Vitamin D is not found in many foods, but it's available as a dietary supplement. Vitamin D is synthesized in your body when your skin is exposed to the ultraviolet rays of the sun. You won't get toxic levels of vitamin D from sunlight, but health risks have been associated with taking large amounts of vitamin D supplements.
Vitamin D Functions
Vitamin D helps your body absorb calcium, so it's important for strong bones and teeth. It's also necessary for immune system function, acts as an anti-inflammatory agent, and signals cell growth. Vitamin D deficiency can result in bone-softening diseases called rickets in children and osteomalacia in adults. Osteomalacia can lead to osteoporosis.
Recommended Amounts
The Food and Nutrition Board of the Institute of Medicine determines Dietary Reference Intakes, or DRI, for vitamin D based on minimal sun exposure. You need 600 IU of vitamin D from age 1 to 70, and 800 IU after the age of 70. The Food and Nutrition Board sets 4,000 IU as the upper tolerable limit for vitamin D intake for anyone age 9 or older, although the Office of Dietary Supplements of the National Institutes of Health says lower amounts taken over prolonged periods of time might have adverse health affects.
Vitamin D Supplements
Vitamin D supplements are available in two forms: vitamin D3, or cholecalciferol, and vitamin D2, or ergocalciferol. However, most vitamin D supplements contain D3, and most research suggests the body processes vitamin D3 more easily. Small amounts are included in multiple vitamins, and it is usually found with calcium supplements or sold as a solitary vitamin. Vitamin D is fat-soluble, meaning your body can store it in your fat tissues, so you shouldn't take large amounts of vitamin D. Always speak to your doctor before taking vitamin D supplements for any reason.
Excess Vitamin D
Vitamin D from supplements can build up enough to become toxic. Hypervitaminosis D can cause nausea, vomiting, poor appetite, constipation, weakness, confusion, heart rhythm problems and kidney stones, according to the Mayo Clinic. The Office of Dietary Supplements of the National Institutes of Health says calcium and vitamin D supplements with 400 IU of vitamin D have been associated with a risk of kidney stones in post-menopausal women.
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