This is an open-labelled, randomized controlled clinical trial aimed to compare the pharmacokinetics of an orodispersible vs a soft gelatin vitamin supplementation in vitamin D deficient healthy adults.

Vitamin D is a fat-soluble vitamin used by the body for normal bone development and maintenance by increasing the absorption of calcium, magnesium, and phosphate. Vitamin D also plays a role in the nervous system, musculoskeletal system and immune system. Vitamin D deficiency has been linked with diverse health conditions including diabetes, cardiovascular diseases, breast, colorectal and prostate cancer, dementia, depression, erectile dysfunction, osteoporosis, and bone disorders. Vitamin D deficiency is a global healthcare challenge. To overcome vitamin D deficiency, a daily vitamin D supplementation of 200-1000 IU or a high dosage from 25000 to 200000 IU for 4-6 weeks, is normally recommended.

Vitamin D supplements are available over the counter in different delivery vehicles (formulations) to reach the circulatory system. In the present study the investigators aim to evaluate the pharmacokinetics of an orodispersible vitamin D supplement vs a conventional oral soft gelatin capsule, in vitamin D deficient healthy adults to assess how different vitamin D supplement formulations can efficiently overcome the vitamin D deficiency.

Inclusion Criteria:

• Healthy male and female adults aged 18 - 60 years
• Vitamin D deficiency as shown by serum levels of 25 (OH) D3 levels of < 20 ng/mL
• Able to provide informed written consent

Exclusion Criteria:

• Clinically significant abnormal laboratory parameters (such as complete blood count, CRP, d-dimer, liver enzymes, creatinine) indicative of physical illness, especially hypercalcemia and hypercalciuria
• History of hypersensitivity to vitamin D3 supplements
• History of renal, hepatic, gastrointestinal, cardiovascular, respiratory, skin, haematological, endocrine, or neurological diseases
• Prior use of medications in general containing calcium, magnesium, or vitamin D3, four weeks before the start of the study
• Participation in the evaluation of any investigational product or blood donations in the last three months before this study
• Any other significant disease or disorder that, in the opinion of the Physician, may either put the participant at risk because of participation in the study, or may influence the results of the study, or the participant's ability to participate in the study