Effect of dietary sodium on the severity of bronchial asthma

Background. A high sodium intake has been found to increase bronchial reactivity in men with asthma. The effects of change in sodium intake on peak flow rate have not been determined. Methods. The effect of changing dietary salt intake for two weeks on the severity of asthma as measured by peak expiratory flow (PEF) was studied in 17 patients with mild asthma in an open randomised crossover trial. PEF measurements were made by the patients in their own homes. Patients were placed on three levels of dietary sodium intake: normal, low, and high. Sodium intake was assessed by 24 hour urine collection. Results. The mean (SD) urine sodium was 147 (45), 84 (32), and 201 (73) mmol/24 hours in the normal, low, and high sodium intake periods respectively. There were no significant differences in PEF or PEF amplitude (highest-lowest PEF), an index of asthma lability, between the three dietary salt periods. Conclusion. A low and high dietary salt intake for two weeks has no effect on peak expiratory flow in patients with mild asthma.