Session: OR45-What Is New in Vitamin D?
Room 29 (San Diego Convention Center)
Outstanding Abstract Award
METHODS:We conducted two randomized, placebo-controlled trials in women with vitamin D insufficiency (serum 25-hydroxyvitamin D ≤20 ng/dl [50 nmol/liter]). In the older group (273 Caucasian and African American women) the age range was 57-90 years. In the younger women (198 Caucasian and African American) the age range was 25–45 years and. Older women were randomly assigned to placebo, vitamin D3 400, 800, 1600, 2400, 3200, 4000, or 4800 IU daily; calcium supplements were given if needed to maintain a total daily calcium intake of 1200-1400 mg/day. Younger women were randomized to placebo, 400, 800, 1600 and 2400IU/d and calcium intake maintained at 1000mg/day. The average calcium supplement in older women was 600mg and in younger women was 340mg.
Serum and 24-hour urine calcium were collected every 3 months; any test result above the laboratory upper normal range represented an episode of hypercalcemia or hypercalciuria (24h urine calcium >300 mg /24 hour in Caucasians and >270 mg/24 hour in African Americans). Calcium absorption was measured by a single isotope Ca45 method. Mixed-effects models were used to estimate the effects of time and dose on urine and serum calcium.
RESULTS:In the older women, hypercalcemia occurred in 8.8% of Caucasian and 7% of African American women. In the younger women, hypercalcemia occurred in 1% of African American women and 0% of Caucasian women. In older women hypercalciuria occurred in 30.6% of Caucasian and 15% of African American women. In younger women hypercalciuria occurred in 20% of Caucasian and 15% of African American vitamin D treated women. In the placebo group that received only calcium, hypercalcemia occurred in 2.7% and hypercalciuria in 21 % occurred in the placebo group. In both studies no relationship was found between episodes of hypercalcemia or hypercalciuria and vitamin D3 dose or serum 25OHD level. Calcium absorption was measured in the younger women. It was normal in all women and 4% lower in African Americans. There was a small decrease in bone resorption marker N-telopeptide.
CONCLUSION: The risks of hypercalcemia and hypercalciuria are higher in Caucasian women compared to African Americans and higher in older women. The risk is not related to the vitamin D dose, serum 25OHD level, calcium absorption or bone resorption. Even in the placebo group on a total daily calcium intake of 1200 or 1000 mg there is an increased risk of hypercalcemia and hypercalciuria; thus, even a modest calcium supplementation of 350 in young or 600mg/day in older women may be too high.
Nothing to Disclose: SHT, JCG, SY, VY
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