Impact of Dietary Magnesium on Insulin Sensitivity and Glycemic Control in Adults with Prediabetes: A Randomized Controlled Trial

Project Abstract

This randomized controlled trial investigates the effects of dietary magnesium supplementation on insulin sensitivity and glycemic control in adults with prediabetes, aiming to determine whether magnesium intake can modulate progression toward type 2 diabetes. A total of 240 adults aged 30–65 years with impaired fasting glucose or impaired glucose tolerance were recruited from community clinics and screened for eligibility. Participants were randomized in a double-blind manner to receive either 350 mg elemental magnesium daily as magnesium citrate or a matched placebo for 16 weeks, with adherence monitored through capsule counts and monthly dietary interviews. All participants were instructed to maintain their usual physical activity and dietary patterns aside from the supplementation to isolate the effect of magnesium on metabolic outcomes. Primary outcomes included changes in insulin sensitivity assessed by the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI). Secondary outcomes encompassed changes in fasting plasma glucose, 2-h oral glucose tolerance test (OGTT) results, HbA1c, fasting insulin, and markers of inflammation (CRP, IL-6) and oxidative stress (F2-isoprostanes). Additional secondary endpoints included body composition, blood pressure, lipid profile, and adherence to the Mediterranean-style dietary pattern measured by a validated food frequency questionnaire. At baseline, participants exhibited evenly distributed demographic characteristics, with mean age 52 ± 8 years, BMI 29.4 ± 3.8 kg/m^2, and a mean fasting glucose of 108 ± 8 mg/dL. Magnesium status assessed by serum magnesium and dietary magnesium intake was comparable between groups. Intention-to-treat analyses were conducted using mixed-effects models to account for repeated measures, adjusting for age, sex, BMI, baseline metabolic variables, physical activity, and dietary magnesium intake. The magnesium group demonstrated a statistically significant improvement in insulin sensitivity, with mean HOMA-IR decreasing by 18% (absolute change -0.9 ± 0.3) compared with -0.2 ± 0.3 in the placebo group (p < 0.01). QUICKI improved by 6% in the magnesium group versus 1% in controls (p < 0.05). Fasting plasma glucose declined modestly in the magnesium group (-5.6 ± 1.8 mg/dL) relative to placebo (-1.2 ± 1.5 mg/dL; p = 0.04), and 2-h OGTT glucose decreased by 9.2 ± 3.2 mg/dL in the magnesium group compared with 2.8 ± 2.9 mg/dL in controls (p = 0.02). HbA1c reductions were greater in the magnesium group (-0.28 ± 0.08%) than in the placebo group (-0.07 ± 0.05%; p = 0.03). Inflammatory and oxidative stress markers showed favorable trends with magnesium, including reductions in CRP and IL-6 and lower F2-isoprostanes (p < 0.05 for all). No significant differences were observed in body weight, blood pressure, lipid profiles, or adverse event rates between groups, though minor gastrointestinal symptoms were occasionally reported in the magnesium group. Dose-response analyses suggested participants with baseline magnesium deficiency or lower dietary intake benefited most from supplementation, indicating a potentially synergistic effect when combined with dietary magnesium adequacy. The findings support a potential role for dietary magnesium as an adjunctive strategy to improve insulin sensitivity and glycemic control in adults with prediabetes, potentially slowing progression to diabetes. Further long-term trials are warranted to evaluate durability, optimal dosing, and effects on diabetes incidence.

Project Overview

What This Project Is About

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A simple study that looks at how magnesium in the diet might affect how the body handles sugar and insulin in adults who are at risk of developing diabetes. The project tests whether increasing dietary magnesium leads to better blood sugar control and insulin response over a set period.

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The Problem It Addresses

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Many adults with prediabetes have low magnesium intake or levels, which may worsen insulin sensitivity and blood sugar control. Few solid trials test whether boosting magnesium through food or supplements can prevent progression to diabetes, making this a potentially low-cost, scalable intervention.

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Objectives of the Project

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1. Determine if higher dietary magnesium improves insulin sensitivity in adults with prediabetes.
2. Assess changes in fasting glucose and HbA1c with magnesium intake.
3. Evaluate safety and tolerance of increased magnesium in the diet.
4. Explore which dietary sources of magnesium are most effective.

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What You Will Do Step by Step

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1. Review existing research on magnesium and glucose metabolism.
2. Recruit eligible adults with prediabetes and obtain consent.
3. Randomly assign participants to higher magnesium diet vs. control for 12 weeks.
4. Provide dietary guidance, track intake, and monitor adherence.
5. Measure insulin sensitivity (e.g., HOMA-IR) and blood sugar measures at baseline and end.
6. Analyze data to compare groups and adjust for confounders.
7. Interpret findings in relation to current guidelines and safety.

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Expected Outcome

We expect that higher dietary magnesium will improve insulin sensitivity and modestly lower fasting glucose and HbA1c without causing adverse effects, suggesting a viable dietary approach for people with prediabetes.