Abstract
ObjectiveDecreased serum vitamin D level is a common observation in obese adults. Since no Chinese population-based study has yet evaluated the relationship between serum vitamin D levels and the accurate adiposity variables, this study investigated the association of serum vitamin D (assessed by 25-hydroxyvitamin D3 [25(OH)D3]) levels with precise body fat content and distribution in a cohort of Chinese men.MethodsSerum samples were collected from a total of 567 men with normal glucose tolerance (NGT) for assessment by electrochemiluminescence immunoassay to measure 25(OH)D3 levels. In addition, each participant underwent bioelectrical impedance analysis to quantify total body fat and magnetic resonance imaging to measure visceral fat area (VFA) and subcutaneous fat area (SFA).ResultsOverweight/obese (BMI ≥25 kg/m2) subjects had significantly lower serum 25(OH)D3 levels than non-overweight/non-obese (BMI <25 kg/m2) subjects (P = 0.029). Greater fat mass and VFA were accompanied by a downward trend in serum 25(OH)D3 levels (P for trend <0.01). Among overweight/obese subjects, those with body fat percent ≥25% also had significantly lower serum 25(OH)D3 levels (P <0.05). Moreover, participants with VFA ≥80 cm2 had significantly lower serum 25(OH)D3 (P <0.05), regardless of BMI value. VFA was independently correlated with serum 25(OH)D3 levels (β = −0.023, P <0.001), even after adjustments for confounding factors. In addition, serum 25(OH)D3 levels were found to decrease by 0.26 ng/mL per 10 cm2 increment of VFA.ConclusionsSerum 25(OH)D3 levels were inversely associated with VFA in Chinese men with NGT.
Highlights
The primary biological role of vitamin D, a lipid-soluble vitamin, is the regulation of calcium and phosphorus metabolism; as such, proper levels of vitamin D are critical for establishment of bone health and its maintenance throughout life [1]
When high-dose vitamin D was delivered as a dietary supplement, along with high whey protein and calcium, male Wistar rats experienced a reduction in fat mass and an increase in lean mass [4]
Consistent with the experimental studies, clinical evidence has indicated that serum 25(OH)D levels decrease significantly in obese subjects and has shown that this decrease is closely correlated with fat distribution [6,7]
Summary
The primary biological role of vitamin D, a lipid-soluble vitamin, is the regulation of calcium and phosphorus metabolism; as such, proper levels of vitamin D are critical for establishment of bone health and its maintenance throughout life [1]. Recent studies have indicated that perturbed vitamin D status may contribute to obesity, metabolic syndrome and cardiovascular disease [2]. As the main circulating form of vitamin D, serum 25hydroxyvitamin D [25(OH)D], consisted of 25(OH)D2 and 25(OH)D3, is used as a clinical marker to evaluate vitamin D nutritional status. Consistent with the experimental studies, clinical evidence has indicated that serum 25(OH)D levels decrease significantly in obese subjects and has shown that this decrease is closely correlated with fat distribution [6,7]. Still other studies have implicated the decreased level of serum 25(OH)D as a risk factor for obesity and its related metabolic disorders [8]
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