Maintaining sufficient levels of vitamin D, or calcitriol -- a hormone with a molecular structure similar to cholesterol -- helps to maintain your health. Your total vitamin D intake comes from vitamin supplements, vitamins in the foods you eat, and the vitamin D synthesized within the pigment cells of your skin upon exposure to sunlight. However, like most things in life, your vitamin D levels are best kept in moderation, and abnormally high or low levels of the vitamin can prove harmful. Taking vitamin D mega-dosages -- doses sometimes several times your recommended intake -- can negatively affect your health.
Upper Tolerable Limit
Vitamin D mega-dosages may exceed the recommended upper intake levels for vitamin D. Excess levels of calcitriol are stored in your liver and are not excreted from your body, so you should not exceed your upper tolerable limit to avoid vitamin overdose. The Linus Pauling Institute recommends that adults not exceed 100 mcg, or 4000 IU, of vitamin D daily. Consuming mega-doses of vitamin D larger than the upper tolerable limit can potentially lead to a number of side effects.
Danger to Bones
One of the main dangers of vitamin D mega-doses comes from its regulation of bone tissue. Vitamin D helps to control how calcium is localized within your body. Since almost all of of your body's calcium is in your bone tissue, vitamin D mega-dosages affect your bones. A vitamin D mega-dosage signals for calcium to leave your bones and enter your bloodstream, leading to a loss of mineralized bone tissue and a risk of bone damage.
Effects on Other Tissues
Vitamin D megadoses increase your blood calcium level, which can affect a number of other tissues. The high level of calcium in your blood can eventually lead to calcium deposits in other tissues, including your blood vessels and kidneys. The defects in calcium localization can also affect your nervous and muscular systems, leading to muscle weakness. Finally, vitamin D megadoses can lead to fatigue and digestive issues like vomiting and constipation.
Preventing Vitamin D Toxicity
You can prevent the side effects associated with vitamin D megadoses by consuming moderate amounts of the vitamin, only as instructed by a physician. In many cases, you can produce adequate vitamin D through normal sun exposure. If you already suffer from vitamin D deficiency, or live in a region with little sunlight, talk to your doctor to determine an appropriate vitamin dosage to meet your body's needs without causing a vitamin overdose.
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