Vitamin D - Excess/Toxicity
Excess
Vitamin D appears to have a large buffer between what is excess and what is toxic. When exposed to long periods of sunlight, the body appears to produce 10,000-20,000 IU of vitamin D before it stops.
Toxicity
One expert on vitamin D says that published cases where both the vitamin D blood level indicator (calcifediol) level and vitamin D dosage were known have all been above 40,000 IU. But due to the potential toxicity of vitamin D, intakes exceeding 1,000 IU has been avoided even though the current upper limit of 2,000 IU is substantially low.1
Table 1. Precedent Vitamin D Toxicity and an Estimate of Equivalent Supplementation Requirement
The following table summarizes some of the data forming the basis of vitamin D toxicity levels. Some of the studies referenced in the table involved doctors' prescriptions to treat some disease; others were accidental. The second column was included to demonstrate the difficulty for the average consumer to take toxic doses of vitamin D that would match doses in the studies. 400 IU was used because much of the vitamin D sold over the counter currently comes in tablets containing that amount. Do NOT attempt to reach these levels--or reach anywhere near them--since it would result in an overdose of vitamin D.
| Amount (IU) | Number of 400 IU capsules per day (or specified time period) required to reach this level | Condition/Symptoms |
|---|---|---|
| 40,000/day for 6 months (in a child) | 100 | hypercalcemia (excess blood calcium levels), raised serum calcium2 |
| 50,000/day - 50,000/week for 6 weeks to 5 years | 125 (per day/week, respectively) | hypercalcemia, reduced kidney function3 |
| 50,000/day or higher | 125 | hypercalcemia, loss of urinary concentrating mechanism, polyuria (much urine), polydipsia (excess thirst), decreased renal (kidney) function (i.e. decreased glomerular filtration), increased calcium in the urine, metastatic calcification of soft tissues including the kidney, blood vessels, heart and lungs3 |
| 50,000-200,000 | 125-500 | anorexia, nausea, vomiting3 |
| A range of 35,000-300,000 IU per quart of milk was found in this five year study of a Massachesetts dairy over-fortifying their milk (over that time they found 70-600 times the allowable state limit of 500 IU per quart). Supposing people drink an average between 1 and 3 8-oz glasses, they would have ingested 8750-26250 IU (1 glass) to 75,000-225,000 IU (3 glasses) per day from the over-fortified milk. | 22 to 563 | anorexia, weight loss, weakness, fatigue, disorientation, vomiting, dehydration, polyuria, constipation4 |
| 84,000 IU/day of vitamin D for 5 years | 210 | reduced renal function, nephrolithiasis (kidney stones), and nephrocalcinosis (calcification on functional kidney tissues)3 |
You can see that, at least when it comes to supplementing vitamin D, it would be somewhat difficult for a common consumer to get up to the toxic range, assuming actual vitamin D levels agree with supplement labels, etc. An interesting "commentary" by the health products community on the current 400/600 IU (adult/elderly) Adequate Intake levels is the common availability of vitamin D in the 1000-2000 IU per capsule range.
See Also
Vitamin DVitamin D - How Much?
Vitamin D - Deficiency
References
1. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr, Vol. 69, No. 5, 842-856, May 1999
2. M. W. Moncrieff and G. W. Chance. Nephrotoxic effect of vitamin D therapy in vitamin D refractory rickets. Arch Dis Child. 1969 October; 44(237): 571–579. (http://www.pubmedcentral.nih.gov/pagerender.fcgi?artid=2020083&pageindex=1#page)
3. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine (1997) "Chapter 7: Vitamin D". Dietrary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academy Press. pp. 278-280. ISBN 0-309-06403-1 (pbk.) (http://www.nal.usda.gov/fnic/DRI//DRI_Calcium/250-287.pdf)
4. S Blank, K S Scanlon, T H Sinks, S Lett, and H Falk. An outbreak of hypervitaminosis D associated with the overfortification of milk from a home-delivery dairy. Am J Public Health. 1995 May; 85(5): 656–659. (http://www.pubmedcentral.nih.gov/pagerender.fcgi?artid=1615443&pageindex=1#page)
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