Magnesium intake, C-reactive protein, and the prevalence of metabolic syndrome in middle-aged and older U.S. 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 > or =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 > or =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.