To investigate the impact of two vitamin D doses, bracketed between the IOM recommended dietary allowance (RDA) and the upper tolerable limit, on vitamin D nutritional status in elderly individuals.This is a post-hoc analysis on data collected from a 12-month, double-blinded, randomized control trial. 221 ambulatory participants (≥ 65 years), with a mean BMI of 30.2 kg/m 2, and a mean baseline serum 25-hydroxyvitamin D [25(OH)D] level of 20.4 ± 7.4 ng/ml, were recruited from 3 out-patient centers in Lebanon. They all received 1,000 mg of elemental calcium from calcium citrate daily, and the daily equivalent of 600 IU or 3,750 IU, of vitamin D3.Mean 25-hydroxyvitamin D [25(OH)D] level at 12 months was 26.0 ng/ml with low dose and 36.0 ng/ml with high dose, of vitamin D3. The proportion of participants reaching a value ≥ 20 ng/ml was 86% in the low dose, and 99% in the high-dose arms, with no differences between genders. The increment of 25(OH)D per 100 IU/day was 1ng/ml with the low dose, and 0.41 ng/ml with the high dose. Serum 25 (OH)D levels at 1 year were highly variable in both treatment arms. Baseline 25(OH)D level and vitamin D dose, but not age, BMI, gender, nor season, were significant predictors of serum 25(OH)D level post-intervention.The IOM RDA of 600 IU/day does not bring 97.5% of ambulatory elderly individuals above the desirable threshold of 20 ng/ml. Country-specific RDAs are best derived taking into account the observed variability and predictors of achieved 25(OH)D levels.
Dania S Bacha, Maya Rahme, Laila Al-Shaar, Rafic Baddoura, Georges Halaby, Ravinder J Singh, Ziyad R Mahfoud, Robert Habib, Asma Arabi, Ghada El-Hajj Fuleihan