When was your Serum 25-hydroxyvitamin D Concentration Measured?
The Institute of Medicine (IOM) updated Dietary Reference Intakes (DRIs) for vitamin D and calcium in 2010. At the time, the vitamin D Recommended Dietary Allowances (RDAs) were increased to 600 IU daily for all age groups except those over 70y which were set to 800 IU. Estimated Average Intakes (EARs) and RDAs were based on serum 25(OH)D concentrations of 40 and 50 nmol/L, respectively. The Upper Tolerable Limit (UL) for adults was set at 4,000IU.
In a new study, Veugelers and associates aggregated data from 36 studies with 108 study dose estimates and 13,987 observations (participants). Their model calculates a daily intake of 2,909 IU vitamin D is needed daily to maintain serum 25-hydroxyvitamin D concentrations of ≥50 nmol/L in 97.5% of healthy individuals. This intake recommendation is anticipated to have 2.5% of the population with serum 25-hydroxyvitamin D concentrations exceeding 200 nmol/L.
This research team has previously argued that a statistical error was made in calculating the 2010 RDIs. Serum 25-hydroxyvitamin D concentrations increase with increasing intake. The impact of supplementation is greater at lower intake, 12 nmol/L per 1,000 IU with supplementation levels between 0 to 1,000 IU daily, and dropping to ~1 nmol/L per 1,000 IU as vitamin D supplementation increases to 20,000 IU daily. Overweight and obese individuals, on average, have serum 25(OH)D concentrations that are 19.8 to 8.0 nmol/L, respectively, at similar intakes. People with extra central adiposity (abdominal fat) are the most likely to have lower serum 25(OH)D concentrations.
This new study will stimulate debate regarding vitamin D requirements. In reality, because each of us is different, individuals cannot find their answer using the law of averages and primary estimates of variability. The only assurance is to measure serum 25(OH)D and adjust our vitamin D intake (or sun exposure) to maintain serum 25(OH)D concentrations ≥50 nmol/L.
Veugelers PJ, Pham T-M, Ekwaru JP. Optimal vitamin D supplements doses that minimize both low and high serum 25-hydroxyvitamin D concentrations in the general public. 2015 Nutrients doi: 10.3390/nu7125527
Veugelers PJ, Ekawaru JP. A statistical error in the estimation of the recommended dietary allowance for vitamin D. 2014 Nutrients doi: 10.3390/nu6104472
Ekwaru JP, Zwicker JD, Holick MF, Giovannucci E, Veugelers JP. The importance of body weight for the dose response relationship of oral vitamin D supplementation and serum 25-hydroxyvitamin D in healthy volunteers. 2015 PLoS ONE doi: 10.1371/journal.pone.0111265
Zhang M, Li P, Zhu Y, Chang H, Wang X, Liu W, Zhang Y, Huang G. Higher visceral fat area increases the risk of vitamin D insufficiency and deficiency in Chinese adults. 2015 Nutr Metab doi: 10.1186/s12986-015-0046-x