Vitamin D is known as the "sunshine vitamin" because your body manufactures it when exposed to sunlight. Vitamin D occurs naturally in relatively few dietary sources, such as fatty fish and fortified food. A vitamin D supplement may be helpful if your diet is vitamin D deficient and you don't spend much time in the sun. However, taking too much vitamin D-3 can cause hypervitaminosis D, also known as vitamin D toxicity. (Ref 6)
Function and Use
Vitamin D is a fat-soluble vitamin best known for its bone health benefits; it helps your body absorb and use the mineral, calcium. Vitamin D also encourages a healthy immune system and may reduce your risk for cancer. Vitamin D deficiency in adults results in osteomalacia, a condition in which the bones soften. Elderly people whose diets are deficient in this nutrient and people who don't get a lot of sunlight are at risk for osteomalacia, as are people with certain chronic medical conditions. Vitamin D supplements are used to treat osteomalacia and other conditions such as hyperparathyroidism, psoriasis and rickets in children. Vitamin D-2 and vitamin D-3 are the two forms of vitamin D. These go by the names "ergocalciferol" and "cholecalciferol." Vitamin D-3, or cholecalciferol, is found in most over-the-counter dietary supplements. According to the University of Maryland Medical Center, it would be difficult to get too much vitamin D from food, and it's impossible to get too much of this nutrient from sun exposure. When hypervitaminosis D occurs, it's almost always caused by excessive amounts of supplemental vitamin D.
Toxicity
Too much vitamin D-3 can make you sick when taken in toxic amounts, resulting in a condition called hypercalcemia, or abnormally high blood calcium levels. In its early stages, symptoms of hypercalcemia include nausea, vomiting, anorexia, excess thirst and urination, headache, tiredness, sleepiness, dry mouth, a metallic taste in the mouth, dizziness, an unsteady gait and ringing in the ears. Prolonged hypercalcemia can cause kidney stones, bone loss and calcification of vital organs such as the heart and kidneys. People with kidney or liver problems and those who take certain types of diuretics may be more susceptible to hypervitaminosis D, states MayoClinic.com writer and nutritionist Katherine Zeratsky.
Safety
According to the Linus Pauling Institute, vitamin D toxicity generally occurs at dosages of more than 50,000 IU a day, and it's rarely seen in healthy individuals who get less than 10,000 IU a day. The tolerable upper intake level, or UL, established for healthy adults and children ages 9 and older is 4,000 IU a day, or 100 mcg.
Other Information
Vitamin D toxicity is first treated by supplement cessation. According to the Merck Manual for Health Care Professionals, rehydration therapy may be necessary using intravenous liquids consisting of saline and other medications to reduce blood calcium levels. Calcification of the vital organs may be irreversible, however. The Dietary Guidelines for Americans 2010 advises you to get your essential nutrients from the foods you eat rather than supplements. Please talk to your health care provider before taking supplemental vitamin D-3 to address your health and nutrition concerns.
References
- Linus Pauling Institute at Oregon State University: Vitamin D; J. Higdon, Ph.D.; March 2004
- University of Maryland Medical Center: Vitamin D; June 2010
- The Merck Manual for Health Care Professionals: Vitamin D; L. Johnson, M.D.; April 2007
- MayoClinic.com; Vitamin D Toxicity: What if You Get Too Much?; K. Zeratsky; December 2010
- MayoClinic.com: Vitamin D; July 2011
- U.S. Office of Dietary Supplements: Vitamin D;
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