Evaluation of vehicle substances on vitamin D bioavailability: a systematic review.

Vitamin D insufficiency is a common medical condition. Vitamin supplements can be ingested to improve vitamin D status. It is not known if the vehicle substance that is combined with the vitamin D tablet influences the bioavailability of vitamin D. The purpose of this review is to examine the impact of different vehicles on vitamin D bioavailability. A comprehensive literature search identified studies that directly compared the absorption of vitamin D from two or more vehicles. The change in mean serum 25(OH)D per average daily dose of vitamin D supplemented was calculated and compared among the studies. We identified four clinical studies that compared two different vehicles of vitamin D. Vitamin D in an oil vehicle produced a greater 25(OH)D response than vitamin D in a powder or an ethanol vehicle in healthy subjects. There are limited studies that have compared the influence of the vehicle substance on vitamin D bioavailability. Future studies should examine bioavailability among different vehicle substances such as oil, lactose powder, and ethanol and examine if there are any differences in bioavailability among different patient populations including those with fat malabsorption.