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In the news: Higher Magnesium Intake Lowers Type 2 Risk in Those with High GI Diet

Magnesium, Glycemic Index & Disease Risk

As the global prevalence of type 2 diabetes increases, so will the number of people with diabetic retinopathy and other micro-vascular complications of the disease. Prevention of diabetes by addressing modifiable risk factors such as obesity, poor diet, and physical inactivity is paramount, although achieving sustainable behavior change is often difficult.

Based on the newly published findings of Tufts and Harvard researchers, one fairly simple step toward type 2 risk reduction may be to ensure adequate intake of magnesium. Recognized as a shortfall nutrient in the Scientific Report of the 2015 Dietary Guidelines Advisory Committee, nearly 50% of the US population has inadequate magnesium intake.

Hypomagnesemia tends to be more pronounced in pre-diabetes, insulin resistance or diabetes. Low serum levels have been associated with increased risk of prediabetes and diabetes via insulin resistance pathways. Magnesium is integral to insulin secretion and sensitivity. It’s been shown that low levels of magnesium impair insulin function, while the compensatory overproduction of insulin that occurs with insulin resistance depletes magnesium levels.

The new research, which combined cohorts from three large studies followed for 28 years, found that higher magnesium intake is associated with lower risk of type 2, especially in those consuming high glycemic index (GI) diets- diets low in fiber and high in processed carbohydrates such as white flour and sugar. The high GI diet is a common dietary pattern in the US, and one that has been associated not only with the risk of diabetes, but with cataract and early AMD as well.

Design and Methods

This analysis used data from the Nurses’ Health Study (n= 69,176), the Nurses’ Health Study 2 (n= 91,471) Health Professionals’ Follow-Up Study (n= 42,096). In these studies, dietary intake was assessed from food frequency questionnaires every 4 years. Magnesium intake was from food and supplements. Type 2 diabetes was ascertained by biennial and supplementary questionnaires.

Multivariate hazard ratios of magnesium intake and incident diabetes were calculated and adjusted for multiple factors including age, BMI, family history of diabetes, physical activity, smoking, hypertension, hypercholesterolemia, energy intake, trans fatty acids, and other factors. The joint associations of magnesium and carbohydrate quality on diabetes risk were also considered.

Results

Over 28 years of follow-up, 17,130 incident cases of type 2 diabetes were documented.

In pooled analyses across the three cohorts1, those with the highest magnesium intake had 15% lower risk of type 2 diabetes compared with those with the lowest
intake (pooled multivariate HR in quintile 5 vs. 1:0.85 [95% CI 0.80-0.91], P < 0.0001).

Higher magnesium intake was more strongly associated with lower risk of type 2 diabetes among participants with high GI or low cereal fiber than among those with
low GI or high cereal fiber (both P interaction <0.001).

Conclusion

Higher magnesium intake is associated with lower risk of type 2 diabetes, especially in the context of lower carbohydrate-quality diets.

Comments

These results are consistent with a large body of observational literature on the beneficial role of magnesium on type 2 diabetes risk. A recent meta-analysis of 25 prospective cohort studies, for example,
indicated a linear dose-response relationship between magnesium intake and type 2 diabetes, with an 8-13% lower risk per 100 mg/day increase in intake. The recommended daily magnesium intake for adults is 420 mg (men) and 320 mg (women). Good food sources include green leafy vegetables such as spinach, legumes, nuts, seeds, and whole grains.

References

1. Hruby A, et al. Magnesium Intake, Quality of Carbohydrates, and Risk of Type 2 Diabetes: Results From Three U.S. Cohorts. Diabetes Care 40:1695-1702, 2017.