Plasma 25-hydroxyvitamin D concentration and metabolic syndrome among middle-aged and elderly Chinese individuals.

OBJECTIVE: To evaluate the association between 25-hydroxyvitamin D [25(OH)D] and metabolic syndrome in the Chinese population. RESEARCH DESIGN AND METHODS: Plasma 25(OH)D was measured in a cross-sectional sample of 1,443 men and 1,819 women aged 50-70 years from Beijing and Shanghai. Metabolic syndrome was defined according to the updated National Cholesterol Education Program Adult Treatment Panel III criteria for Asian Americans. Fasting plasma glucose, insulin, lipid profile, A1C, and inflammatory markers were measured. RESULTS: The geometric mean of plasma 25(OH)D was 40.4 nmol/l, and percentages of vitamin D deficiency [25(OH)D <50 nmol/l] and insufficiency [50 or=57.7 nmol/l), the odds ratio for metabolic syndrome in the lowest quintile (or=24 kg/m(2)) but not in their normal-weight counterparts (test for interaction: P = 0.0363 and 0.0187 for insulin and HOMA-IR, respectively). CONCLUSIONS: Vitamin D deficiency is common in the middle-aged and elderly Chinese population, and a low 25(OH)D level is significantly associated with an increased risk of having metabolic syndrome and insulin resistance. Prospective studies and randomized clinical trials are warranted to determine the role of 25(OH)D in the development of metabolic syndrome and related metabolic diseases.