Evaluation of the Bioavailability of Vitamin D2 in Yeast and Bread

Vitamin D helps in reducing the risk for the development of many chronic diseases. Humans get vitamin D mainly from direct exposure to sunlight, from diet, or from dietary supplements. The bioavailability of vitamin D from dietary supplements has been tested. In one study, subjects had initial vitamin D level of less than 10ng/ml, and it rose to 60ng/ml 24 hours after taking a vitamin D supplement capsule that contained 50,000 IU of vitamin D2. Food contains vitamin D2 or vitamin D3 either naturally or after being fortified. Fortification of dietary products date back to the first half of the 20th century when Steenbock discovered that irradiation of food helped in promoting the healing of rickets in vitamin D deficient rachitic rats. Since that time, companies started to fortify their products to enhance their vitamin D content. In the 1930s Bond Bread fortified its bread with vitamin D2. Recently the FDA approved yeast vitamin D2 which is a yeast that was exposed to ultraviolet radiation. This yeast is active and when used to raise bread the bread contains vitamin D2. The baking process does not affect the vitamin D content. What is unknown is whether the vitamin D2 that is produced in the bread is bioavailable. The purpose of this study is to determine the bioavailability of vitamin D2 that is present in yeast, in bread that was raised with vitamin D2 yeast and vitamin D2 in the cell walls of yeast compared to a vitamin D2 supplement and a vitamin D3 supplement.