Investigation of the effect of short-term change in dietary magnesium intake in asthma.

Randomized, double-blind, placebo-controlled cross-over study in 17 adult nonsmokers with stable asthma. The active-arm group included 10 males and 7 females with mean age 44.8 years; most were receiving inhaled corticosteroids, and all followed a low-magnesium diet during the trial.

Oral magnesium amino acid chelate tablets were given during the active arm. Each tablet contained 200 mg elemental magnesium, and participants took two tablets per day for a total of 400 mg/day for 3 weeks, within a randomized double-blind cross-over trial that also included placebo, a 1 week run-in, and a 1 week wash-out.

Magnesium supplementation improved asthma symptoms, but it did not significantly improve objective lung function or airway reactivity. Symptom scores fell by a median difference of 3.8 (0.5-7.0) points per 7 days with magnesium versus placebo (p=0.02), while bronchodilator use trended lower by 6.0 (-1 to 10.5) doses per 7 days (p=0.051). By contrast, FEV1 did not change significantly (0.072 L, p=0.29), methacholine PD20 was not significantly different (p=0.09), and PEF variability was unchanged (p=0.79). No appreciable adverse effects were reported.

Small sample size (17 participants) and short treatment periods of 3 weeks limit power to detect objective benefits and long-term effects. The cross-over design and low-magnesium diet context may reduce generalizability, and several outcomes were nonsignificant or only borderline, including bronchodilator use and methacholine responsiveness. Some PD20 values were censored, adding uncertainty to airway reactivity interpretation.