Mickleborough 2001.

Methods	Randomised placebo‐controlled cross‐over study.
Participants	16 participants. 8 participants with exercise‐induced asthma (mean age 22 years and all using short beta agonists) and 8 controls (mean age 23 years). The population was recruited from a university population. Exclusion criteria: none of the participants had atopic asthma.
Interventions	All participants entered the study on a normal sodium diet and were started a low sodium diet (65 mmol of sodium using a meal plan). All participants were randomised to a low sodium limb (placebo tablets) or high sodium low chloride limb (174 mmol of sodium a day as sodium bicarbonate) for 2 weeks. After this a 1‐week wash‐out period followed and then participants switched to the alternative diet.
Outcomes	FEV1,FVC, FEV1/FVC pre‐exercise and post‐exercise measurement at 1, 5, 10 and 15 minutes.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Independent investigator had no contact with the subjects and no involvement in data collection or analysis used a computerised random number generator to create the randomisation sequence.
Allocation concealment (selection bias)	Low risk	Randomised study with independent investigator generating the sequence.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as blinded; no other information available.
Incomplete outcome data (attrition bias) All outcomes	Low risk
Selective reporting (reporting bias)	Unclear risk	Not clear from information given.
Other bias	Unclear risk	Participants recruited from a university population. No calculation of power.