Effect of Oral Magnesium Supplementation on Asthma

Study discusses Magnesium supplementation recommendations and the affects on asthma.

By Carolyn Dean, MD, ND

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Kazaks AG, Uriu-Adams JY, Albertson TE, Shenoy SF, Stern JS. Effect of oral magnesium supplementation on measures of airway resistance and subjective assessment of asthma control and quality of life in men and women with mild to moderate asthma: a randomized placebo controlled trial. J Asthma. 2010 Feb;47(1):83-92.


Randomized, placebo-controlled trial.


Fifty-five men and women ages 21 to 55 years with mild to moderate asthma.

Study Medication and Dosage

Subjects were randomly assigned to one of two groups. Group 1 received 340 mg (170 mg twice per day) of magnesium in the form of magnesium citrate. Group 2 received a placebo. The study ran for 6.5 months.

Main Outcome Measures

Improvement in objective measures of bronchial reactivity (by spirometry) to challenge with methacholine and peak expiratory flow rate (PEFR) and in subjective measures of asthma control and quality of life.

Key Findings

The concentration of methacholine required to cause a 20% drop in forced expiratory volume in minute [FEV(1)] increased significantly from baseline to month 6 within the magnesium group. Meaning that airways were less reactive. PEFR showed a 5.8% predicted improvement over time (P=0.03) in those consuming magnesium. There was significant improvement in AQLQ (Asthma Quality of Life Questionnaire) mean score units (P<0.01) and in overall ACQ (Asthma Control Questionnaire) score in the magnesium group only (P=0.05) after 6.5 months of magnesium.

Practice Implications

This study has huge implications for the prevention and treatment of asthma. It shows improvement in both objective and subjective measures of lung function. However, the authors of the study note that “despite these improvements, researchers reported no significant changes in any of the markers of magnesium status. Magnesium status measurements including serum, erythrocyte, urine, dietary, ionized, and [intravenous].”
This finding could be a problem for doctors who rely on blood testing in order to “prove” that something is working. However, what it proves to me is that the recommended daily allowance (RDA) for magnesium is set far too low. The amount of magnesium used in this study was the standard RDA of 340 mg.
Magnesium has several anti-asthmatic actions, so it is well suited to treat this condition. As a calcium antagonist, it relaxes airways and smooth muscles and dilates the lungs. It also reduces airway inflammation, inhibits chemicals that initiate spasm, and increases anti-inflammatory nitric oxide.
But are we getting enough magnesium? There has been a gradual decline of dietary magnesium in the United States, from a high of 500 mg/day at the turn of the century to barely 175–225 mg/day today.1 The National Academy of Sciences has determined that most American men obtain about 80 percent of the low RDA and women average only 70 percent.2
In one study, a team of researchers identified magnesium deficiency as surprisingly common in asthmatics. Magnesium was low in 65 percent of an intensive care population and in 11 percent of an outpatient population. The study population included 2,633 randomly selected asthmatic adults ages 18 to 70.
A lower dietary magnesium intake was associated with impaired lung function, bronchial hyperreactivity, and an increased risk of wheezing.
A lower dietary magnesium intake was associated with impaired lung function, bronchial hyperreactivity, and an increased risk of wheezing. They concluded that low magnesium intake may be involved in the development of both asthma and chronic obstructive airway disease.3
The subjects of this study had a dietary intake of 83%–85% of the RDA for magnesium. Therefore their 281–296 mg/day was supplemented with 340 mg/day, giving them a daily intake in the 621–636 mg range.
According to researcher Dr. Mildred Seelig, the dosage range for men is 6–8 mg per kg (3.0 to 4.5 mg per pound) of body weight per day. That translates into a total dietary and supplemental magnesium of 600 to 900 mg per day for a 200-pound man. Seelig recommends 6–10 mg/kg/day for athletes, depending on stress and training levels.4
The phrase “depending on stress and training levels” is key, because someone with asthma may have the added burden of
  • being on drug medication that can deplete magnesium;
  • hyperventilating, which can deplete magnesium;
  • stress, which can deplete magnesium;
  • and/oranxiety, which can deplete magnesium.
Another consideration in the treatment of anyone with a magnesium deficiency condition is calcium intake. A woman with asthma taking high doses of calcium for osteoporosis and no supplemental magnesium may further improve her asthma symptoms by lowering calcium intake and moving toward a 2:1 or even 3:1 ratio of magnesium to calcium. This study provided no indication of calcium intake in the participants.
The study authors mention in the introduction that “previous studies of Mg supplementation in adult individuals with asthma have shown little or no improvement in pulmonary function or measures of inflammation. A 3-week intervention trial of 300 mg oral Mg supplementation demonstrated improvement in subjective symptoms and bronchodilator use that were of borderline clinical significance as indicators of asthma control. Neither this study nor a 12-week Mg supplementation study by Fogarty et al. showed improvement in lung function or bronchial reactivity. It is possible that these study periods may not have been of sufficient length to see changes in Mg stores required to affect asthma control.”
Presumably that’s why they chose to perform a 6.5-month study. However, I contend that the 300 mg dose range of magnesium supplementation by most of these studies (which is based on the RDA) is insufficient for the treatment of an asthmatic population given the many ways they can become magnesium deficient. Unfortunately, since we have an inaccurate indication of how much magnesium we need based on the RDA, we don’t know how much magnesium is required and what duration of time is needed to replenish magnesium stores.
This is where clinical practice comes to the fore. In all my research on magnesium, I find it one of the safest supplements used in clinical practice. It does not build up in the tissues like calcium. If a person takes too much, a laxative effect occurs and the excess is eliminated.
If someone experiences the laxative effect before they reach a therapeutic effect of magnesium, various other forms of magnesium including magnesium oil and angstrom-size magnesium may be used. More research should be forthcoming on these two exciting developments in the field magnesium supplementation.

About the Author

Carolyn Dean, MD, ND, author of The Magnesium Miracle (Ballantine Books, 2007) and many other books/booklets, has been at the forefront of natural medicine for more than 30 years. She holds a medical license in California and is a graduate of the Ontario Naturopathic College. She has a complimentary newsletter and an online wellness program called Future Health Now!, which is her answer to the current healthcare crisis. Her web site is www.drcarolyndean.com.


1. Altura BM. Introduction: importance of Mg in physiology and medicine and the need for ion selective electrodes.2. Scand J Clin Lab Invest Suppl. 1994;217:5-9.
3. Institute of Medicine. Dietary Reference Intake for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, D.C.: National Academy Press; 1997.
4. Britton J, Pavord I, Richards K, et al. Dietary magnesium, lung function, wheezing and airway hyperreactivity in a random population sample. Lancet. 1994;344:357-362.
5. Seelig MS. Consequences of magnesium deï¬Âciency on the enhancement of stress reactions; preventive and therapeutic implications (a review). J Am Coll Nutr. 1994;13(5):429-446.