Vitamin D Deficiency and Overdose

Vitamin D Deficiency

Vitamin D Deficiency can have dramatic consequences on your health. Nutrient deficiencies are usually the result of dietary inadequacy, impaired absorption and use, increased requirement, or increased excretion. A vitamin D deficiency can occur when usual intake is lower than recommended levels over time, exposure to sunlight is limited, the kidneys cannot convert vitamin D to its active form, or absorption of vitamin D from the digestive tract is inadequate. Vitamin D-deficient diets are associated with milk allergy, lactose intolerance, and strict vegetarianism.

Rickets and osteomalacia are the classical vitamin D deficiency diseases. In adults, vitamin D deficiency can lead to osteomalacia, resulting in weak muscles and bones. Symptoms of bone pain and muscle weakness can indicate inadequate vitamin D levels, but such symptoms can be subtle and go undetected in the initial stages.

Groups at Risk of Vitamin D Inadequacy
Obtaining sufficient vitamin D from natural food sources alone can be difficult. For many people, consuming vitamin D-fortified foods and being exposed to sunlight are essential for maintaining a healthy vitamin D status. In some groups, dietary supplements might be required to meet the daily need for vitamin D. As a fat-soluble vitamin, vitamin D requires some dietary fat in the gut for absorption. Individuals who have a reduced ability to absorb dietary fat might require vitamin D supplements Fat malabsorption is associated with a variety of medical conditions including pancreatic enzyme deficiency, Crohn's disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease People who are obese are also at risk as vitamin D is sequestered in the body fat.

Osteoporosis
More than 25 million adults in the United States have or are at risk of developing osteoporosis, a disease characterized by fragile bones that significantly increases the risk of bone fractures Osteoporosis is most often associated with inadequate calcium intakes (generally <1,000-1,200 mg/day), but insufficient vitamin D contributes to osteoporosis by reducing calcium absorption Although rickets and osteomalacia are extreme examples of the effects of vitamin D deficiency, osteoporosis is an example of a long-term effect of calcium and vitamin D insufficiency. Adequate storage levels of vitamin D maintain bone strength and might help prevent osteoporosis in older adults, nonambulatory individuals who have difficulty exercising, postmenopausal women, and individuals on chronic steroid therapy.

During menopause, the balance between these processes changes, resulting in more bone being resorbed than rebuilt. Hormone therapy with estrogen and progesterone might be able to delay the onset of osteoporosis. The decreased risk of fractures occurred primarily in elderly women aged 85 years, on average, and living in a nursing home. Women should consult their healthcare providers about their needs for vitamin D (and calcium) as part of an overall plan to prevent or treat osteoporosis.

Vitamin D Overdose

Excessive sun exposure does not result in vitamin D toxicity because the sustained heat on the skin is thought to photodegrade previtamin D3 and vitamin D3 as it is formed High intakes of dietary vitamin D are very unlikely to result in toxicity unless large amounts of cod liver oil are consumed; toxicity is more likely to occur from high intakes of supplements.

Interactions with Medications
Vitamin D supplements have the potential to interact with several types of medications. Corticosteroid medications such as prednisone, often prescribed to reduce inflammation, can reduce calcium absorption and impair vitamin D metabolism. These effects can further contribute to the loss of bone and the development of osteoporosis associated with their long-term use. Interaction with other medications can also reduce vitimin D absorption and this should be discussed with a medical professional.

Certain Supplements cannot cause harm as quantities in excess of need is excreted from the body. Other supplements, including Vitamin D, should not be taken without the advise of your medical professional as they stay in the body and can cause symptoms.

(This information was compiled from the Dietary Supplement Fact Sheet on Vitamin D provided by the Office of Dietary Supplements of the National Institutes of Health (USA) - website: http://ods.od.nih.gov )

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