Not surprising the results were only modest, given that only 400 I.U.s of Vit. D were given. Other research studies include 800 - 1200 I.U.'s of Vit. D, along with other co-factors for calcium absorption such as Vit. K and Magnesium:

http://www.timesreporter.com/left.php?ID=50765&r=5

Here's a study showing the benefits of magnesium in the care of osteoporosis, although among blacks there is apparently factors that limit that effectiveness:

http://www.ncbi.nlm.nih.gov/en...&itool=pubmed_docsum