How Much Vitamin D is Toxic?

Do we need to worry about Vitamin D toxicity? Not according to this Q&A I just read unless you are one of a very small subset of people who have hypersensitivity to Vitamin D and related conditions (listed below).  Makes interesting reading and some of the response comes from one of the leading Vitamin D researchers in the world, so thought you might like it…

Q: Is vitamin D toxic?

A: Not if we take the same amount nature intended when we go out in the sun. Vieth demonstrated that we make about 10,000iu when we go out in the sun uncovered for 20 minutes.

In 1999, Vieth indirectly asked the medical community to produce any evidence 10,000 units of vitamin D a day was toxic, saying “Throughout my preparation of this review, I was amazed at the lack of evidence supporting statements about the toxicity of moderate doses of vitamin D.” He added: “If there is published evidence of toxicity in adults from an intake of 250 ug (10,000 IU) per
day, and that is verified by the 25(OH)D concentration, I have yet to find it.”

All ingested items have a dose related toxicity risk. This is a well understood correlation in medicine. The human intake of vitamin D3 required to achieve the equivalent toxic level to kill rats equates to a 110-pound adult taking 176,000,000 IU or 440,000 of the 400 unit cholecalciferol (D3) drops at once.

Reinhold Vieth is recognised as one of the leading researchers in the world on Vitamin D and reports human toxicity probably begins to occur after chronic daily consumption (over several years) of approximately 40,000 IU/day (100 of the 400 IU drops per day).

Heavy sun exposure when combined with excessive supplement use is a theoretical risk for vitamin D toxicity, but if such a case has been reported, I am not aware of it.

It is true that a few people may have problems with high calcium due to undiagnosed vitamin D hypersensitivity syndromes such as primary hyperparathyroidism, granulomatous disease, or occult cancers, but a blood calcium level, PTH, 25(OH)D, and calcitriol level should help clarify the cause of the hypersensitivity.

Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentration, and safety. Am J Clin Nutr. 1999;69:842–56. View Full Paper

To ensure optimal Vitamin D, the advice is:

Take 5,000iu per day for three months, then obtain a 25-hydroxyvitamin D test. Adjust your dosage so that blood levels are between 50–80 ng/mL (or 125–200 nM/L) year-round.

Yep, that’s been my advice too for the last few years.

Source: NutriLink Clinical Education Mucosal Immune Support

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