High-dose (6400 IU/day) vitD3 safely and significantly increased maternal circulating
25(OH)D and vitD from baseline compared to controls (p 0.0028 and 0.0043, respectively).
Mean milk antirachitic activity of mothers receiving 400 IU vitD/day decreased to a
nadir of 45.6 at visit four and varied little during the study period (45.6–78.6 IU/L), whereas
the mean activity in the 6400 IU/day group increased from 82 to 873 IU/L (p 0.0003). There
were no differences in circulating 25(OH)D levels of infants supplemented with oral vitD
versus infants whose only source of vitD was breast milk.