Vitamin D Deficiency Causes

Vitamin D is an important nutrient that helps your body absorb calcium and phosphorus, and may also play a role in immune system function and cell growth. However, despite its importance, many people have low vitamin D levels. In fact, more than 35 percent of Americans may not be getting enough vitamin D, according to the National Center for Health Statistics.

Vitamin D deficiency can have a number of causes, from a lack of sun exposure to a strict vegetarian or vegan diet. In some individuals, certain health conditions can lead to vitamin D deficiency.

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin that plays a critical role in bone growth. It has also been associated with a range of health conditions, from heart disease to colon cancer. Low vitamin D can lead to serious health problems, such as rickets in children and osteomalacia in adults. Vitamin D deficiency symptoms include bone pain, muscle aches and weakness.

Causes of Vitamin D Deficiencies

While vitamin D deficiency is often the result of limited sun exposure, certain health conditions can also contribute to low vitamin D levels. In general, people who have conditions that make it difficult to absorb or process vitamin D are more likely to experience low vitamin D levels.

Conditions that may lead to low vitamin levels include:

  • Celiac disease
  • Certain liver conditions
  • Conditions associated with fat malabsorption (such as cystic fibrois)
  • Conditions associated with irritable bowel syndrome (such as Crohn’s disease)
  • Milk allergy
  • Lactose intolerance
  • Obesity.

Older adults may also have trouble efficiently synthesizing vitamin D. That’s because as you age, your kidneys begin to have difficulty converting vitamin D to its active form. In addition, people who have had gastric bypass surgery may not get adequate vitamin D because part of the upper small intestine, which is important in vitamin D absorption, is affected during surgery.

If you suffer from a condition that makes leaving your home difficult, you may also be at risk of vitamin D deficiency, since your sun exposure is likely to be limited.

Some medications (such as rifampin and certain anticonvulsants) may also interfere with your body’s ability to absorb or process vitamin D.

People who have conditions that lead to low vitamin D may need to take supplements to correct a possible vitamin deficiency. A blood test can determine if you need more vitamin D. If you are thinking about adding vitamin D supplements to your diet, talk to your doctor, since vitamin D can interact with certain medications. In addition, high doses of vitamin D can lead to vitamin D toxicity, particularly in people with kidney problems and certain other conditions.


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National Institutes of Health, Office of Dietary Supplements Staff. (2009). Dietary supplement fact sheet: Vitamin D. Retrieved December 27, 2009, from the National Institutes of Health website: