Vitamin D Deficiency

What causes a vitamin D deficiency? (Continued)


Research has begun to show a relationship between BMI and vitamin D deficiency. A study done on 2,187 overweight and obese subjects found that those with a BMI above 40 had 18% lower serum vitamin D levels than those with a BMI under 40. Another study done compared the vitamin D levels of 154 obese subjects to those of 148 nonobese subjects and found that the obese subjects' vitamin D levels were 23% lower. Some possible reasons for this are lower intakes of vitamin D, less exposure to sunlight (UV radiation), and a higher distribution volume of vitamin D. Even with exposure to sunlight, there remains a risk for a deficiency. One study tested the blood levels of vitamin D after sun exposure in both obese and nonobese subjects. It found that there was 57% less vitamin D in the blood of the obese subjects. The exact cause is not known. This emphasizes the importance of having your levels checked regardless of your sun exposure or dietary intake.


People with one of the fat malabsorption syndromes (for example, Crohn's disease, celiac disease) and people who have had bariatric surgery are often unable to absorb enough of the fat-soluble vitamin D.


It has been shown that as we age our body has a decreased ability to synthesize vitamin D from exposure to the sun.

Medications and medical conditions

A wide variety of medications, including antifungal medications, anticonvulsants, glucocorticoids, and medications to treat AIDS/HIV can enhance the breakdown of vitamin D and lead to low levels. There is also a loss of vitamin D for those with chronic kidney disease, primary hyperparathyroidism, chronic granuloma-forming disorders, and some lymphomas.

Reviewed on 7/14/2014
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