Magnesium and Asthma

Magnesium is a bronchodilator, which means that it opens up the airways. It also reduces inflammation. Magnesium is mainly used to treat severe asthma attacks.1 Magnesium is given intravenously (IV) or with a nebulizer when it is used for emergencies.

Magnesium supplements or magnesium rich-foods have been studied for asthma control. The results have been positive, but do not provide proof that magnesium works.

How is magnesium used to treat severe asthma attacks?

Magnesium is used for life-threatening attacks when other treatments have not worked.1 People are usually on oxygen before they are given magnesium. Most people will have already been treated with short-acting beta-agonists, inhaled ipratropium bromide, and corticosteroids. Magnesium is given to try to avoid putting in a breathing tube.

How well does magnesium work in emergencies?

Magnesium probably reduces hospitalizations.2 However, study results have not been consistent. The 3Mg trial was a large, high-quality study published in 2014.3 It showed that magnesium is not helpful in emergencies. More than 1,100 patients got IV or nebulized magnesium or placebo in the emergency department. People who got IV magnesium had slightly fewer hospital admissions, but the results were not statistically significant. There were no other benefits of IV magnesium. Nebulized magnesium did not work any better than placebo.

On the other hand, a review paper that looked at the 3Mg study together with 13 others had a different conclusion. The authors compared results from 2313 adults with asthma.4 Overall, the people who got magnesium were less likely to be hospitalized for asthma. For every 100 adults treated with magnesium, seven avoided hospitalization. Magnesium also was linked with some improvement in lung function. The main risks of IV magnesium were flushing, fatigue, nausea, headache, and low blood pressure.

Current guidelines recommend magnesium when needed for severe attacks.1,2

Can eating magnesium-rich foods help my asthma?

Magnesium is a mineral. It is found naturally in grains, nuts, green vegetables, and dairy.5 Much of the magnesium in food is lost during processing or cooking. An early study showed that lower magnesium intake was linked with decreased lung function, more airway sensitivity, and more wheeze.5

A few recent studies have tested the idea that taking magnesium can improve asthma. The results were positive, but not enough to prove that magnesium works. One study included 55 adults with moderate but well controlled asthma.6 Most of the participants had normal magnesium blood levels at the start of the study. Half of the participants took a magnesium supplement for 6.5 months, and half got a fake treatment (placebo). The people who took magnesium had less sensitive airways at the end of the study and better peak flow. They also reported fewer symptoms. However, their spirometry results did not improve. Interestingly, there was no difference in blood magnesium levels between the people who took the supplement and placebo. The authors could not explain this result. A study in 37 children also showed that magnesium supplements reduced airway sensitivity.7

Written by: Sarah O'Brien | Last Reviewed: May 2016.
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