By:  Talking Nutrition Editors

Magnesium is an essential mineral needed by the body and is involved with many functions, including more than 300 enzymatic reactions.1 Low magnesium intake is associated with an increased risk of variety of chronic diseases;^2-6 however, its role in the prevention of osteoporotic fracture is less clear.⁷ A recent meta-analysis8 found that higher dietary magnesium intake was not associated with decreased fracture risk. Indeed, in some studies magnesium intake above the RDA was associated with a higher risk for fractures. However, in contrast, cross-sectional studies have shown a significant association between higher magnesium intake and bone mineral density. Magnesium may also have a beneficial effect on inflammation and oxidative stress, two important risk factors for osteoporosis.  

In a new study,⁸ data on magnesium intake and bone fracture were obtained from subjects enrolled in the Osteoarthritis Initiative over a follow-up period of eight years. Patients were at high risk for knee osteoarthritis. Estimates of dietary magnesium intake were obtained through a food frequency questionnaire recorded during the baseline visit of the Osteoarthritis Initiative. The cohort was divided into quintiles of magnesium intake according to gender using 205, 269, 323, and 398 mg per day for men and 190, 251, 306 and 373 mg per day for women. Overall in the cohort there were 3765 participants with a mean age of 60.6 years. 

The mean intake of magnesium was 295 mg per day. Only 27% of the whole cohort reached the corresponding magnesium RDA (420 mg/d for men and 320 mg/d for women, respectively). After a mean follow-up period of 6.2 years, 560 individuals develop a new skeletal fracture. Both men and women with higher magnesium intake reported a significantly lower incidence of fractures compared with those having the lowest magnesium intake. After adjusting for 14 potential confounders at baseline, and using those with the lowest magnesium intake as the reference group, men and women in the fifth quintile (highest magnesium intake group) reported a 53% lower risk for bone fracture. If the subjects were divided on the basis of the RDA for magnesium, only women reaching the RDA for magnesium had a significant reduction in fracture risk. Total magnesium intake, modeled as a continuous variable, however, was not associated with any decrease risk of fracture at follow-up.  

These findings are notable because the investigators found that only ¼ of the participants in the Osteoarthritis Initiative reported consuming at least the RDA level for magnesium. This study is the first reporting a clear and significant association between higher magnesium intake and reduction in fractures in both men and women. Since magnesium has a myriad of functions in the body, additional studies elucidating the molecular mechanism of action of higher magnesium intake on bone fracture are needed.