Preventive cardiology
Dietary Magnesium Intake and Risk of Cardiovascular Disease Among Women

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This study assessed the hypothesis that greater magnesium intake is associated with reduced risk for cardiovascular disease (CVD), including myocardial infarction (MI) and stroke, in a large prospective cohort of women. In 1993, a semi-quantitative food frequency questionnaire was used to assess magnesium intake in 39,876 female health professionals aged 39 to 89 years who had no history of CVD or cancer. During a median of 10 years of follow-up, 1,037 incident cases of CVD were identified, including 280 nonfatal MIs and 368 strokes. After adjustment for age and randomized treatment status, magnesium intake was not significantly associated with risk for incident CVD. Comparing the highest quintile of magnesium intake (median 433 mg/day) with the lowest quintile (median 255 mg/day), the relative risks were 0.87 (95% confidence interval [CI] 0.72 to 1.05, p for trend = 0.24) for total CVD, 0.88 (95% CI 0.70 to 1.12, p for trend = 0.34) for coronary heart disease (CHD), 1.03 (95% CI 0.72 to 1.49, p for trend = 0.96) for nonfatal MI, 1.11 (95% CI 0.61 to 2.00, p for trend = 0.95) for CVD death, and 0.87 (95% CI 0.64 to 1.18, p for trend = 0.55) for total stroke. Additional adjustment for other CVD risk factors did not materially change the observed null associations. In conclusion, the results do not support the hypothesis that magnesium intake reduces the development of CHD, although a modest inverse association with stroke cannot be ruled out.

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Study population

The Women’s Health Study is a randomized, double-blind, placebo-controlled trial designed to evaluate the balance of benefits and risks of small-dose aspirin and vitamin E in the primary prevention of CVD and cancer.4 We randomized a total of 39,876 female health professionals aged 39 to 89 years who were free of coronary heart disease (CHD), stroke, and cancer (except for nonmelanoma skin cancer). Of them, 98% provided detailed information about their diets at baseline, completing a 131-item

Results

In the present study, dietary sources accounted for about 96% of the total intake of magnesium. The median intake of magnesium was 326 mg/day for our cohort of middle-aged women, which is close to the recommended dietary allowance of 320 mg/day for adult women.12 There was an approximately 1.7-fold difference in total magnesium intake between the highest and lowest quintiles of the study population (median 433 mg/day in the highest quintile vs 255 mg/day in the lowest quintile; Table 1). Women

Discussion

In this large prospective study of middle-aged and older American women, we found no significant association between magnesium intake and the incidence of total CVD, CHD, nonfatal MI, or stroke, although there was a suggestion of a lower risk for total stroke and ischemic stroke associated with larger intakes of magnesium.

Magnesium intake has long been believed to be protective against CVD, mortality, or arrhythmias after CVD.2 Abnormalities in intracellular magnesium homeostasis have been

Acknowledgment

We are indebted to the 39,876 dedicated and committed participants of the Women’s Health Study. We also acknowledge the contributions of the entire staff of the Women’s Health Study.

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    This study was supported by Grants DK66401, CA-47988, HL-43851, and HL-65727 from the National Institutes of Health, Bethesda, Maryland. Dr. Song was supported by the Irene and Fredrick J. Stare Nutrition Education Fund from the Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts.

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