Vitamin D is a fat-soluble vitamin responsible for the absorption of calcium and bone mineralization. Cholecalciferol, also known as vitamin D3, is the form of vitamin D that your body produces after exposure to sunlight. Once absorbed, vitamin D3 undergoes a series of chemical reactions in the liver to become the calcidiol. In the kidneys, it is then converted into the biologically active calcitriol. Although vitamin D is essential for good health, too much vitamin D3 in the body has potentially serious health risks.
The Sunshine Vitamin
Vitamin D is unique in that your body can produce it under special circumstances. Just 10 minutes in the bright sun can give your body the vitamin D boost it needs. Sun exposure is an easy and reliable way for most people to get vitamin D. Adequate levels of vitamin D3 promotes overall health and a sense of well-being. Nevertheless, vitamin D deficiency is common among the elderly and individuals living in Canada and the northern United States who do not received adequate sun exposure, especially during the winter months. Vitamin D3 supplements are available for these individuals.
Recommended Dietary Allowance
The Food and Nutrition Board at the Institute of Medicine established the average daily level of vitamin D sufficient to maintain bone health and normal calcium metabolism in healthy people. Men and women through the age of 70 require 600 IU of vitamin D per day. As the elderly are more likely to be deficient in vitamin D, their needs are higher. They require 800 IU per day.
Tolerable Upper Intake
At high levels vitamin D can cause adverse reactions. For this reason, the Food and Nutrition Board at the Institute of Medicine established tolerable upper intake levels. This is the maximum daily intake unlikely to cause unwarranted effects. For all adults, this level is 4,000 IU per day. Therefore, getting more than 4,000 IU of vitamin D3, either from dietary sources, supplements or sun exposure, poses potential health risks.
Toxicity
A high level of vitamin D3 can cause a toxicity, also known as hypervitaminosis D. Excessive vitamin D causes abnormally high levels of calcium in the blood, which can severely damage the bones, soft tissues and kidneys. Hypervitaminosis D also causes non-specific symptoms such as vomiting, constipation, loss of appetite, anorexia, dehydration, fatigue, irritability, polyuria, muscle wasting and heart arrhythmias. Excessive sun exposure does not result in hypervitaminosis D as the body is able to absorb only what it needs. Vitamin D toxicity is not typically the result of dietary consumption, but rather over supplementation.
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