Why is vitamin D often deficient or less bioavailable in obese individuals?

• A. It is rapidly excreted in urine
• B. It is produced in adipose tissue
• C. It is not absorbed in the intestine
• D. Its bioavailability is lower and it is sequestered in adipose tissue

Answer: (D)

Vitamin D is a fat-soluble vitamin, so it dissolves in and is stored within adipose tissue. In individuals with greater fat mass, more vitamin D gets sequestered in fat stores, which reduces the amount circulating in the bloodstream that can be available for conversion to its circulating and active forms. This sequestration and the resulting dilution in the larger body pool lower the bioavailability of vitamin D, contributing to deficiency despite similar intake or sun exposure. The other statements don’t fit because vitamin D isn’t rapidly excreted in urine, isn’t produced in adipose tissue, and its intestinal absorption isn’t inherently impaired simply due to obesity.