Magnesium supplements could help asthmatics, says study
severity of the asthma and used less medication, reports a
randomized clinical trial from Brazil.
The results, the first reported for children, suggest that magnesium has "an important beneficial effect for the control of asthma."
A link between magnesium and bronchodilation was first reported at the start of the twentieth century, and other studies have shown that magnesium can have a relaxing effect on blood vessels.
However studies looking at magnesium supplements and lung health in adults have reported conflicting results, say the researchers.
The new double-blind randomized parallel placebo-controlled study, published on-line in the European Journal of Clinical Nutrition (doi: 10.1038/sj.ejcn.1602475), recruited 37 children and adolescents with moderate persistent asthma (aged between seven and 19, 18 females) and assigned them to receive either magnesium supplements (18 subjects, magnesium 300 mg/day) or placebo (glycine, 19 subjects).
The magnesium supplements were provided by Albion Laboratory.
The patients were allowed to continue to inhale fluticasone (250 micrograms twice a day) and salbutamol (albuterol) if required.
After two months, the researchers, from the University of Campinas and the University of Sao Paulo, found that the children taking the magnesium supplements had, on average, 28 percent fewer days of severe asthma.
According to the American Lung Association, almost 20 million Americans suffer from asthma. The condition is reported to be responsible for over 14 million lost school days in children, while the annual economic cost of asthma is said to be over $16.1bn.
The magnesium supplements were also associated with a reduction in the use of salbutamol, an asthma medication, by the youngsters of almost 40 percent.
The researchers then used the methacholine challenge test PC20 to assess airway responsiveness. This involves the patient inhaling an aerosol of one or more concentrations of methacholine, which constricts the lungs. A positive test is defined as a decrease from the baseline forced expiratory volume in the one second (FEV1) of 20 percent.
After two months of magnesium supplementation, it was found that almost double the concentration of methacholine was needed to induce the 20 percent fall in FEV1, compared to baseline. No significant difference in methacholine concentrations was observed for the placebo group.
"Our results showed that after two months, children and adolescents with moderate persistent asthma who were treated on a regular basis with fluticasone and received oral magnesium supplementation presented a significant improvement in bronchial responsiveness, as assessed by the methacholine test," wrote lead author Clesio Gontijo-Amaral.
The mechanism behind the benefits of the mineral is not clear, say the researchers, and remains to be elucidated.
"To date, magnesium blocks calcium channels, activates sodium and calcium pumps, inhibits the calcium's interaction with myosin and diminish calcium release, altogether promoting a bronchial relaxant effect," said Gontijo-Amaral.
A limitation of the study is the omission of whether or not the children and adolescents followed in this study were magnesium deficient or replete, which could potentially have an impact on whether the findings can be extrapolated to other populations, like the US where most infants and children are said to have adequate intakes of magnesium.
However, according to the US EPA, a substantial proportion of the adolescent population is below the recommended daily intake of the mineral.
The dietary reference intake (DRI) is set at 420 mg/d for magnesium.
Large-scale studies are needed, said the researchers, to further examine the potential role of the mineral for the control of childhood asthma.
