Vitamin D is also known as the sunshine vitamin, and belongs to the group of fat-soluble vitamins. It is also considered as a prohormone, or a precursor to hormones, and is the only vitamin that can be naturally synthesized by human skin on exposure to the ultraviolet radiation of sunlight. It is mainly required by our body to maintain the normal level of calcium and phosphorus in the blood. It is available in two main forms, ergocalciferol or vitamin D2, and cholecalciferol or vitamin D3. Just as a vitamin D deficiency can cause health problems, excess of this vitamin too can lead to some serious complications.
Vitamin D Toxicity
Most people taking vitamin D supplements are unaware of the fact that, if present in higher than the required amounts, this vitamin can be toxic. This is known as vitamin D toxicity, which can result either from a single overdose of supplementation or intake of small doses for a prolonged time period. Higher levels of this vitamin in the body can give rise to some really serious consequences or side effects.
When the level of vitamin D increases in the body, it raises the level of calcium in the blood. The obvious result of this condition is hypercalcemia (presence of abnormally high level of calcium in blood), and is responsible for producing most of the symptoms. The early symptoms include:
- Bone pain
- Constant headache
- Irregular heartbeat
- Loss of appetite
- Muscle and joint pain
- Frequent urination
- Excessive thirst
Probable Toxic Levels
A deficiency of vitamin D can impair the normal absorption of calcium and phosphorus, and is known to cause rickets in children, and osteomalacia and osteoporosis in adults. A deficiency of vitamin D can either result from inadequate exposure to sunlight or insufficient dietary intake. Sometimes, even if it is absorbed, the body cannot convert it into an active form, mainly in conditions like liver, kidney, and hereditary diseases. In addition to these, older individuals are more likely to suffer from vitamin D deficiency, as the ability of the skin to produce this vitamin declines with advancing age. Therefore, many individuals have to take supplementation of vitamin D, to meet the daily requirement.
The most common contributory factor for vitamin D toxicity is overdosing on vitamin D supplements. It is therefore essential to take it as per the prescribed dosage. Regular dietary allowance (RDA) of vitamin D for a normal person is around 600 international units (IU) per day. However, dosage higher than this recommended level is usually prescribed for a person suffering from vitamin D deficiency. The exact toxic level of this vitamin has yet to be determined, nevertheless, consumption of 40,000 - 50,000 IU per day, for several months is most likely to cause vitamin D toxicity.
Though our skin can synthesize vitamin D in the presence of sunlight, prolonged exposure to sunlight cannot cause toxicity. Toxicity is also less likely to be produced by the intake of vitamin D rich foods, like salmon, mackerel, tuna, sardines, soy products, seaweeds, legumes, beans or milk and dairy products fortified with this vitamin.
Adequate precautionary measures should be followed while taking any supplementation. Individuals taking vitamin D supplements should consult a physician regarding its appropriate or safe doses, and remain vigilant for the symptoms of its toxicity.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be used as a replacement for expert medical advice.