Definition

Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body's liver and fatty tissues. Vitamin D acts as both a vitamin and a hormone. Two of the main sources of vitamin D are food and sunlight. The ultraviolet rays of the sun react with cholesterol present on the skin and create previtamin D3. This compound goes through a series of reactions involving the kidneys and the liver. The final product is vitamin D.

Vitamin D deficiency describes low levels of vitamin D in the blood. This condition can lead to a condition known as rickets in children. In adults, it can lead to osteomalacia . These are two forms of bone diseases that weaken bones. It is important to contact your doctor if you think you have vitamin D deficiency.

Weakened Bone

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Causes

Vitamin D deficiency can be caused by:

• Inadequate intake of vitamin D in the diet
• Lack of sunlight due to:
  • Having a darker skin color
  • Wearing clothes that cover most of the skin
  • Living in northern latitudes during the winter
  • Not being exposed to direct sunlight—Sunlight through windows, clothes, or sunscreen-covered skin is not enough for the body to synthesize vitamin D.
• Conditions and procedures that affect the body’s ability to absorb vitamin D from the digestive tract (eg, celiac disease , inflammatory bowel disease , bariatric surgery)
• Conditions or medicines that affect the process of converting vitamin D to a form that the body can use, such as:
  • Anti-seizure medicines such (eg, phenobarbital , phenytoin , carbamazepine )
  • Other medicines (eg, rifampin , isoniazid , theophylline )
  • Severe liver disease
  • Chronic kidney disease
  • Vitamin-D dependant rickets (an inherited condition)
  • Hypoparathyroidsim (underactive parathyroid)
  • Nephrotic syndrome (kidney condition)
  • Peritoneal dialysis

Risk Factors

Risk factors include:

• Limited sun exposure
• Darker skin color
• Kidney disease
• Restricted activity (eg, due to hospitalization)
• Injury due to a severe burn
• Malabsorption disorder (eg, celiac disease)
• Obesity
• Certain types of diets (eg, macrobiotic diet)
• Liver conditions
• Babies who are breastfed or do not consume enough formula that is fortified with vitamin D

Wearing sunscreen may be a risk factor for vitamin D deficiency. But, organizations like the American Academy of Dermatology (AAD) recommend that you use sunscreen to protect your skin from UV exposure, a known risk factor for skin cancer.

Symptoms

If your vitamin D deficiency is mild to moderate, you may not have any symptoms. If you have a severe deficiency, you may experience:

• Bone and muscle pain
• Muscle weakness
• Hip pain
• Fractures
• Difficulty walking, walking up stairs, and getting out of a chair
• Falls

Diagnosis

Treatment

Talk with your doctor about the best plan for you. Treatment options include:

• Vitamin D supplementation—High doses of vitamin D are given for 6-12 weeks. This is followed by a lower dose of the vitamin. The doses are continued until blood levels return to normal.
• Calcium supplementation—Calcium plus vitamin D supplements may be given to increase D levels. This can also improve bone strength in older women with low vitamin D.
• Light therapy—Exposure to sunlight or UV radiation can increase D levels. Vitamin D3 is produced in the skin when it is exposed to these light sources.

Prevention

To prevent vitamin D deficiency, take these steps:

• Eat a healthy diet. Foods are not naturally high in vitamin D. Many foods are enriched with vitamin D, such as milk, juices, and cereal.
• Take a vitamin D supplement if recommended by your doctor. Your baby may need a supplement if he is breastfed or does not consume enough formula that is fortified with vitamin D. Children may also need to take a supplement if they are not getting enough vitamin D in their diets.
• Follow your doctor’s guidelines on getting enough sun exposure.
• If you or a family member has any of the above risk factors, talk to the doctor about other ways to avoid becoming deficient in vitamin D.