Vitamin D
Although vitamin D is essential for your health, a vitamin D overdose can threaten your health. It causes Hypervitaminosis D, a potentially serious condition that results from toxic levels of this vitamin in the body.
Causes of Vitamin D Overdose
The body's daily requirement for vitamin D is relatively low. It naturally produces its daily supply from exposure to sunlight, the primary source of vitamin D. As little as 10 to 15 minutes of sunshine, at least three times a week, is enough to manufacture your body's vitamin D requirement.
This natural production process is safe and will not result in an overdose, because once the body's requirements have been met, further production of this vitamin is shutdown. High dietary intakes of vitamin D from food sources have also been proven to contain concentrations of vitamin D that are too low to cause an overdose (with the exception of cod liver oil).
The most likely cause of vitamin D overdose is from an excessive intake of supplements. The body does not have a mechanism to shutdown the absorption of large amounts of vitamin D from supplemental vitamin preparations. As such, it builds up to toxic levels, causing Hypervitaminosis D. Such incidents are most closely associated with prescription supplements of vitamin D.
People most vulnerable to an overdose are often those who suffer from rickets or some other disease or condition that is caused by vitamin D deficiency. In this case, pharmacological doses are prescribed for therapeutic purposes.
How Much is Too Much?
Vitamin D overdose typically happens over a period of time rather than from a single large dose. This is because, unlike most other essential nutrients we consume, the body does not excrete excess vitamin D. Instead, it is stored in the body's fat cells where it can accumulate to toxic levels over time.
According to the National Institutes of Health, the Upper Intake Levels (ULs) for the vitamin D are as follows:
Birth to 12 months of age: 25 micrograms (1,000 IU)
One year of age or older: 50 micrograms (2,000 IU)
Studies have also shown that, taken over long periods of time, consumption of vitamin D in amounts above the UL will result in toxicity. For children under the age of 12 months, a sustained intake of 1,000 micrograms (40,000 IU) a day will produce toxicity in just one to four months. For adults, 2,500 micrograms (100,000 IU) a day may result in toxicity in a few months.
Health Risks of Overdosing on Vitamin D
Some of the health risks of excessive intake of vitamin D include:
Elevated levels of calcium in the blood, resulting from an increase in the absorption of calcium in the intestinal tract
Abnormally large deposition of amounts of phosphate and calcium in soft tissue such as the lungs, heart and kidneys. These deposits can cause irreversible organ malfunction.
Nausea, vomiting, poor appetite and loss of weight
High blood pressure, heart rhythm irregularities and increased risk of heart disease
Kidney stones and renal failure
Excessive production of urine
An overdose of Vitamin D in pregnant women can cause mental or physical retardation in babies.
Other symptoms include:
Bone pain and even bone loss
Muscular weakness and fatigue
Nervousness and irritability
Excessive thirst, dehydration
Severe headache
Deafness
Itchy skin
http://www.vitamindcouncil.org/newsletter/vitamin-d-and-h1n1-swine-flu.shtml