People who consumed the most magnesium in foods and from vitamin supplements were about half as likely to develop diabetes over the next 20 years as people who took in the least magnesium, Dr. Ka He of the University of North Carolina at Chapel Hill and colleagues found.
The results may explain in part why consuming whole grains, which are high in magnesium, is also associated with lower diabetes risk. However, large clinical trials testing the effects of magnesium on diabetes risk are needed to determine whether a causal relationship truly exists, the researchers note in Diabetes Care.
It's plausible that magnesium could influence diabetes risk because the mineral is needed for the proper functioning of several enzymes that help the body process glucose, the researchers point out. Studies of magnesium and diabetes risk have had conflicting results, though.
To investigate the link, the researchers looked at magnesium intake and diabetes risk in 4,497 men and women 18 to 30 years old, none of whom were diabetic at the study's outset. During a 20-year follow-up period, 330 of the subjects developed diabetes.
People with the highest magnesium intake, who averaged about 200 milligrams of magnesium for every 1,000 calories they consumed, were 47 percent less likely to have developed diabetes during follow up than those with the lowest intakes, who consumed about 100 milligrams of magnesium per 1,000 calories.
He and colleagues also found that as magnesium intake rose, levels of several markers of inflammation decreased, as did resistance to the effects of the key blood-sugar-regulating hormone insulin. Higher blood levels of magnesium also were linked to a lower degree of insulin resistance.
Increasing magnesium intake may be important for improving insulin sensitivity, reducing systemic inflammation, and decreasing diabetes risk, He and colleagues write. Further large-scale clinical trials are needed to establish causal inference and elucidate the mechanisms behind this potential benefit.