The metallic element magnesium is also very important to human metabolism.1 Use of magnesium as a supplement is probably most well known in such laxative preparations as milk of magnesia. In more emergent scenarios, IV magnesium is used in cases of pre-eclampsia and preterm labor. Recent research links magnesium to more than 300 enzyme systems and points to its role in maintaining a balance in many other elemental combinations.2 Magnesium is essential for the formation of the cellular chemical powerhouse cyclic adenosine monophospate.3


Serum magnesium exists in three different forms: (1) protein-bound; (2) complexed; and (3) free ionic.3 Unbound ionic magnesium is available in the body to move freely into systems to fulfill an increased demand caused by illness or other stress. In the human body, 60% of stored magnesium is found in bone and 38% in skeletal muscle and other soft tissues, leaving only 1% to 2% floating free in the bloodstream.4 Magnesium also controls several balances with other elements, including calcium, phosphorus, potassium, and insulin.


Many of the conditions that magnesium supplementation benefits involve muscular or vascular tone. Decreased magnesium levels have been studied in relation to migraines, asthma, and preterm labor. Magnesium supplementation is considered “effective” in the treatment of constipation and heartburn; “likely effective” in pre-eclampsia; and “possibly effective” for cardiac arrhythmia, asthma, and migraines.1

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Magnesium deficiency is related to lifestyle and dietary changes.5 An estimated 20% of the U.S. population consumes less than two-thirds of the recommended daily allowance (RDA).6 Magnesium is best absorbed when consumed in foods that contain high levels of the element. Although the list is long, in general, a food high in fiber is also likely high in magnesium (e.g., beans, vegetables, seeds, and nuts).4

Of all the conditions affected by low levels of magnesium, type 2 diabetes is the most common. One meta-analysis found that dietary magnesium is inversely related to the occurrence of this disease.7 This was corroborated by another prospective cohort study that compared incidence of type 2 diabetes with specific dietary interventions. Whole-grain products were shown to result in the most significant reduction in diabetes, whereas fruits and vegetables were more marginal.8

In another study, participants were given a daily oral supplement of magnesium salt for 30 days and monitored for changes in diabetic parameters. While the typical measures of hemoglobin A1c, BP, and lipid levels trended lower, the changes were not statistically significant. However, the degree of insulin sensitivity did improve, leading to speculation that magnesium supplementation lowers plasma glucose levels by reducing cellular insulin resistance.5
Physiologically, magnesium affects BP by facilitating the endothelial resting tone and smooth-muscle reactivity.9 Magnesium also exerts a mild calcium channel blockade and reduces inflammation and oxidative stress.10 In a review of 12 clinical trials involving participants with verified hypertension, magnesium supplementation was used to determine impact on BP. The results showed no statistically significant reduction in systolic BP, but did show an impressive reduction in diastolic BP.11

Magnesium deficiency becomes acutely problematic in pregnancy. Magnesium plays a role in fetal growth and development and is essential in controlling uterine-muscle-wall excitability.6 Preterm labor is thought to be related to low magnesium levels and is the most common condition treated with acute supplementation.6

Dose, how supplied, cost

The RDA for magnesium is 420 mg/day for adult men and 320 mg/day for women.6 For optimal absorption, magnesium supplementation must be accompanied by vitamin B6.6

Safety and drug interactions

Persons with normal renal function are unlikely to accumulate a toxic level of magnesium. Magnesium blocks the absorption of antibiotics in the fluoroquinolone and tetracycline families as well as calcium channel blocking cardiovascular drugs and levothyroxine.12   


Data in support of magnesium’s effectiveness in the treatment of diabetes and hypertension is very exciting. Just as other everyday vitamins and minerals have been found to be major factors in disease, magnesium holds similar potential. Patients with no obvious contraindication to supplementation should certainly consider magnesium to treat their diabetes, hypertension, or asthma.


1. Natural Medicines Comprehensive Database. Magnesium.

2. Cowan JA. Structural and catalytic chemistry of magnesium-dependent enzymes. Biometals. 2002;15:225-235.

3. Maguire ME, Cowan JA. Magnesium chemistry and biochemistry. Biometals. 2002;15:203-210.

4. Office of Dietary Supplements. Dietary supplement fact sheet: Magnesium.

5. Yokota K, Kato M, Lister F, et al. Clinical efficacy of magnesium supplementation in patients with type 2 diabetes.
J Am Coll Nutr. 2004;23:506S-509S.

6. Durlach J. New data on the importance of gestational Mg deficiency. J Am Coll Nutr. 2004 Dec;23(6):694S-700S.

7. Larsson SC, Wolk A. Magnesium intake and risk of type 2 diabetes: a meta-analysis. J Intern Med. 2007;262:208-214.

8. Schulze MB, Schulz M, Heidemann C, et al. Fiber and magnesium intake and incidence of type 2 diabetes: a prospective study  and meta-analysis. Arch Intern Med. 2007 May 14;167(9):956-65.

9. Sontia B, Touyz RM. Role of magnesium in hypertension. Arch Biochem Biophys. 2007;458:33-39.

10. Bo S, Pisu E. Role of dietary magnesium in cardiovascular disease prevention, insulin sensitivity and diabetes. Curr Opin Lipidol. 2008;19:50-56.

11. Beyer FR, Dickinson HO, Nicolson DJ, et al. Combined calcium, magnesium and potassium supplementation for the management of primary hypertension in adults. Cochrane Database Syst Rev. 2006;3:CD004805.

12. University of Maryland Medical Center. Magnesium.

All electronic documents accessed October 15, 2010.