A randomized, placebo-controlled study appearing in the Journal of Asthma (2010; 47(1): 83-92) looked at 55 subjects between the ages of 21 and 55, with mild to moderate asthma. They were randomly divided into two groups and given either a placebo or 340 mg of magnesium per day over a 6 1/2 month period.  The severity of the subjects’ asthma was evaluated using pulmonary function testing, methacoline challenge testing and subjective questionnaires about the severity of asthma and the quality of life. The researchers found that the subjects who received the magnesium were much more resistant to the methacoline challenge and also had great improvements on their pulmonary function tests. The magnesium group scored higher on the quality of life questionnaires as well.