Vitamin D3 Dose Requirement That Raises 25-Hydroxyvitamin D to Desirable Level in Overweight and Obese Elderly

Context: Guidelines for the dosage of vitamin D supplementation vary widely globally. Objective: To investigate the impact of 2 vitamin D doses, bracketed between the IOM recommended dietary allowance (RDA) and the upper tolerable limit, on vitamin D nutritional status in elderly individuals. Methods: This post hoc analysis of data collected from a 12-month, double-blind, randomized control trial included 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, who were recruited from 3 outpatient centers in Lebanon. All participants received 1000 mg of elemental calcium daily from calcium citrate plus the daily equivalent of either 600 IU or 3750 IU of vitamin D-3. Results: Mean 25(OH)D level at 12 months was 26.0 ng/mL with low dose and 36.0 ng/mL with high dose vitamin D-3. 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 gender differences. The increment of 25(OH)D per 100 IU/day was 1 ng/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, or season-were significant predictors of serum 25(OH)D level post-intervention. Conclusion: The IOM Recommended Dietary Allowance (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.