The results of a meta-analysis published in the September, 2011 issue of the journal Diabetes Care found a significantly reduced risk of type 2 diabetes among men and women whose intake of magnesium was relatively high compared to those with a lower intake.
Researchers at Soochow University in China and the University of North Carolina at Chapel Hill reviewed 13 prospective studies that included a total of 536,318 participants. Nine of the studies provided information on the magnesium content of the subjects' diets, two included data on magnesium from diet and supplements, and the remainder provided dietary and total magnesium intake. Study follow-up periods ranged from four to twenty years, during which 24,516 cases of diabetes were diagnosed.
Nine studies uncovered a significant protective effect for increased magnesium intake against the risk of diabetes. A 22 percent lower risk of diabetes was found for those whose intake was highest compared to those whose consumption of the mineral was lowest. Each 100 milligram per day increase in magnesium was associated with a 14 percent lower risk of developing the disease.
Further analysis revealed a more pronounced effect for the mineral among those whose body mass index was more than 25 kg/m2. "It is plausible that high magnesium intake may have greater effects on improving insulin sensitivity in overweight individuals who are prone to insulin resistance," Jia-Yi Dong and colleagues remark.
They note that intracellular magnesium deficiency could lead to disorders of the activity of an enzyme involved in insulin signaling and secretion, resulting in decreased insulin sensitivity in muscle and fat cells. Trial results suggest that supplementing with the mineral can improve glucose control in diabetics as well as insulin sensitivity in nondiabetics.
"To date, large scale, randomized, placebo-controlled trials, which provide the strongest evidence for establishing a causal relation, have not been carried out to directly evaluate the effect of magnesium on diabetes incidence," the authors write. "Given the compelling evidence from the observational studies, such trials are anticipated to draw definitive conclusions. As for public health, increased consumption of magnesium-rich foods, such as whole grains, nuts, and green leafy vegetables, may bring considerable benefits in diabetes prevention, especially in those at high risk."