Dietary and plasma magnesium and risk of coronary heart disease among women

Abstract

Background: Magnesium is associated with lower risk of sudden cardiac death, possibly through antiarrhythmic mechanisms. Magnesium influences endothelial function, inflammation, blood pressure, and diabetes, but a direct relation with coronary heart disease (CHD) risk has not been established.

Methods and results: We prospectively examined the association between dietary and plasma magnesium and risk of CHD among women in the Nurses' Health Study. The association for magnesium intake was examined among 86 323 women free of disease in 1980. Information on magnesium intake and lifestyle factors was ascertained every 2 to 4 years through questionnaires. Through 2008, 3614 cases of CHD (2511 nonfatal/1103 fatal) were documented. For plasma magnesium, we conducted a nested case-control analysis, with 458 cases of incident CHD (400 nonfatal/58 fatal) matched to controls (1:1) on age, smoking, fasting status, and date of blood sampling. Higher magnesium intake was not associated with lower risk of total CHD (P-linear trend=0.12) or nonfatal CHD (P-linear trend=0.88) in multivariable models. However, magnesium intake was inversely associated with risk of fatal CHD. The RR comparing quintile 5 to quintile 1 of magnesium intake was 0.61 (95% CI, 0.45 to 0.84; P-linear trend=0.003). The association between magnesium intake and risk of fatal CHD appeared to be mediated partially by hypertension. Plasma magnesium levels above 2.0 mg/dL were associated with lower risk of CHD, although not independent of other cardiovascular biomarkers (RR, 0.67; 95% CI, 0.44 to 1.04).

Conclusions: Dietary and plasma magnesium were not associated with total CHD incidence in this population of women. Dietary magnesium intake was inversely associated with fatal CHD, which may be mediated in part by hypertension.

Figure 1.

Multivariate relative risk of total CHD as a function of plasma magnesium. Data were fitted by a restricted cubic spline Cox proportional hazards model. The 95% confidence intervals are indicated by dashed lines. Models conditioned on matching factors (age, smoking status, month of blood draw, and fasting status) and adjusted for BMI, exercise, alcohol intake, family history of MI, eGFR, menopausal therapy, multivitamin use, intake of omega‐3 fats, polyunsaturated:saturated fat, trans fat, dietary cholesterol, cereal fiber, calcium, potassium, vitamin D, magnesium, baseline hypertension, baseline hypercholesterolemia, baseline diabetes, and concentration of HDL‐C, LDL‐C, hsCRP, adiponectin, and HbA1c. CHD indicates coronary heart disease; BMI, body mass index; MI, myocardial infarction; eGFR, estimated glomerular filtration rate; HDL‐C, high‐density lipoprotein cholesterol; LDL‐C, low‐density lipoprotein cholesterol; hsCRP, high‐sensitivity C‐reactive protein; HbA1c, hemoglobin A1c.