The Effect of a Meal on Vitamin D Absorption

This study seeks to determine if vitamin D3 absorption in healthy adults will be enhanced in the presence of a meal and if the enhancement will be greater when the meal is low as opposed to high in fat content. The enhancement will result from increased vitamin D absorption. The investigators will test this hypothesis by pursuing the following aims in a 3-mo trial in which up to 70 healthy men and women will be randomized to one of the following meal conditions under which they will take a monthly oral dose of 50,000 IU of vitamin D3: no meal (fasting), a low fat meal, or a high fat meal. The Primary Aim is to identify the meal condition (fasting, low-fat, or high-fat meal) under which the 25OHD3 response to supplemental vitamin D3 is greatest and most consistent. The Secondary Aim is to determine whether vitamin D3 absorption is affected by the meal condition and to determine whether the absorption of vitamin D3 predicts the longer-term 25OHD3 response to supplementation.