Baseline levels determine magnitude of increment in 25 hydroxy vitamin D following vitamin D3 prescription in healthy subjects.

INTRODUCTION: Vitamin D deficiency is a major health problem which affects about one billion people in the world. Although, vitamin D supplementation is recommended as standard treatment of vitamin D deficiency, there are controversies on dose response relationship. In this regard, the present study aimed to determine the impact of vitamin D3 supplement on raising of serum 25 hydroxyvitamin D[25(OH)D] in healthy subjects with varying degrees of vitamin D deficiency.

MATERIALS AND METHODS: In this clinical trial 114 subjects with varying degrees of vitamin D deficiency were entered and divided into three groups: serum levels of 25(OH) D less than 10 ng/ml, 10-20 ng/ml, and 20-30 ng/ml. All of the participants were given 50,000 units vitamin D3 per week for 8 weeks, thereafter, changes in serum levels of vitamin D and PTH were evaluated at week twelve. The results were analyzed using SPSS version 16 and P < 0.05 was considered to be significant.

RESULTS: Of the 114 vitamin D deficient subjects, serum level of vitamin D was below 10 ng/ml in 22 persons (19.3%), 10-20 ng/ml in 52 persons (45.6%) and 20-30 ng/ml in 40 persons (35.1%). Following vitamin D prescription all people with varying degrees of vitamin D deficiency obtained a favorable serum level. The increase in vitamin D levels were 26.4, 18.5, and 8.3 ng/ml, in individuals with baseline vitamin D levels below 10 ng/ml, 10-20 ng/ml and 20-30 ng/ml, respectively. The changes in 25(OH) vitamin D in all three groups were significant (P < 0.05), nonetheless no significant alterations in serum levels of PTH were observed (P > 0.05).

CONCLUSION: Our results indicated an inverse relationship between baseline serum levels of 25(OH) D and its increment following treatment with vitamin D3. Therefore, the magnitude of increments in serum 25(OH) D is greater in subjects with lower baseline levels of 25(OH) D.