Magnesium Lowers Type 2 Diabetes Risk

Magnesium-Rich Foods Appear to Be Protective Regardless of Weight, Activity Level

Medically Reviewed by Brunilda Nazario, MD on December 23, 2003
From the WebMD Archives

Dec. 23, 2003 -- Want to reduce your diabetes risk? Make a spinach salad your next meal, with a side of whole-wheat bread or almonds.

Two new studies suggest magnesium-rich foods like these can significantly lower the risk of developing type 2 diabetes, even in obese people who are at high risk for the disease. Earlier studies linked magnesium deficiency with an increased risk for diabetes. The latest findings carry this observation further by confirming the mineral's role in protecting against the disease.

Almost 170,000 People Studied

The larger of the two studies involved roughly 85,000 women and 42,000 men who completed dietary intake questionnaires every two to four years. The smaller study had a similar design and involved just under 40,000 women who were 45 or older. Both studies were conducted by researchers from Harvard University, and both are published in the January 2004 issue of the journal Diabetes Care.

In the larger study, the female subjects were followed for 18 years and the men for 12, during which time roughly 5,400 people developed type 2 diabetes. Even after taking into account diabetes risk factors such as age, weight, physical activity, smoking, and family history, those with the highest dietary levels of magnesium were found to have significantly lower risk for type 2 diabetes compared with those with the lowest magnesium levels.

The risk remained significant even after the researchers adjusted for other dietary variables associated with type 2 diabetes risk, such as fat fiber and glycemic load. The risk reduction was similar in the second study.

Eat Your Vegetables

So if eating leafy green vegetables, nuts, and other magnesium-rich foods is good, is taking magnesium in supplement form an even better way to protect against diabetes? Diabetes expert Jerry Nadler, MD, says it not clear whether supplemental magnesium is beneficial, and it could even be harmful. This is especially true for people with kidney disease.

"It is very hard to get too much magnesium from food sources, but that is not true with supplements," he tells WebMD. "The main message from these studies is that people should get the recommended amount of magnesium, which most of the population is probably not getting."

In fact, it is estimated that well more than 50% of people in the U.S. get the recommended daily allowance of the mineral of between 300 and 400 mg, although this varies with sex and age. The average magnesium intake over the entire follow-up was 290 mg/day in women but ranged from 79-1,110 mg/day; in men, the average intake was 349 mg/day but ranged from 102-1,593 mg/day.

Researchers from the larger study concluded that people who are not magnesium deficient probably won't derive as much benefit from adding more of the mineral to their diet as people who are deficient. But they added that for those in the latter category, eating a magnesium-rich diet should help reduce their diabetes risk regardless of their other risk factors for the disease.

Magnesium-rich foods include the following:



Magnesium (mg)

100% Bran Cereal (e.g. All Bran)

1/2 cup


Shredded wheat

2 biscuits


Spinach, chopped

1/2 cup cooked



1 ounce (2 almonds)


Oat bran

1/2 cup dry


"Our (study) suggests that higher magnesium consumption is likely beneficial for all groups, regardless of [whether they are overweight], physical activity levels, and hypertension status," researcher Ruy Lopez-Ridaura, MD, and colleagues from the Harvard School of Public Health write.

More Study Needed

In an editorial published with the two studies, Nadler called for more research to confirm the magnesium-diabetes link. He wrote that the epidemic of obesity and type 2 diabetes in the U.S. makes the identification of cost-effective strategies to prevent the disease a top priority.

In the meantime, he says, most people could benefit from adding more magnesium-rich foods to their diets.

"These are foods that people should be eating anyway for a variety of health reasons," he tells WebMD.

Show Sources

SOURCES: Lopez-Ridaura, R. Diabetes Care, January 2004; vol 27: pp 134-140. Ruy Lopez-Ridaura, MD, department of nutrition, Harvard School of Public Health, Boston. Jerry L. Nadler, MD, head of the division of endocrinology and metabolism, University of Virginia.

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