NOW Food's bestselling Calcium Citrate offers a lot more than just calcium citrate but falls a bit short of being a complete bone formula since it lacks vitamin K and boron. It does have the other critical nutrients for bone health, though. Magnesium at 300 mg per 2 tablet dose, from a combination of highly absorbable magnesium aspartate and not-so absorbable magnesium oxide. Trace elements zinc, copper and manganese are all in the desirable amino acid chelated form. Vitamin D is an important inclusion in any calcium formula, very safe, and very inexpensive from a manufacturing standpoint. Experts are recommending 1000-2000 IU a day for most people. Multis might provide 50-400 at the most. In light of that, NOW Calcium Citrate's 100 IU of vitamin D seems like a woefully small dose. Most multivitamins cannot supply the the full days supply of minerals in one dose, since calcium and magnesium alone require 3-4 tablets. Instead, they provide some calcium and magnesium and people use products like NOW's Calcium Citrate as a mineral booster to close the gaps. The few nutrients that it lacks in terms of bone health vitamin K and boron, are already supplied by most multis.