The big problem here is that no one actually really knows just how much vitamin D is necessary. So their claims of X units per day recommended are just as bogu

The big problem here is that no one actually really knows just how much vitamin D is necessary. So their claims of X units per day recommended are just as bogus as those claiming 2X or 3X. Until we can actually figure out just where all that vit D is supposed to be used in the body, we're just making it up. (It should be noted that this study only seems concerned with bone growth-- something we are not sure of yet is vitamin D's only function)