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Related Experiment Video

Updated: Jul 7, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

Published on: December 9, 2015

Vitamin D toxicity, policy, and science.

Reinhold Vieth¹

¹Departments of Nutritional Sciences, and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.

Journal of Bone and Mineral Research : the Official Journal of the American Society for Bone and Mineral Research

|March 20, 2008

Summary

Vitamin D toxicity levels remain unclear, but current evidence suggests 10,000 IU daily is safe for most adults. Higher intake may be needed for those with limited sun exposure to maintain adequate vitamin D levels.

Related Experiment Videos

Last Updated: Jul 7, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

Published on: December 9, 2015

Area of Science:

Nutritional Biochemistry
Endocrinology
Public Health

Background:

The established tolerable upper intake level (UL) for vitamin D is 50 µg (2000 IU)/day.
Vitamin D toxicity threshold and hypercalcemia risk factors require further clarification.
Sun exposure can provide vitamin D equivalent to 10,000 IU/day, suggesting higher oral intakes may be safe.

Purpose of the Study:

To evaluate the safety and potential upper intake levels of vitamin D.
To determine if current tolerable upper intake levels are adequate for maintaining sufficient serum 25-hydroxyvitamin D concentrations.
To investigate the mechanisms limiting vitamin D safety.

Main Methods:

Review of clinical trial evidence on vitamin D intake and serum concentrations.
Analysis of physiological mechanisms regulating vitamin D metabolism and toxicity.
Comparison of vitamin D intake from sun exposure versus oral supplementation.

Main Results:

A prolonged intake of 250 µg (10,000 IU)/day of vitamin D3 is likely safe for most individuals.
Serum 25(OH)D concentrations above 600 nM (240 ng/ml) may lead to excessive free 1,25-dihydroxyvitamin D and hypercalcemia.
The body has mechanisms, including vitamin D-binding protein capacity, that limit vitamin D toxicity.

Conclusions:

The tolerable upper intake level for vitamin D may need re-evaluation.
Daily intake of 10,000 IU of vitamin D3 appears safe and may be necessary for some populations.
Understanding vitamin D metabolism is crucial for establishing safe and effective intake recommendations.