Walsh, J.S. orcid.org/0000-0002-7122-2650, Evans, A.L., Bowles, S. et al. (5 more authors) (2016) Free 25-hydroxyvitamin D is low in obesity, but there are no adverse associations with bone health. American Journal of Clinical Nutrition. ISSN 0002-9165
Abstract
Background: The mechanism and clinical significance of low circulating 25-hydroxyvitamin D [25(OH)D] in obese people are unknown. Low total 25(OH)D may be due to low vitamin D–binding proteins (DBPs) or faster metabolic clearance. However, obese people have a higher bone mineral density (BMD), which suggests that low 25(OH)D may not be associated with adverse consequences for bone.
Objective: We sought to determine whether 1) vitamin D metabolism and 2) its association with bone health differ by body weight.
Design: We conducted a cross-sectional observational study of 223 normal-weight, overweight, and obese men and women aged 25–75 y in South Yorkshire, United Kingdom, in the fall and spring. A subgroup of 106 subjects was also assessed in the winter. We used novel techniques, including an immunoassay for free 25(OH)D, a stable isotope for the 25(OH)D3 half-life, and high-resolution quantitative tomography, to make a detailed assessment of vitamin D physiology and bone health.
Results: Serum total 25(OH)D was lower in obese and overweight subjects than in normal-weight subjects in the fall and spring (geometric means: 45.0 and 40.8 compared with 58.6 nmol/L, respectively; P < 0.001) but not in the winter. Serum 25(OH)D was inversely correlated with body mass index (BMI) in the fall and spring and in the winter. Free 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)2D] were lower in obese subjects. DBP, the DBP genotype, and the 25(OH)D3 half-life did not differ between BMI groups. Bone turnover was lower, and bone density was higher, in obese people.
Conclusions: Total and free 25(OH)D and 1,25(OH)2D are lower at higher BMI, which cannot be explained by lower DBP or the shorter half-life of 25(OH)D3. We speculate that low 25(OH)D in obesity is due to a greater pool of distribution. Lower 25(OH)D may not reflect at-risk skeletal health in obese people, and BMI should be considered when interpreting serum 25(OH)D as a marker of vitamin D status.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Editors: |
|
Copyright, Publisher and Additional Information: | © 2016 American Society for Nutrition |
Keywords: | bone density; bone turnover; half-life; obesity; vitamin D; vitamin D–binding protein |
Dates: |
|
Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > Department of Human Metabolism (Sheffield) The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > School of Health and Related Research (Sheffield) > ScHARR - Sheffield Centre for Health and Related Research The University of Sheffield > Sheffield Teaching Hospitals |
Funding Information: | Funder Grant number DEPARTMENT OF HEALTH 024/0052 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 16 Aug 2016 12:33 |
Last Modified: | 16 Aug 2016 12:33 |
Published Version: | http://dx.doi.org/10.3945/ajcn.115.120139 |
Status: | Published |
Publisher: | American Society for Nutrition |
Refereed: | Yes |
Identification Number: | 10.3945/ajcn.115.120139 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:98488 |