A growing body of research links vitamin D deficiency to a number of disorders. Studies suggest that a greater percentage of the population than once thought might be deficient in this important nutrient. More and more health care providers are testing their patients for vitamin D deficiency. When supplementation is recommended to address a deficiency, proper dosing and duration strategies are vital.
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Breastfed infants, older adults, people with limited sun exposure, dark-skinned people, those with fat malabsorption disorders or those who have undergone gastric bypass surgery are at increased risk for developing a deficiency of vitamin D, according to the Office of Dietary Supplements, a division of the National Institutes of Health. While it might be appropriate for people in these risk groups to take a vitamin D supplement, therapeutic doses containing very high levels of vitamin D should only be taken by those with confirmed deficiencies. A blood test performed by your health care provider is necessary to detect a vitamin D deficiency.
The needs and tolerances for vitamin D vary with age. The Linus Pauling Institute at Oregon State University lists the Recommended Daily Allowances, or RDA, at 400 International Units, or IU, for infants; 600 IU for those ages 1 to 70 years old; and 800 IU for those over 70. Tolerable upper-intake levels range from 1,000 IU for infants to 4,000 IU for adults. The Linus Pauling Institute suggests 2,000 IU per day as a therapeutic dose for most adults. Higher oral doses or even injected doses might be recommended in some cases under physician supervision.
While some experts contend that a reasonable therapeutic dose of vitamin D can be maintained indefinitely, others argue that therapeutic doses should be reduced to RDA levels once the deficiency has been corrected. The most reliable way to determine when the deficiency has been resolved is to have your blood levels re-assessed. Guidelines established by the Pharmacy Department at the University of Maryland recommend testing blood levels of vitamin D every eight weeks until normal levels are established. Annual testing is recommended after that to ensure that adequate levels are maintained.
Though the risks of deficiency are greater than the risks of toxicity, in the case of vitamin D, it is possible to get too much of a good thing. According to the Vitamin D Council, a specific toxic dose of vitamin D has not been determined, probably because tolerance levels vary widely between individuals. The council warns that symptoms such as nausea, vomiting, poor appetite, constipation, weakness, weight loss, tingling sensations in the mouth, confusion and heart rhythm abnormalities can surface from vitamin D toxicity. If these symptoms develop while you are supplementing vitamin D, you should stop taking the supplements and consult your health care provider.