Higher Magnesium Links With Better Bariatric Surgery Outcomes

Miriam E. Tucker, for Medscape

May 09, 2022

Researchers published the study covered in this summary on researchsquare.com as a preprint that has not yet been peer reviewed.

Key Takeaways

  • In patients with type 2 diabetes who underwent bariatric surgery, higher serum magnesium levels at baseline and 1-year following bariatric surgery were associated with better glycemic control and a greater likelihood of diabetes remission during the year after bariatric surgery.

Why This Matters

  • After bariatric surgery, micronutrient deficiencies are one of the most common and compelling problems, and supplementation is recommended.

  • Abnormally low levels of serum magnesium are relatively common among patients with diabetes, especially those with inadequately controlled glycemia.

  • Prior reports have documented that low dietary magnesium intake is associated with an increased risk of developing type 2 diabetes and diminished glycemic control in those with type 2 diabetes.

  • Bariatric surgery remains the most effective treatment for severe obesity and can lead to improvement or even resolution of type 2 diabetes.

  • No known previous study has assessed the relationship between magnesium supplementation, magnesium serum levels, and glycemic control in patients with type 2 diabetes both before and after bariatric surgery, nor the relationships between these measures and diabetes remission rates.

Study Design

  • This was a retrospective, observational study of 403 patients (79% women) with obesity (body mass index ≥ 40 kg/m2 or ≥ 35 kg/m2 plus comorbidities; average 45.0 kg/m2) and type 2 diabetes who underwent bariatric surgery (Roux-en-Y gastric bypass, 69%; sleeve gastrectomy, 31%) and then had follow-up from January 2010 to June 2017.

  • Investigators assessed participants just before their bariatric surgery and at 1-year after surgery.

Key Results

  • Just 4% were taking magnesium supplementation at baseline, 43% had magnesium deficiency (serum magnesium < 1.52 mEq/L), and average serum magnesium was 1.53 mEq/L.

  • Compared with individuals with baseline magnesium ≥ 1.52 mEq/L, those with magnesium deficiency had higher A1c (7.2% vs 6.4%; P < .001), higher fasting plasma glucose (FPG) (146.2 vs 117.5 mg/dL; P < .001), and on average were taking more glucose-lowering drugs (1.20 vs 0.82; P = .001).

  • One-year post-surgery, among 392 evaluated participants, 78.0% were taking oral magnesium supplementation (100-450 mg/day), the prevalence of magnesium deficiency had dropped to 19%, and mean serum magnesium had risen to 1.62 mEq/L. 

  • As at baseline, those with magnesium deficiency had higher A1c (5.8% vs 5.5%; P < .001), FPG (96.8 vs 89.8 mg/dL; P = .003), and took more glucose-lowering drugs (1.17 vs 0.82; P = .015).

  • Insulin resistance didn't differ by magnesium status at either timepoint.

  • One-year post-bariatric surgery, those taking magnesium supplementation compared with those not taking a supplement had lower A1c (5.5% vs 5.7%; P = .007) and FPG (89.5 vs 93.3 mg/dL; P = .06), with no difference in insulin sensitivity. 

  • Post-bariatric surgery, 229 patients (58%) had total remission of type 2 diabetes. Magnesium levels were higher among those with total versus no remission (1.65 vs 1.58 mEq/L; P < .001).

  • One-year type 2 diabetes remission rates were 62% for those taking magnesium supplementation versus 48% of those not receiving magnesium (P = .06).

  • In multivariate analysis, baseline serum magnesium level independently predicted total remission of type 2 diabetes (odds ratio, 1.37; P < .001). Type of bariatric surgery had no significant link with remission (odds ratio, 0.90; P = .717), but both younger age and lower body mass index at baseline were also significantly linked with remission after surgery.


  • As an observational study, the analysis was subject to potential residual confounding. It is possible that the findings depend in part on variations in diet or the intake of other important nutrients that correlate with magnesium intake.

  • The study cohort received a variety of magnesium supplements and dosages, and intake of magnesium in food was not part of the assessment.


  • The study received no funding.  

  • None of the authors had disclosures.  

This is a summary of a preprint research study, "Higher magnesium levels are associated with better glycemic control and diabetes remission postbariatric surgery," written by researchers primarily at Centro Hospitalar Universitário de São João, Portugal on Research Square provided to you by Medscape. The study has not yet been peer-reviewed. The full text of the study can be found on researchsquare.com.


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