Following a low-sodium diet does not appear to have any appreciable impact on asthma control, according to new research.
Contrary to past studies - which have suggested a link between low-sodium diets and improved asthma control - a new study by researchers at The University of Nottingham found no evidence that cutting back on salt helps patients with their symptoms.
Dr Zara Pogson, clinical research fellow at The University of Nottingham, said: "Despite the clear benefit of a low-sodium diet on cardiovascular risk factors, there is no therapeutic benefit in the use of a low-sodium diet…on asthma control in our study population."
The results of the randomised, double-blind, placebo-controlled trial were published in the second issue for July of the American Journal of Respiratory and Critical Care Medicine by the American Thoracic Society.
Nearly 200 subjects completed the study which compared the effect of changes in bronchial reactivity - a measure of asthma activity - on asthma patients who followed a strict low-sodium diet. Each subject either received sodium supplements to approximate normal sodium intake of 80 millimoles per litre (mmol) a day, or a placebo, for six weeks.
Dr Pogson and colleagues hypothesized that the subjects on the low sodium intake would show improved clinical control of asthma symptoms based on a test of asthma activity, measures of lung function, asthma symptoms and use of asthma medication. Contrary to their hypothesis, however, they detected no differences in any measures of asthma between the groups.
"We observed no difference in the outcome measures related to asthma activity in adults with asthma and bronchial reactivity who adopted a low-sodium diet for six weeks compared with those who did not, despite a final difference in daily sodium excretion of 50 mmol," wrote Dr Pogson.