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Vitamin D deficiency increases risk for metabolic syndrome in Chinese youths
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Adolescents and young adults with vitamin D deficiency are nearly 2.5 times more likely to have metabolic syndrome vs. those without vitamin D deficiency, according to findings from an ongoing study of participants in China.
“Due to increased sedentary lifestyle, it has been suggested that vitamin D deficiency is more common in young populations, even among those with abundant sun exposure,” Steven M. Willi, MD, associate professor of pediatrics at the Children’s Hospital of Philadelphia, and colleagues wrote in the study background. “Nonetheless, the relationship between vitamin D deficiency and obesity, diabetes and [metabolic syndrome] remains controversial, as some studies reveal an association while others do not.”
Researchers analyzed data from 559 adolescents and young adults aged 14 to 28 years participating in a 10-year follow-up to the Beijing Child and Adolescent Metabolic Syndrome study, an ongoing, prospective study of obesity and associated cardiometabolic conditions in a sample of school-aged children. Follow-up for the cohort began in 2012.
Researchers assessed anthropometric measurements, including height, weight, neck and waist circumference and body fat percentage, as well as systolic and diastolic blood pressure and BMI. Blood samples were obtained after an overnight fast, and all participants underwent a 2-hour oral glucose tolerance test. Researchers measured levels of vitamin D, glucose, insulin and lipids.
Insulin resistance was measured via homeostatic model assessment of insulin resistance, fasting insulin, and the Matsuda insulin sensitive index. Vitamin D deficiency was characterized as a 25-hydroxyvitamin D level of less than 20 ng/mL; severe deficiency was 25-(OH)D less than 11 ng/mL. Metabolic syndrome was defined as having at least three of the following: central obesity (waist circumference > 90 cm for males or > 80 cm for females), BP of at least 130 mm Hg/85 mm/Hg, HDL cholesterol less than 1.03 mmol/L for males or less than 1.29 mmol/L for females, triglycerides of at least 1.7 mmol/L, fasting blood glucose of at least 5.6 mmol/L and/or 2-hour blood glucose of at least 7.8 mmol/L.
Within the cohort, mean 25-(OH)D level was 15.2 ng/mL. The prevalence of vitamin D deficiency was 78.3% and was higher in females (88.9%) vs. males (68.7%).
More than 11% of study participants had metabolic syndrome, according to the researchers. Those with metabolic syndrome had higher BMI, neck circumference, percent body fat, total cholesterol, LDL cholesterol and HOMA-IR levels vs. those without (P < .01 for all). Moreover, participants with metabolic syndrome had lower vitamin D levels vs. those without metabolic syndrome (mean, 14.6 ng/mL vs. 15.3 ng/mL). Although participants with metabolic syndrome appeared to have a higher prevalence of vitamin D deficiency (80.7% vs. 77.8% in those without metabolic syndrome) and severe vitamin D deficiency (28.1% vs. 24.7%), these differences were not considered statistically significant, according to researchers.
An analysis adjusted for age, sex and season revealed inverse correlations between vitamin D level and percent body fat (P = .043), neck circumference (P = .001), LDL cholesterol (P = .039), FBG (P = .033) and OGTT (P = .003). Participants with obesity, high triglycerides, type 2 diabetes and metabolic syndrome had lower vitamin D levels vs. those without these conditions (P < .05 for all), according to researchers.
An analysis adjusted for potential confounding factors showed that metabolic syndrome was 2.5 times more likely in participants in the lowest vitamin D tertile compared with those in the highest vitamin D tertile (OR = 2.48; 95% CI, 1.13-5.45).
“Our study demonstrated a very high prevalence of vitamin D deficiency among youth at increased risk for [metabolic syndrome], as well as an inverse relationship between vitamin D levels and various components of the [metabolic syndrome],” the researchers wrote. “Our finding suggested that effective sun exposure and vitamin D supplementation should be encouraged in young people, particularly those with increased cardiometabolic risk.” – by Jennifer Byrne
Disclosures: The authors report no relevant financial disclosures.
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