Effect of weekly high-dose vitamin D3 supplementation on the association between circulatory FGF-23 and A1c levels in people with vitamin D deficiency: A randomized controlled 10-week follow-up trial

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Sara M. Alimam
Jehad F. Alhmoud
Heba A. Khader
Ahmad R. Alsayed
Mohammad Abusamak
Beisan A. Mohammad
Ibrahim Mosleh
Khalid Abu Khadra
Ahmad Aljaberi
Maha Habash
Luai Hasoun
Mahmoud S. ABU-SAMAK


vitamin D deficiency, vitamin D3, fibroblast growth factor-23, A1c, OSC


Purpose: This randomized clinical trial (RCT) was designed to assess the effect of vitamin D supplementation (VD3) on the relationship between the levels of fibroblast growth factor-23 (FGF-23) and osteocalcin factor (OSC) with glycated hemoglobin (A1c) values in the blood in a sample of Jordanian males and female adults with vitamin D deficiency. Subjects and methods: This RCT was designed to randomly split (78) eligible participants into two groups: experimental (Group A) and interventional (Group B). Group B was supplemented with a weekly dose of 50,000 IU VD3 for eight weeks. Fasting baseline and follow-up (10 weeks; 8 weeks supplementation plus washout two weeks) of serum 25 hydroxyvitamin D (25OHD), fibroblast growth factor-23, (FGF- 23), glycosylated hemoglobin (A1c), parathyroid hormone (PTH), calcium, and phosphorus were assayed. A paired T-test was used to assess the changes in fibroblast growth factor-23, A1c, and OSC levels over the follow-up period. RESULTS: Significant increase in follow-up level of 25OHD (40.04 ± 11.61 vs. 15.35 ± 5.41, PC < 0.001), FGF-23 (114.04 ± 103.8 vs. 87.40 ± 82.21, PA = 0.02) and A1c (5.63 ± 0.33 vs. 5.38 ± 0.32, PA = 0.01). Conclusion: High doses of vitamin D supplementation (50,000 IU/week) may have potentially negative effects on glycemic control, which might be related to changes in serum osteocalcin than in FGF23 levels.

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