Effects of vitamin D supplementation on body fat accumulation, inflammation, and metabolic risk factors in obese adults with low vitamin D levels - results from a randomized trial

Abstract

Background: Low plasma 25-hydroxy-vitamin D (25OHD) is associated with obesity. Vitamin D (VD) may be implicated in obesity and its complications such as insulin resistance, hypertension, and low-grade inflammation. We investigated the effects of VD supplementation on fat distribution and on obesity complications in obese adults with low plasma levels of 25OHD.

Methods: In a double-blind design 52 subjects aged 18 to 50years with BMI>30kg/m(2) and plasma 25OHD <50nmol/l were randomized to 26weeks of treatment with 7000IU of VD daily or placebo. Body composition was assessed by DXA and subcutaneous (SAT) and visceral adipose tissue (VAT), intrahepatic (IHL) and intramyocellular lipids (IMCL) were evaluated by magnetic resonance imaging and magnetic resonance spectroscopy. Insulin resistance (HOMA-IR), blood pressure, plasma lipids, and circulating inflammatory markers were also investigated.

Results: VD treatment increased mean plasma levels of 25OHD from 33nmol/l to 110nmol/l (P<0.0001) and decreased median parathyroid hormone levels from 5.3 to 4.5pmol/l (P<0.01) in the intervention group. Treatment did not change body fat, SAT, VAT, IHL, or IMCL compared with placebo. Neither did treatment affect HOMA, blood pressure, plasma lipids or any of several inflammatory markers investigated including hsCRP.

Conclusion: Increasing 25OHD levels by VD treatment for 26weeks have no effects on obesity complications in obese adults with low baseline plasma 25OHD.

Keywords: Abdominal obesity; Body fat distribution; Inflammation; Insulin resistance; Magnetic resonance imaging; Vitamin D.