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Open Access Thesis

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Degree Program


Degree Type

Master of Science (M.S.)

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Month Degree Awarded



Vitamin D deficiency is an epidemic issue in all age groups in Western countries and that affects both skeletal and non-skeletal functions. Even with the wide application of food fortification, vitamin D deficiency tends to increase continuously. Being hydrophobic in nature, vitamin D has poor solubility; thereby it negatively affects its absorption and bioavailability when compared to other hydrophilic dietary compounds. The need to develop a novel strategy is of greater importance to enhance its bioavailability and thereby improving vitamin D level in the body.

In this study, lipid-based delivery of oil-in-water nanoemulsion (diameter < 200nm) was utilized to improve the bioaccessibility and oral bioavailability of vitamin D3. First, we examined the in vitro relative bioaccessibility of nanoencapsulated vitamin D3 using a simulated gastrointestinal system. The study results showed that nanoemulsion-based delivery system significantly increased the relative bioaccessibility by 3.94 fold when compared to the coarse emulsion (diameter >200nm), as indicated by the concentration of vitamin D3 in the mixed micelles.

To evaluate the in vivo bioavailability of vitamin D3 an animal study was conducted. Mice were assigned randomly to three groups: vitamin D3 nanoemulsion (n=6), coarse emulsion (diameter > 200nm) (n=6) and vehicle (nanoemulsion without vitamin D3) (n=3), which is the control group. After 3-days of feeding emulsion by mixing in drinking water, the serum 25(OH)D3, a biomarker of vitamin D availability, was measured using immunoassay. We found that serum 25(OH)D3 level in animals fed with vitamin D3 nanoemulsion was significantly higher than in those animals fed with coarse emulsion (22.7 ± 1.10 ngmL-1 vs 17.92 ± 2.82 ngmL-1). It indicated that nanoemulsion improved the in vivo bioavailability by 28%. These results showed that the nano-based delivery systems can be utilized to improve vitamin D level, and further human studies are warranted for its application to the human population in order to improve the vitamin D status.


First Advisor

Zhenhua Liu

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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