In a double blind, randomized trial, our objective was to assess the effect of high temperature pizza baking on the bioavailability of vitamin D3 fortified Mozzarella cheese. We tested the following hypotheses, set a priori: 1) vitamin D3 is bioavailable from pizza baked with fortified Mozzarella cheese and heat does not significantly break down vitamin D3; and 2) the change in serum 25(OH)D (from baseline to 10 wk) will be significantly greater in the high-dose vitamin D treated group (28000 IU/wk) compared to the low dose vitamin D-treated group (200 IU/wk).