High Dose Vitamin D Supplementation in the Presence of Calcium Intake at the IOM Upper Level  

Presentation Number: OR07-3
Date of Presentation: April 2nd, 2017

Subhashini Katumuluwa*1, Shahidul Islam1, Mageda Mikhail1, Gianina Lucia Usera2, Alexandra Stolberg1 and John F Aloia1
1Winthrop University Hospital, 2North Shore-LIJ Health System

Abstract

Currently, the IOM has designated the tolerable upper level (UL) for vitamin D as 4,000 IU/day, while the Endocrine Society has suggested that up to 10,000 IU/day is safe. The level of 10,000 IU/day has not been studied extensively in RCTs, and not all prior studies of this value have reported on calcium intake or urinary calcium excretion. Furthermore, the 10,000 IU/day dose has not been explicitly studied in combination with the calcium UL dose, as recommended by the IOM, of 2,000 mg/day.

This was a one year randomized double-blind clinical trial that compared the effects of 10,000 IU/day vitamin D (Endocrine Society suggestion) plus 2,000 mg/day calcium (IOM UL) versus 600 IU/day vitamin D (IOM RDA) plus 2,000 mg/day calcium on the incidence of hypercalciuria and hypercalcemia in 132 postmenopausal Caucasian women age 50 and older. Serum and urinary calcium levels were assessed at baseline and at three-month intervals. For analysis, hypercalciuria was designated as a 24-hour urinary calcium excretion higher than 250 mg, and hypercalcemia as a serum calcium higher than 10.2 mg/dL.

Based on 24-hour urine results, there was a 79% increased risk of developing at least one hypercalciuric episode during the study in subjects who received 10,000 IU/day vitamin D compared to subjects who received 600 IU/day (RR(95% CI)=1.79(1.15-2.79); p = 0.013). In the 10,000 IU/day group, total urine calcium increased to 219 mg/day at 12 months from a baseline of approximately 127 mg/day, while in the 600 IU/day group, total urine calcium increased to 169 mg/day at 12 months from a baseline of 127 mg/day. There was no significant difference in incidence of hypercalcemia between the two groups (RR=1.36(0.68-2.7); p = 0.51). In the 10,000 IU/day group, serum calcium increased to 9.7 mg/dL at 12 months from a baseline of 9.5 mg/dL, while in the 600 IU/day group, serum calcium was 9.5 mg/dL both at baseline and 12 months.

Similar to a recent RCT1 and a meta-analysis2, our results show that episodes of hypercalciuria and hypercalcemia occur with vitamin D and concurrent calcium supplementation. Whether these two outcomes are due to vitamin D, calcium, or both cannot be concluded, as we had no placebo group. In contrast to both prior studies, we found a dose response relationship for vitamin D supplementation and incidence of hypercalciuria. Further studies of vitamin D supplementation at multiple doses, with and without concurrent calcium supplementation, compared to placebo are needed. Our results may also justify the value of regular monitoring of serum and urine calcium during vitamin D and/or calcium supplementation in the clinical setting.

 

Nothing to Disclose: SK, SI, MM, GLU, AS, JFA