Dietary magnesium intake, bone mineral density and risk of fracture: a systematic review and meta-analysis

Dietary magnesium intake has been related to osteoporosis and risk of fractures in earlier studies; however, findings were conflicting. This meta-analysis indicated that high magnesium intake was not associated with increased risk of fracture; however, a positive marginally significant correlation was found between magnesium intake and bone mineral density (BMD) in total hip as well as in femoral neck. Although there is some evidence on the association between magnesium intake, BMD and fractures, no previous study has summarized findings in this regard. We aimed to systematically review the current evidence on this association and to perform a meta-analysis of observational studies. We searched MEDLINE, Scopus, EMBASE and Google Scholar up to January 2015 for studies that examined the relationship between magnesium intake and BMD or fracture. Studies that had reported correlation coefficients between magnesium intake and BMD or those that reported odds ratios (ORs) or relative risks (RRs) for risk of fracture in different sites were included. In total, 12 studies were included in the meta-analysis. We found that high intakes of magnesium were not significantly associated with risk of total hip fracture (summary effect size 1.92; 95 % CI 0.81, 4.55) or total fractures (1.01; 0.94-1.07). Combining four effect sizes, a positive marginally significant correlation was observed between magnesium intake and total BMD (pooled r 0.16; 95 % CI 0.001, 032). Based on nine effect sizes, we found a marginally significant association between magnesium intake and femoral neck BMD (0.14; 0.001, 0.28). However, no significant correlation was found between magnesium intake and BMD in lumbar spine (0.09; -0.01, 0.19). We found that high intakes of magnesium were not associated with increased risk of hip and total fractures. There was a positive marginally significant correlation between magnesium intake and BMD in femoral neck and total hip. No significant correlations were observed between magnesium intake and BMD in lumbar spine.