How Obesity Affects Vitamin D Metabolism

21/02/2019 Wiley
A newJournal of Bone and Mineral Researchstudy confirms that vitamin D supplementation is less effective in the presence of obesity, and it uncovers a biological mechanism to explain this observation.

The study reveals that obese mice have very low levels of the enzyme in the liver that converts vitamin D into 25-hydroxyvitamin D (calcidiol), which is the major form of vitamin D in the blood. Therefore, it may be more effective to treat vitamin D insufficiency in obese individuals with calcidiol rather than with other forms of vitamin D.

“Low circulating levels of 25-hydroxyvitamin D are common in obesity and have been attributed to sequestration of vitamin D in fat cells. Here we propose a second mechanism with greater biological implications: obesity reduces the ability of the liver to convert vitamin D into 25-hydroxyvitamin D,” said lead author Dr. Jeffrey Roizen, of The Children’s Hospital of Philadelphia. “Our observations show that this early step in activating vitamin D is influenced by obesity, and suggest that obesity-related effects on the liver can have clinically important systemic effects on bone and mineral metabolism. Further, while we often think of low vitamin D causing obesity, this work shows that an illness or pathology (like obesity) can cause low vitamin D.”

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Roizen, J. D., Long, C. , Casella, A. , O'Lear, L. , Caplan, I. , Lai, M. , Sasson, I. , Singh, R. , Makowski, A. J., Simmons, R. and Levine, M. A. (2019), Obesity Decreases Hepatic 25‐Hydroxylase Activity Causing Low Serum 25‐Hydroxyvitamin D. JBMR. DOI:10.1002/jbmr.3686

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