Supplementing with magnesium has been popular in recent years and is claimed to improve health in many ways.
Not all of these claims are backed by science, but there is convincing evidence linking magnesium supplementation to a lower risk of type 2 diabetes.
A recent meta-analysis examined the effects of magnesium supplementation in diabetics or people at a high risk of developing type 2 diabetes. Here is a summary of its findings.
Observational studies suggest that magnesium insufficiency or deficiency is linked with heart disease and several metabolic disorders, including hypertension, metabolic syndrome and type 2 diabetes (T2D) (1, 2, 3).
One large meta-analysis of observational studies including more than half a million participants showed that higher magnesium intake was associated with a lower risk of T2D (4).
However, the direction of causality is unclear. Diabetes might promote magnesium depletion or, alternatively, magnesium deficiency might increase the risk of T2D.
Randomized controlled trials support the second option. They show that supplementing with magnesium improves the symptoms of T2D, indicating that poor dietary intake of magnesium may, at least partly, contribute to its development (7).
But there is also some evidence suggesting that T2D may increase magnesium depletion, creating a vicious cycle (8).
This was a meta-analysis of randomized controlled trials examining the effects of magnesium supplementation on blood sugar control in people with type 2 diabetes (T2D) or those at a high risk of developing it.
This was a systematic review and meta-analysis of randomized controlled trials examining the effects of magnesium supplementation on markers of blood sugar control and insulin sensitivity.
The researchers searched for relevant articles using five of the largest scientific databases.
The inclusion criteria were the following:
- A double-blind, randomized controlled trial.
- Participants were diabetic or at a high risk of developing T2D.
- The studies examined oral magnesium supplementation.
- Outcomes included markers of glucose metabolism or insulin sensitivity.
A total of 18 randomized controlled trials fulfilled all of the inclusion criteria — 12 studies included people with T2D and 6 included people at a high risk of diabetes.
Bottom Line: This was a meta-analysis of randomized controlled trials examining the association of magnesium supplementation with blood sugar control in diabetics or people at a high risk of developing type 2 diabetes.
Finding 1: Magnesium Reduced Fasting Blood Sugar Levels
The analysis showed that supplementing with magnesium significantly reduced fasting blood sugar levels in people with T2D or at a high risk of it, compared to a placebo.
Specifically, the standard mean difference was -0.4, which means that magnesium caused a moderate improvement (decrease) in blood sugar levels.
However, magnesium did not affect fasting blood sugar levels in people who didn’t have type 2 diabetes.
Additionally, levels of fasting insulin, insulin sensitivity (HOMA-IR) or HbA1c didn’t change significantly.
Bottom Line: Supplementing with magnesium reduced fasting blood sugar levels in people with type 2 diabetes.
Finding 2: Magnesium Reduced the Rise in Blood Sugar After Eating Sugar
An oral glucose tolerance test (OGTT) measures the changes in blood sugar after eating a dose of pure sugar (glucose). It is currently the gold standard for diagnosing diabetes.
Three of the included studies investigated the effects of magnesium on blood sugar levels during an OGTT in people at a high risk of developing diabetes.
Based on these studies, the researchers concluded that supplementing with magnesium significantly reduces blood sugar levels after eating sugar.
Specifically, the standard mean difference was -0.35, which is a moderate effect.
These findings were supported by one study that measured OGT in diabetics (9).
Bottom Line: Supplementing with magnesium significantly reduced the rise in blood sugar during an oral glucose tolerance test.
Finding 3: High Magnesium Levels Associated With Lower HbA1c Levels in Diabetics
Glycated hemoglobin (HbA1c) is a marker of the previous three-month average in blood sugar levels.
Analyses revealed that high magnesium levels correlated with lower levels of glycated hemoglobin (HbA1c) in people with T2D, supporting the overall findings of the meta-analysis.
However, supplementing with magnesium did not affect HbA1c levels, probably because changes in HbA1c are slow and many of the studies were short in duration.
Magnesium status was also associated with improved insulin sensitivity in people at a high risk of T2D, but no significant links were detected in diabetics.
Bottom Line: Observational studies showed that high magnesium levels were linked with lower HbA1c levels in diabetics.
How Does Magnesium Deficiency Impair Blood Sugar Control?
The meta-analysis strongly suggests that supplementing with magnesium benefits diabetics and those at a high risk of it.
There are several mechanisms by which magnesium insufficiency could impair blood sugar control.
- Sustained magnesium deficiency appears to reduce blood sugar uptake (10, 11).
- Low magnesium levels may impair insulin release from the beta-cells in the pancreas (12, 13).
- Poor magnesium status might increase oxidative stress, possibly increasing insulin resistance (10).
Bottom Line: Magnesium deficiency could impair blood sugar control by reducing sugar uptake (insulin sensitivity), impairing insulin release and/or increasing oxidative stress.
This meta-analysis seems to have been designed well, and it followed accepted guidelines.
Although the included trials were generally high-quality, they included few participants and were generally short in duration. Long-term trials are needed.
Finally, the included studies varied in their design. For example, the doses of magnesium, as well as its form, differed considerably across studies.
Bottom Line: The included studies were generally of short duration, and their designs varied.
Summary and Real-Life Application
The researchers concluded that supplementing with magnesium may improve blood sugar control in diabetics, as well as people at a high risk of developing diabetes.
If you are diabetic or at risk of developing diabetes, supplementing with magnesium may be a good idea. However, you can also get all the magnesium you need from whole foods.
Magnesium-rich foods include whole grains, nuts, seeds, beans, dark leafy greens and fish. It is also abundant in coffee, cocoa and dark chocolate.