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Magnesium, Carbs & Diabetes…Is There a Link?

by Ashley Jordan Ferira, PhD, RDN

Recent research from three well-known cohorts, The Nurses’ Health Study (NHS), NHS2 and Health Professionals’ Follow-Up Study (HPFS), reveals that higher magnesium intake is associated with lower risk of type 2 diabetes (T2D), particularly in diets with poor carbohydrate quality.1

Green leafy vegetables, unrefined whole grains, and nuts are richest in magnesium, while meats and milk contain a moderate amount.2 Refined foods, like carbohydrates (carb), are poor sources of magnesium. Diets with poor carb quality are characterized by higher glycemic index (GI), higher glycemic load (GL), and lower fiber intake. These poor carbs require a higher insulin demand.

The typical American diet is low in vegetables and whole grains, resulting in reduced magnesium intake.  The Recommended Daily Allowance (RDA) for magnesium is 310-320 mg/day for adult women and 400-420 mg/day for adult men.3 Half of the US population fails to meet their daily magnesium needs, and hypomagnesemia exists in 1/3 of adults.4-5 Magnesium is needed for normal insulin signaling; current research has linked insufficient magnesium intake to prediabetes, insulin resistance and T2D.4 Increased magnesium intake has been inversely associated with T2D risk in observational studies.6

Collaborators from Tufts University, Harvard University, and Brigham and Women’s Hospital, sought to investigate the impact of magnesium intake, from both dietary and supplemental sources, on the risk of developing T2D in subjects who had diets with poor carb quality and raised GI, GL, or low fiber intake.1 They followed three large prospective cohorts, NHS, NHS2 and HPFS (totaling over 202,700 participants). Dietary intake was quantified by validated food frequency questionnaires (FFQ) every 4 years, and T2D cases were captured via questionnaires. Over 28 years of follow-up, there were 17,130 cases of T2D.

Major study findings included:1

  • Increased magnesium intake (390-470 mg/day) was associated with a 15% lower risk of developing T2D compared to lower magnesium intake (229-280 mg/day)
  • Risk of T2D was reduced by 4% with each additional 50 mg/day of magnesium intake
  • In diets with poor carb quality, magnesium was more strongly, and inversely, associated with T2D

Consuming a poor carb quality diet over the long-term may increase the demand on pancreatic beta cells, contributing to beta cell exhaustion and failure, resulting in increased risk for diabetes. Magnesium may help mitigate this process. Low magnesium may not only be a cause of diabetes, but also a consequence. 

Similar to the US population estimates, 40-50% of study participants had inadequate magnesium intake. A healthful, varied diet and supplemental magnesium (especially in diets that restrict or exclude carbohydrates, dairy or meat) are essential to ensure sufficient daily magnesium intake.

Why is this Clinically Relevant?

  • Magnesium is an essential macromineral that is under-consumed by at least ½ of the US population
  • Magnesium is required for normal insulin signaling and action
  • Poor carbohydrate diet quality is characterized by higher GI and GL as well as lower fiber intake leading to increased insulin demand
  • Inadequate magnesium intake and status are inversely associated with diabetes risk
  • HCPs can help patients achieve magnesium sufficiency through a healthful diet of unrefined whole grains, green leafy vegetables, legumes, meats, and dairy
  • If dietary input and/or blood level of magnesium are found to be insufficient, a magnesium supplementation regimen should be considered

Link to Abstract


  1. Hruby A, Guash-Ferré M, Bhupathiraju SN, Manson JE, Willett WC, McKeown NM, Hu FB. Magnesium intake, quality of carbohydrates, and risk of type 2 diabetes: results from three U.S. cohorts. Diab Care. 2017;40(12):1695-1702.
  2. Oregon State University. Linus Pauling Institute. Micronutrient Information Center. Magnesium. Accessed December 6, 2017.
  3. Institute of Medicine (IOM). Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. Washington, DC: National Academy Press, 1997.
  4. U.S. Department of Health and Human Services and U.S. Department of Agriculture. Scientific Report of the 2015 Dietary Guidelines Advisory Committee. Advisory Report to the Secretary of Health and Human Services and the Secretary of Agriculture. 2015. Accessed November 9, 2017,
  5. Hruby A, McKeown NM. Magnesium deficiency: what is our status? Nutr Today.2016;51:121-128.
  6. Gommers LMM, Hoenderop JGJ. Hypomagnesemia in type 2 diabetes: a vicious circle? Diabetes 2016;65:3-13.

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