Magnesium intake, bone mineral density, and fractures: results from the Women's Health Initiative Observational Study.
BACKGROUND
Magnesium is a necessary component of bone, but its relation to osteoporotic fractures is unclear.


OBJECTIVE
We examined magnesium intake as a risk factor for osteoporotic fractures and altered bone mineral density (BMD).


METHODS
This prospective cohort study included 73,684 postmenopausal women enrolled in the Women's Health Initiative Observational Study. Total daily magnesium intake was estimated from baseline food-frequency questionnaires plus supplements. Hip fractures were confirmed by a medical record review; other fractures were identified by self-report. A baseline BMD analysis was performed in 4778 participants.


RESULTS
Baseline hip BMD was 3% higher (P < 0.001), and whole-body BMD was 2% higher (P < 0.001), in women who consumed >422.5 compared with <206.5 mg Mg/d. However, the incidence and RR of hip and total fractures did not differ across quintiles of magnesium. In contrast, risk of lower-arm or wrist fractures increased with higher magnesium intake [multivariate-adjusted HRs of 1.15 (95% CI: 1.01, 1.32) and 1.23 (95% CI: 1.07, 1.42) for quintiles 4 and 5, respectively, compared with quintile 1; P-trend = 0.002]. In addition, women with the highest magnesium intakes were more physically active and at increased risk of falls [HR for quintile 4: 1.11 (95% CI: 1.06, 1.16); HR for quintile 5: 1.15 (95% CI: 1.10, 1.20); P-trend < 0.001].


CONCLUSIONS
Lower magnesium intake is associated with lower BMD of the hip and whole body, but this result does not translate into increased risk of fractures. A magnesium consumption slightly greater than the Recommended Dietary Allowance is associated with increased lower-arm and wrist fractures that are possibly related to more physical activity and falls.
Department of Human Nutrition, College of Education and Human Ecology (TSO) and the Division of Endocrinology, Diabetes, and Metabolism, College of Medicine (NA and RDJ), The Ohio State University, Columbus, OH (TSO); the Fred Hutchinson Cancer Research Center, Seattle, WA (JCL and AZL); the Nationwide Children's Hospital, Columbus, OH (SB-T); the Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA (JAC); the Epidemiology and Biostatistics Division, University of Arizona, Tucson, AZ (ZC); and the Departments of Social and Preventive Medicine and Gynecology-Obstetrics, University at Buffalo, Buffalo, NY (JW-W).
Tonya S
TS
Orchard
Joseph C
JC
Larson
Nora
N
Alghothani
Sharon
S
Bout-Tabaku
Jane A
JA
Cauley
Zhao
Z
Chen
Andrea Z
AZ
LaCroix
Jean
J
Wactawski-Wende
Rebecca D
RD
Jackson
D000368:Aged; D005260:Female; D006801:Humans; D008875:Middle Aged; D001842:Bone and Bones / Q000378:metabolism; D015519:Bone Density; D015331:Cohort Studies; D004032:Diet / Q000009:adverse effects; D019587:Dietary Supplements / Q000009:adverse effects; D006620:Hip Fractures / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D015994:Incidence; D008274:Magnesium / Q000009:adverse effects / Q000378:metabolism; D008275:Magnesium Deficiency / Q000503:physiopathology; D008499:Medical Records; D015663:Osteoporosis, Postmenopausal / Q000178:diet therapy / Q000503:physiopathology; D058866:Osteoporotic Fractures / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D014953:Wrist
D008274:Magnesium