Objective: This study aims to prospectively assess the incidence of hypercalciuria and hypercalcemia with different doses of vitamin D and with a calcium intake of approximately 1,200 mg/day.
Methods: This was a 1-year randomized placebo-controlled study of vitamin D (400-4,800 IU/d) in 163 white women aged 57 to 90 years. Calcium citrate tablets (200 mg) were added to the diet to achieve a total calcium intake of approximately 1,200 mg/day in all groups. All women had vitamin D insufficiency at baseline, with serum 25-hydroxyvitaminD levels lower than 20 ng/mL (50 nmol/L). Serum and 24-hour urine calcium were collected every 3 months on supplementation, any test result above the upper reference range represented an episode of hypercalcemia or hypercalciuria. Mixed-effects models and multivariate logistic regression were used in the analysis.
Results: Hypercalcemia (>10.2 mg/dL [2.55 mmol/L]) occurred in 8.8% of white women. Hypercalciuria (>300 mg/d [7.5 mmol]) occurred in 30.6% of white women. Episodes of hypercalciuria were transient in half of the group and recurrent in the other half. No relationship between hypercalcemia or hypercalciuria and vitamin D dose was found, and hypercalciuria was equally common in the placebo group.
Conclusions: Hypercalciuria and hypercalcemia commonly occur with vitamin D and calcium supplements. Whether hypercalciuria and hypercalcemia are caused by calcium, vitamin D, or both is unclear. These findings may have relevance to the reported increase in kidney stones in the Women’s Health Initiative trial. Because calcium 1,200 mg and vitamin D 800 IU/day are widely recommended in postmenopausal women, systematic evaluation of the safety of supplements is warranted in clinical management and in future studies.
From the 1Bone Metabolism Unit, Creighton University, Omaha, NE; and 2College of Public Health, University of Nebraska Medical Center, Omaha, NE.
Received December 19, 2013; revised and accepted April 9, 2014.
Funding/support: This study was supported by grant AG28168 from the National Institute on Aging and Office of Dietary Supplements.
Clinical trial registration: NCT00472823.
Financial disclosure/conflicts of interest: J.C.G. received at no cost calcium supplements from Bayer HealthCare for this study. The other authors report no conflicts of interest.
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Address correspondence to: John Christopher Gallagher, MD, Creighton University Medical Center, Suite 6718, 601 North 30th Street, Omaha, NE 68131. E-mail: email@example.com; firstname.lastname@example.org