Absurdity of 600 IU vitamin D for 10 lb infant or 300 lb adult
Heart Scan Blog had image of a 270 lb man in diapers
clip - - - -
^It would be like trying to fit a large, full-grown man into the diapers of a 13-month old.
Few nutrients or hormones (in fact, I can't think of a single one) are required in similar quantity by an infant or toddler and a full grown adult. ^
Need to add vitamin D for each of the following reasons

Unhealthy people need even more vitamin D
And - the blood levels vary by 4X between individuals.
Details at VitaminDWiki
Overview Moms babies and vitamin D not even mentioned above
Recommendations of vitamin D IU and ng around the world US is NOT the worst!
An official reviewer of the IOM vitamin D report makes his opinion known – Jan 2011
Dose response equation 427(1+pigmentation grade)10-2 +(dose IU/day)*10-2/Body massindex,
The folly of RDA for vitamin D - Jan 2011 same author - HeartScanBlog
IU vs Age (and done poorly, at that) - by I o M

Vitamin D deficiency is a complex topic
