Magnesium intake is associated with greater bone mineral density but not protective against fractures in the Women's Health Initiative Observational Study (WHI‐OS)

Abstract

Magnesium (Mg) is a component of healthy bone but the relation of Mg to fracture risk is unclear. The aim of this study was to examine Mg intake as a risk factor for osteoporotic fractures as well as altered bone mineral density (BMD).This prospective cohort study included 73,684 postmenopausal women from the WHI‐OS. Mg intake was estimated from baseline food frequency questionnaires plus supplement use. Hip fractures were confirmed by medical record review; other fractures were self‐reported.Incidences and relative risks of hip and total fractures were not significantly different across quintiles (Q) of Mg intake. However, risk of lower arm/wrist fractures increased with increasing Mg [multi‐variate adjusted hazard ratios (HR) Q4: 1.15 (95% CI 1.01, 1.32) and Q5: 1.23 (95% CI 1.07, 1.42); p for trend 0.048]. Additionally, women in Q4 and Q5 were more physically active and were at higher risk for falls (HR Q4: 1.11; 95% CI 1.06, 1.16; and Q5: 1.15; 95% CI 1.10, 1.20; p for trend <0.001). There was a 3% higher hip BMD, and a 2% higher whole body BMD in women consuming >;422.5 mg/d of Mg versus <206.5 mg/d (p <0.001).In conclusion, lower BMD of the hip and whole body were associated with lower Mg intake but this did not translate into increased risk of fractures. Mg consumption slightly greater than the RDA was associated with increased falls and lower arm/wrist fractures, possibly related to more physical activity in this group of women.