What Can Cause Vitamin D Deficiency?

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Avoiding direct sunlight and eating a diet containing insufficient amounts of vitamin D can lead to vitamin D deficiency, according to WebMD. Illnesses that damage the ability of the intestine to absorb vitamin D, such as celiac disease, cystic fibrosis and Crohn's disease, can also lead to vitamin D deficiency. Because fat cells extract vitamin D from the blood, people who are obese often have a vitamin D deficiency.