The analysis of prospective cohort studies, by researchers at Stockholm's Karolinska Institutet, reports that for every 100 milligram increase in magnesium intake, the risk of developing type-2 diabetes decreased by 15 per cent.
"Findings from this meta-analysis of cohort studies indicate that increased intake of magnesium may reduce the incidence of type-2 diabetes.
This observational evidence should be treated as compelling but not definitive," wrote authors Susanna Larsson and Alicia Wolk in the Journal of Internal Medicine .
Dietary sources of magnesium include green, leafy vegetables, meats, starches, grains and nuts, and milk.
Earlier dietary surveys show that a large portion of adults does not meet the RDA for magnesium (320 mg per day for women and 420 mg per day for men).
Larsson and Wolk identified seven studies looking at the link between magnesium intake from food or food plus supplements and the risk of type-2 diabetes.
This gave the researchers a total of 286,668 participants and 10,912 cases of type-2 diabetes.
Six of the studies showed a statistically significant inverse association, with every 100 mg per day increase in magnesium intake linked to a 15 per cent decrease in type-2 diabetes risk.
"The potential protective role of magnesium intake against type-2 diabetes may be due to improvement of insulin sensitivity," said the reviewers.
"Studies in animals have demonstrated an adverse effect of magnesium deficiency on glucose-induced insulin secretion and insulin-mediated glucose uptake.
In contrast, magnesium supplementation was shown to prevent fructose-induced insulin resistance and reduce the development of diabetes in a rat model of spontaneous type-2 diabetes."
They concluded that while it is too early to recommend magnesium supplements for type-2 diabetes prevention, increased consumption of magnesium-rich food "seems prudent."
An estimated 19 million people are affected by diabetes in the EU 25, equal to four per cent of the total population.
This figure is projected to increase to 26 million by 2030.
In the US, there are over 20 million people with diabetes, equal to seven per cent of the population.
The total costs are thought to be as much as $132 billion, with $92 billion being direct costs from medication, according to 2002 American Diabetes Association figures.
Source: Journal of Internal Medicine (Blackwell Publishing) Published on-line, doi: 10.1111/j.1365-2796.2007.01840.x "Magnesium intake and risk of tpe-2 diabetes: a meta-analysis" Authors: S.C. Larsson, A. Wolk