Vitamin D toxicity seems to be a very common notion today, especially among physicians — apparently, it's a standard theory being taught in medical schools. If you examine it closer, though, it's a theory based on very flimsy evidence and often misinterpreted observations taken from a handful of unusual cases.
What does nature tell us about vitamin D? The most obvious thing to notice about vitamin D is how much nature provides if we just behave naturally as humans, e.g., go out into the sun. Our skin makes at least 10,000 units of vitamin D with just 30 minutes of full body sun exposure. Vitamin D production in the skin starts within minutes and has already "topped off" before your skin turns pink.
Fear of skin cancer is keeping many people out of the sun. The curious thing is that the incidence of melanoma continues to increase although more and more people are avoiding the sun altogether!
I'm not saying long sunbathing sessions are wise — moderation is the key. Full-body sun exposure may slightly increase your risk of skin cancer, but the health risks are certainly much smaller than if you are living with a long-term vitamin D deficiency.
See my page on Vitamin D From Sun Exposure for more details.
Cholecalciferol is the naturally occurring form of vitamin D. It is a prehormone that is synthesized naturally by ultraviolet B irradiation of a cholesterol precursor in your skin.
Cholecalciferol/vitamin D is certainly toxic in excess. However, vitamin D toxicity is virtually unheard of until the dose exceeds 10,000IU per day. In adults, taking 50,000 IU/day for more than a few months can produce toxicity. However, there would be no reason for anyone to do this, except for severe cases of vitamin D deficiency being treated by a health care provider.
Keep in mind that it is not necessarily the dose that determines vitamin D toxicity, but the blood level it generates. If you are being treated by your health care provider for vitamin D deficiency, they should be taking periodic blood samples to monitor your vitamin D levels.
Although vitamin D can be toxic in excess, the same can be said for water! Psychotic patients sometimes sicken themselves by drinking up to 40 glasses a day (known as compulsive water intoxication). There are many other substances that could become toxic if consumed to extreme excess, as well.
See my page on Vitamin D Dosage for more details.
Precautions to use with vitamin D supplementation. If you have any health condition that predisposes you to high calcium in the blood (hypercalcemia), you shouldn't take vitamin D except under the direction of a healthcare provider. These conditions include but are not limited to:
Vitamin D supplements also have the potential to interact with several types of medications. It's always wise to consult with your healthcare provider if you are taking any kind of prescription drug before using vitamin D supplements.
Vitamin D toxicity is also known as hypervitaminosis; it's a condition that occurs after taking excessive amounts of vitamin D. The symptoms of vitamin D toxicity are connected with the consequences of having too much calcium in the blood (hypercalcemia). This occurs once your kidneys’ ability to eliminate calcium is exceeded.
Symptoms of vitamin D toxicity include the following:
Visit other pages in this website on vitamin D:
Other Great Resources for Vitamin D Information
Grassroots Health A consortium committed to solving the worldwide vitamin D deficiency epidemic.
Dr. Mercola Video Lecture on the most up-to-date science on vitamin D.
How Much Vitamin D Do You Need? An article by Dr. Mercola.