Vitamin D is a fat-soluble vitamin your skin can make from the sun, but is naturally present in few foods. Vitamin supplements are the main source of vitamin D for many people. While sufficient vitamin D is important for good health, too much can be harmful. You cannot get too much vitamin D from the sun, and it would be difficult to get too much from food. However, it is possible to get more than your body can tolerate from supplements.
Function
Vitamin D works with calcium to build and maintain strong bones. Without vitamin D, bones can become thin, brittle and misshapen, leading to rickets in children and osteoporosis in older adults. The Office of Dietary Supplements, indicates that vitamin D has other functions, including helping immune function, reducing inflammation and controlling cell growth. The body stores vitamin D in fat and does not excrete excessive amounts as it does with some other vitamins, such as vitamin C. Because of this storage, it is possible to get too much vitamin D.
Tolerable Levels
To build strong bones and help maintain good health, 600 International Units of vitamin D are recommended for adults 70 and younger. Seniors over 70 should get 800 IU. The ODS lists tolerable levels as 4,000 IU for all adults.If you get more than 4,000 IU of vitamin D per day, you could develop vitamin D toxicity, a potentially serious medical condition. Vitamin D toxicity usually results from consuming excessive amounts of vitamin D in supplements, but vitamin D toxicity is rare even in people who take supplements, MayoClinic.com notes.
Overdose Effects
Vitamin D toxicity causes a buildup of calcium in the blood. Signs of vitamin D toxicity include nausea, vomiting, poor appetite, constipation, weakness, confusion, abnormal heart rhythms and kidney stones. Treatment may include stopping the supplements and restricting calcium intake, as well as medicine. In severe cases, hospitalization may be necessary. Sometimes doctors recommend high doses of vitamin D to for a short time to treat a medical condition, such as vitamin D deficiency, but these doses should be given under the care of a doctor.
Drug Interactions
Vitamin D supplements can interact with a number of medications. The weight loss drug orlistat, which is sold under the brand names Alli and Xenical, and certain cholesterol-lowering drugs can reduce the absorption of vitamin D, reports the ODS. Corticosteroid medications such as prednisone can reduce calcium absorption and impair vitamin D metabolism, increasing the risk of osteoporosis. To prevent vitamin D toxicity or drug interactions, discuss taking supplements with your doctor.
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