Effect of fat on serum 25-hydroxyvitamin D levels after a single oral dose of vitamin D in young healthy adults: a double-blind randomized placebo-controlled study

This double-blind placebo-controlled trial evaluated serum 25-hydroxyvitamin D [25(OH)D] levels after the oral intake of a single dose of cholecalciferol during one of the three meals, containing different amounts of fat or placebo. Sixty-four healthy medical residents or students of a university hospital in Porto Alegre, latitude 30A degrees S, Brazil, were divided into four groups. Three groups received a single 50,000 IU oral dose of cholecalciferol during a meal containing 0 g (Group 1), 15 g (Group 2) or 30 g (Group 3) of fat, and one group received placebo (Group 4), according to randomization. Serum 25(OH)D, parathyroid hormone, total calcium, albumin, magnesium, and creatinine levels, and urinary calcium, magnesium, and creatinine levels were measured at baseline and after 14 days. Baseline mean serum 25(OH)D levels were low in all groups. Vitamin D given during breakfast increased the mean change of serum 25(OH)D levels, when compared to placebo. Furthermore, the intake of fat with vitamin D increased the mean change of serum 25(OH)D levels. A single oral dose of vitamin D given with food increased mean serum 25(OH)D levels, after 2 weeks, and the mean increase was larger, when the meal had at least 15 g of fat. These findings can have important implications to oral vitamin D supplementation.