Magnesium intake, C-reactive protein, and the prevalence of metabolic syndrome in middle-aged and older US women

OBJECTIVE - The aim of this study was to examine whether and to what extent magnesium intake is related to systemic inflammation and the metabolic syndrome. RESEARCH DESIGN AND METHODS - We performed a cross-sectional analysis on data from 11,686 women ≥ 45 years of age participating in the Women's Health Study who were initially free of cardiovascular disease and cancer and had no use of postmenopausal hormones. RESULTS - in age- and BMI-adjusted analyses, magnesium intake was inversely associated with plasma C-reactive protein (CRP) concentrations; CRP concentrations were 12% lower in the highest intake quintile than in the lowest (P for trend < 0.0001). This association was not appreciably altered by further adjustment for other potential confounding variables including dietary factors; the mean CRP concentrations for ascending quintiles of magnesium intake were 1.50, 1.39, 1.35, 1.34, and 1.31 mg/l (P for trend = 0.0003). This inverse association was stronger for women with a BMI ≥ 25 kg/m(2) (P < 0.0001 for interaction) and those who were current or past smokers (P = 0.0009 for interaction). After adjustment for confounding lifestyle and dietary factors, women in the highest quintile of magnesium intake had 27% lower risk of the metabolic syndrome (defined according to the National Cholesterol Education Program criteria) compared with those in the lowest quintile of intake (odds ratio 0.73 [95% CI 0.60-0.88], P for trend = 0.0008). CONCLUSIONS - Our results suggest that magnesium intake is inversely associated with systemic inflammation and the prevalence of the metabolic syndrome in middle-aged and older women.