Abstract: Increasing evidence has suggested an association between dietary magnesium intake and metabolic syndrome. However, previous research examining dietary magnesium intake and metabolic syndrome has produced mixed results. Our objective was to determine the relationship between dietary magnesium intake and metabolic syndrome in the adult population using a dose-response meta-analysis. We searched the PubMed, Embase and the Cochrane Library databases from August, 1965, to May, 2014. Observational studies reporting risk ratios with 95% confidence intervals (CIs) for metabolic syndrome in ≥3 categories of dietary magnesium intake levels were selected. The data extraction was performed independently by two authors, and the quality of the studies was evaluated using the Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS). Based on eight cross-sectional studies and two prospective cohort studies, the pooled relative risks of metabolic syndrome per 150 mg/day increment in magnesium intake was 0.88 (95% CI, 0.84–0.93; I2 = 36.3%). The meta-regression model showed a generally linear, inverse relationship between magnesium intake (mg/day) and metabolic syndrome. This dose-response meta-analysis indicates that dietary magnesium intake is significantly and inversely associated with the risk of metabolic syndrome. However, randomized clinical trials will be necessary to address the issue of causality and to determine whether magnesium supplementation is effective for the prevention of metabolic syndrome.
Alex’s Notes: Low serum magnesium levels have been associated with several metabolic syndrome risk factors such as hyperglycemia, hypertension, hypertriglyceridemia, and insulin resistance. Surprisingly, even waist circumference is independently associated with low magnesium levels. It makes sense, really. Magnesium is a necessary cofactor for several enzymes involved with glucose metabolism, most notably those involved in insulin receptor activity.
In the current meta-analysis, ten independent observational studies (8 cross-sectional; 2 prospective cohort) with a total of 30.092 persons aged 18-72 years were included for review. The majority were conducted in healthy populations, while two were hospital-based. The results revealed that for every additional 150mg of magnesium consumed per day, risk of metabolic syndrome decreased by 12%. During subgroup analyses, there were no significant differences for study design, location, population base, sex, or age. Interestingly, the risk reduction did change depending on how magnesium intake was assessed. The risk reduction for food frequency questionnaires (FFQ), 24-hour recalls, and 3-day food logs were 9, 14, and 28%, respectively. Clearly all three methods have their flaws and limitations.
So what foods are high in magnesium? The number one spot goes to rice bran! But since no one enjoys arsenic, the next best options are wheat bran, cocoa powder, pumpkin seeds, Brazil nuts, and sesame seeds. Meat, dairy, and eggs are overall poor sources, with nuts and seeds being the best bet. However, on a caloric rather than weight basis, fibrous vegetables are the winners.