2000 IU/day (400 as D₃ and 1600 as D₂). Group 2 Maternal supplement 4000 IU/day (400 as D₃ and 3600 IU as D₂).

Study 3: Group 1 Maternal supplement 400 IU D₃/day; infants received 300 IU D₃/day. Group 2 Maternal supplement 6400 IU D₃/day; infants received placebo.

vitamin D deficiency when sun exposure is limited. It is unknown whether such intake is adequate in dark-skinned infants in parts of the world where there is a high prevalence of severe vitamin D deficiency. There is also poor compliance with vitamin D supplementation of breastfeeding infants. The strategy of vitamin D supplementation of the breastfeeding infant does not address the concomitant high prevalence of vitamin D deficiency in their mothers. Maternal vitamin D supplementation of at least 2000 IU/day is required to provide a significant amount of vitamin D in the human milk for breastfeeding infants. Study 1 mothers who were supplemented with 2000 IU or 1000 IU had significantly higher 25(OH)D (p < 0.01). In Study 2, after 3 months of supplementation, the infants in the 2000 IU group had significantly lower serum 25(OH)D₂ levels than infants of mothers in the 4000 IU group (p = 0.003). In Study 3, after the 6 months of vitamin D supplementation, the mean ARA in milk was significantly higher in the 6400 IU group than the 400 IU group (p value not provided). Infants serum 25(OH)D were similar between groups: infants in the 400 IU group was 43 ug/L at the end of the study compared to 46 ug/L in the 6400 IU group. There was no evidence of toxicity in mothers or infants in either group.