Evaluation of vitamin D3 intakes up to 15,000 international units/day and serum 25-hydroxyvitamin D concentrations up to 300 nmol/L on calcium metabolism in a community setting

ABSTRACT

Supplementation by the general public with vitamin D at doses above the Tolerable Upper Level of Intake (UL) is becoming quite common. The objective of the current analysis was to characterize the effect of vitamin D supplementation at doses up to 15,000 IU/d in a community-based program on vitamin D status, calcium homeostasis as well as on kidney, liver and immune function. We evaluated data collected for 3,882 participants in a community program for whom there were blood measurements at program entry and at follow-up within 6–18 months between 2013 and 2015. Participants were supplemented with a wide range of vitamin D doses (1,000 – 15,000 IU/d) aimed at achieving serum 25-hydroxyvitamin D [25(OH)D] levels of at least 100 nmol/L. Serum 25(OH)D concentrations up to 300 nmol/L were achieved without perturbation of calcium homeostasis or incidence of toxicity. Hypercalcemia and hypercalciuria were not related to an increase in 25(OH)D concentrations nor vitamin D dose. To achieve serum 25(OH)D levels >100 nmol/L on average, required vitamin D intakes of 6,000 IU/d for normal Body Mass Index (BMI), 7,000 IU/d for overweight and 8,000 IU/d for obese. Doses of vitamin D in excess of 6,000 IU/d were required to achieve serum 25(OH)D concentrations above 100 nmol/L, especially in individuals who were overweight or obese without any evidence of toxicity. Serum 25(OH)D concentrations up to 300 nmol/L were found to be safe.

KEYWORDS:

• 25-hydroxyvitamin D
• C reactive protein
• hypercalcemia
• hypervitaminosis D
• inflammation
• serum calcium
• supplementation
• toxicity
• vitamin D

ISRCTN:

• 18397898

Disclosure of potential conflicts of interest

The authors report no conflict of interest. No financial interest or benefit has arisen from the direct application of our research. S.M.K. and N.M. are used by the Pure North S'Energy Foundation.

Acknowledgments

The authors would like to thank Mr. Ken Fyie for his work in constructing the data set and Dr. Paul Veugelers for his comments on the manuscript.

Funding

There was no funding provided directly for this work. Salaried employees of Pure North S'Energy Foundation, a not for profit organization, designed the study, performed data analyses and wrote the manuscript in collaboration with Dr. Michael F. Holick from Boston University Medical Center, who participated in the analysis and writing of the manuscript.