There are several million people worldwide with various fat malabsorption syndromes including those who have undergone gastric bypass surgery and those with obesity. These patients often have a difficult time absorbing vitamin D and both groups of patients are at an increased risk for vitamin D deficiency and therefore at higher risk for osteoporosis and osteomalacia (softening of the bones). Patients with obesity are also susceptible to vitamin D deficiency as vitamin D derived from intestinal absorption and cutaneous synthesis is diluted in a larger body pool of fat. Now a new study demonstrates 25-hydroxyvitamin D3 is an effective treatment for vitamin D deficiency for these specific patients.