Magnesium Intake from Food and Supplements Is Associated with Bone Mineral Density in Healthy Older White Subjects

Objectives: To determine whether magnesium intake from supplemental and dietary sources is associated with bone mineral density (BMD) in older men and women. Design: Cross-sectional. Setting: Memphis, Tennessee, and Pittsburgh, Pennsylvania. Participants: Two thousand thirty-eight older black and white men and women aged 70 to 79 at baseline enrolled in the Health, Aging and Body Composition Study. Measurements: Dietary intake of magnesium was assessed using a semiquantitative food frequency questionnaire, and supplement data were collected based on a medication inventory. BMD of the whole body was obtained using a fan-beam densitometer. Additional covariates included age, body mass index (BMI), smoking status, alcohol use, physical activity, estrogen use, and supplemental calcium (Ca) and vitamin D use. Results: In white, but not black, men and women, magnesium intake was positively associated with BMD of the whole body after adjustment for age, self-report of osteoporosis or fracture in adulthood, caloric intake, Ca and vitamin D intake, BMI, smoking status, alcohol intake, physical activity, thiazide diuretic use, and estrogen use in women (P=.05 for men and P=.005 for women). BMD was 0.04 g/cm2 higher in white women and 0.02 g/cm2 higher in white men in the highest than in the lowest quintile of magnesium intake. Conclusion: Greater magnesium intake was significantly related to higher BMD in white women and men. The lack of association observed in black women and men may be related to differences in Ca regulation or in nutrient reporting.