Effect of vitamin D supplementation on circulating fibroblast growth factor-23 concentration in adults with prediabetes

Background Recent meta-analyses report that vitamin D supplementation increases blood fibroblast growth factor-23 (FGF23) level.Objectives To determine the effect of 4000 IU/day of vitamin D-3 for 12 months on circulating FGF23 levels. We also examined the association of the achieved 25-hydroxyvitamin D level [25(OH)D] with the FGF23 level at 12 months and with 12-month changes in FGF23.Methods An ancillary analysis among adults 70 years and older with prediabetes who participated in a trial comparing vitamin D-3 4000 IU/day with placebo. Plasma intact FGF23 and serum 25(OH)D were measured at baseline and month 12 (M12).Results Characteristics of the 52 participants (vitamin D-3 n = 28; placebo n = 24) did not differ significantly aside from more women than men in the vitamin D-3 group. Mean +/- SD age was 73.8 +/- 3.7 years, BMI 31.3 +/- 4.2 kg/m2, and glomerular filtration rate (GFR) 76.3 +/- 11.8 mL/min/1.73m2 Baseline serum 25(OH)D level was 33.4 +/- 10.8 ng/mL and increased at M12 to 54.9 +/- 14.8 ng/mL in the vitamin D-3 group versus 33.4 +/- 14.9 in the placebo (p < 0.001). At baseline, GFR was inversely associated with FGF23 (r = - 0.349, p = 0.011). Change in FGF23 level at M12 did not differ significantly between vitamin D-3 and placebo. In all participants combined, the achieved serum 25(OH)D level at M12 was not significantly associated with the M12 plasma FGF23 or the M12 change in FGF23.Conclusion In obese older adults with sufficient vitamin D status and normal renal function, vitamin D-3 4000 IU/day for 12 months did not significantly alter plasma intact FGF23 levels. Clinicaltrials.gov NCT 01,942,694, registered 9/16/2013.

Automated summary

This study investigated the effect of 4000 IU/day of vitamin D-3 supplementation on blood fibroblast growth factor-23 (FGF23) levels. The results showed that vitamin D-3 supplementation did not significantly alter FGF23 levels in obese older adults.