamin K to lactating mothers in order to improve their vitamin D status, the nutritional value of their breast milk and to assist with the normalization of body weight after pregnancy. For more information see D-MUMS
Vitamin D content in breast milk
There is no doubt that breast milk is the best feeding option for infants between birth and 6 months. However, breast milk is not a good source of vitamin D. Literature reports a range of concentrations for the level of vitamin D in breast milk, varying from 0.1 to 1.2µg/l, but the British Food composition tables (Holland et al. 1989) report a value 0.4µg/l. Seasonal variation is also observed in the vitamin D activity of human milk where activity is lower in winter compared to the summer. Most studies agree that exclusively breast-fed infants have a reduced vitamin D status after 6 weeks of age if no supplemental vitamin D is given. A recent study with high dose vitamin D3 supplementation for 6 months in a cohort of breastfeeding mothers and their infants showed 160µg vitamin D3/day to safely and significantly increase both maternal 25(OH)D concentrations and antirachitic activity of their milk, whereas supplementation of 10µg vitamin D3/day (the current AI) failed to maintain both maternal 25(OH)D concentrations or antirachitic activity of their milk (Wagneret al, 2006). A recent report (FSAI, Mar 2007) has recommended implementing a national policy of vitamin D supplementation in all infants aged 0-12 months in Ireland.